# Source code for apsw.ext

    # Provides various useful routines

    from __future__ import annotations

    import abc
    import collections
    import collections.abc
    import contextvars
    import dataclasses
    import enum
    import functools
    import html
    import inspect
    import keyword
    import logging
    import math
    import os
    import re
    import string
    import sys
    import time
    import traceback
    import types
    from dataclasses import dataclass, is_dataclass, make_dataclass
    from fractions import Fraction
    from typing import Any, Callable, Generator, Iterable, Iterator, Literal, Sequence, TextIO, Union

    import apsw
    import apsw.unicode

    NoneType = types.NoneType if sys.version_info > (3, 10) else type(None)

    def result_string(code: int) -> str:
        """Turns a result or extended result code into a string.
        The appropriate mapping based on the value is used."""
        if code < 256:
            return apsw.mapping_result_codes.get(code, str(code))  # type: ignore
        return apsw.mapping_extended_result_codes.get(code, str(code))  # type: ignore

    class DataClassRowFactory:
        """Returns each row as a :mod:`dataclass <dataclasses>`, accessible by column name.

        To use set an instance as :attr:`Connection.row_trace
        <apsw.Connection.row_trace>` to affect all :class:`cursors
        <apsw.Cursor>`, or on a specific cursor::

            connection.row_trace = apsw.ext.DataClassRowFactory()
            for row in connection.execute("SELECT title, sum(orders) AS total, ..."):
                # You can now access by name
                print (row.title, row.total)
                # you can get the underlying description
                print (row.__description__)

        You can use as many instances of this class as you want, each across as many
        :class:`connections <apsw.Connection>` as you want.

        :param rename:     Column names could be duplicated, or not
            valid in Python (eg a column named `continue`).
            If `rename` is True, then invalid/duplicate names are replaced
            with `_` and their position starting at zero.  For example `title,
            total, title, continue` would become `title, total, _2, _3`.  If
            `rename` is False then problem column names will result in
            :exc:`TypeError` raised by :func:`dataclasses.make_dataclass`

        :param dataclass_kwargs: Additional parameters when creating the dataclass
           as described in :func:`dataclasses.dataclass`.  For example you may
           want `frozen = True` to make the dataclass read-only, or `slots = True`
           to reduce memory consumption.

        """

        def __init__(self, *, rename: bool = True, dataclass_kwargs: dict[str, Any] | None = None):
            self.dataclass_kwargs = dataclass_kwargs or {}
            self.rename = rename

        @functools.lru_cache(maxsize=16)
        def get_dataclass(self, description: tuple[tuple[str, str], ...]) -> tuple[Any, tuple[str, ...]]:
            """Returns dataclass and tuple of (potentially renamed) column names

            The dataclass is what is returned for each row with that
            :meth:`description <apsw.Cursor.get_description>`

            This method caches its results.
            """
            names = [d[0] for d in description]
            if self.rename:
                new_names: list[str] = []
                for i, n in enumerate(names):
                    if n.isidentifier() and not keyword.iskeyword(n) and n not in new_names:
                        new_names.append(n)
                    else:
                        new_names.append(f"_{ i }")
                names = new_names
            types = [self.get_type(d[1]) for d in description]

            kwargs = self.dataclass_kwargs.copy()
            if "namespace" not in kwargs:
                kwargs["namespace"] = {}
            kwargs["namespace"]["__description__"] = description

            # some magic to make the reported classnames different
            suffix = (".%06X" % hash(repr(description)))[:7]

            return make_dataclass(f"{ self.__class__.__name__ }{ suffix }", zip(names, types), **kwargs), tuple(names)

        def get_type(self, t: str | None) -> Any:
            """Returns the :mod:`type hint <typing>` to use in the dataclass based on the type in the :meth:`description <apsw.Cursor.get_description>`

            `SQLite's affinity rules  <https://www.sqlite.org/datatype3.html#affname>`__ are followed.

            The values have no effect on how your program runs, but can be used by tools like
            mypy.  Column information like whether `null` is allowed is not present, so
            this is just a hint.
            """
            if not t:
                return Any
            # From 3.1 https://www.sqlite.org/datatype3.html
            t = t.upper()
            if "INT" in t:
                return int
            if "CHAR" in t or "CLOB" in t or "TEXT" in t:
                return str
            if "BLOB" in t:
                return bytes
            if "REAL" in t or "FLOA" in t or "DOUB" in t:
                return float
            return Union[float, int]

        def __call__(self, cursor: apsw.Cursor, row: apsw.SQLiteValues) -> Any:
            """What the row tracer calls

            This :meth:`looks up <get_dataclass>` the dataclass and column
            names, and then returns an instance of the dataclass.
            """
            dc, column_names = self.get_dataclass(cursor.get_description())
            return dc(**dict(zip(column_names, row)))

    class SQLiteTypeAdapter(abc.ABC):
        """A metaclass to indicate conversion to SQLite types is supported

        This is one way to indicate your type supports conversion to a
        value supported by SQLite.  You can either inherit from this class,
        or call the register method::

           apsw.ext.SQLiteTypeAdapter.register(YourClassHere)

        Doing either is entirely sufficient and there is no need to
        register with :class:`TypesConverterCursorFactory`
        """

        @abc.abstractmethod
        def to_sqlite_value(self) -> apsw.SQLiteValue:
            "Return a SQLite compatible value for this object"
            raise NotImplementedError

    class TypesConverterCursorFactory:
        """Provides cursors that can convert objects into one of the types supported by SQLite,
        or back from SQLite

        :param abstract_base_class: Which metaclass to consider as conversion capable
        """

        def __init__(self, abstract_base_class: abc.ABCMeta = SQLiteTypeAdapter):
            self.abstract_base_class = abstract_base_class
            # to sqlite value
            self.adapters: dict[type, Callable[[Any], apsw.SQLiteValue]] = {}
            # from sqlite value
            self.converters: dict[str, Callable[[apsw.SQLiteValue], Any]] = {}

        def register_adapter(self, klass: type, callable: Callable[[Any], apsw.SQLiteValue]) -> None:
            """Registers a callable that converts from `klass` to one of the supported SQLite types"""
            self.adapters[klass] = callable

        def register_converter(self, name: str, callable: Callable[[apsw.SQLiteValue], Any]) -> None:
            """Registers a callable that converts from a SQLite value"""
            self.converters[name] = callable

        def __call__(self, connection: apsw.Connection) -> TypeConverterCursor:
            "Returns a new convertor :class:`cursor <apsw.Cursor>` for the `connection`"
            return TypesConverterCursorFactory.TypeConverterCursor(connection, self)

        def adapt_value(self, value: Any) -> apsw.SQLiteValue:
            "Returns SQLite representation of `value`"
            if value is None or isinstance(value, (int, bytes, str, float)):
                return value
            if isinstance(value, self.abstract_base_class):
                return value.to_sqlite_value()
            adapter = self.adapters.get(type(value))
            if not adapter:
                raise TypeError(f"No adapter registered for type { type(value) }")
            return adapter(value)

        def convert_value(self, schematype: str, value: apsw.SQLiteValue) -> Any:
            "Returns Python object from schema type and SQLite value"
            converter = self.converters.get(schematype)
            if not converter:
                return value
            return converter(value)

        def wrap_bindings(self, bindings: apsw.Bindings | None) -> apsw.Bindings | None:
            "Wraps bindings that are supplied to underlying execute"
            if bindings is None:
                return None
            if isinstance(bindings, (dict, collections.abc.Mapping)):
                return TypesConverterCursorFactory.DictAdapter(self, bindings)  # type: ignore[arg-type]
            return tuple(self.adapt_value(v) for v in bindings)

        def wrap_sequence_bindings(
            self, sequenceofbindings: Iterable[apsw.Bindings]
        ) -> Generator[apsw.Bindings, None, None]:
            "Wraps a sequence of bindings that are supplied to the underlying executemany"
            for binding in sequenceofbindings:
                yield self.wrap_bindings(binding)  # type: ignore[misc]

        class DictAdapter(collections.abc.Mapping):
            "Used to wrap dictionaries supplied as bindings"

            def __init__(self, factory: TypesConverterCursorFactory, data: collections.abc.Mapping[str, apsw.SQLiteValue]):
                self.data = data
                self.factory = factory

            def __getitem__(self, key: str) -> apsw.SQLiteValue:
                return self.factory.adapt_value(self.data[key])

            def __iter__(self):
                "Required by mapping, but not used"
                raise NotImplementedError

            def __len__(self):
                "Required by mapping, but not used"
                raise NotImplementedError

        class TypeConverterCursor(apsw.Cursor):
            "Cursor used to do conversions"

            def __init__(self, connection: apsw.Connection, factory: TypesConverterCursorFactory):
                super().__init__(connection)
                self.factory = factory
                self.row_trace = self._rowtracer

            def _rowtracer(self, cursor: apsw.Cursor, values: apsw.SQLiteValues) -> tuple[Any, ...]:
                return tuple(self.factory.convert_value(d[1], v) for d, v in zip(cursor.get_description(), values))

            def execute(
                self,
                statements: str,
                bindings: apsw.Bindings | None = None,
                *,
                can_cache: bool = True,
                prepare_flags: int = 0,
                explain: int = -1,
            ) -> apsw.Cursor:
                """Executes the statements doing conversions on supplied and returned values

                See :meth:`apsw.Cursor.execute` for parameter details"""
                return super().execute(
                    statements,
                    self.factory.wrap_bindings(bindings),
                    can_cache=can_cache,
                    prepare_flags=prepare_flags,
                    explain=explain,
                )

            def executemany(
                self,
                statements: str,
                sequenceofbindings: Iterable[apsw.Bindings],
                *,
                can_cache: bool = True,
                prepare_flags: int = 0,
                explain: int = -1,
            ) -> apsw.Cursor:
                """Executes the statements against each item in sequenceofbindings, doing conversions on supplied and returned values

                See :meth:`apsw.Cursor.executemany` for parameter details"""
                return super().executemany(
                    statements,
                    self.factory.wrap_sequence_bindings(sequenceofbindings),  # type: ignore[arg-type]
                    can_cache=can_cache,
                    prepare_flags=prepare_flags,
                    explain=explain,
                )

    def log_sqlite(*, level: int = logging.ERROR, logger: logging.Logger | None = None) -> None:
        """Send SQLite `log messages <https://www.sqlite.org/errlog.html>`__ to :mod:`logging`

        :param level: highest `level <https://docs.python.org/3/library/logging.html#levels>`__ to log at
        :param logger: Use the specific logger
        """

        def handler(errcode: int, message: str) -> None:
            nonlocal level
            err_str = result_string(errcode)
            extra = {"sqlite_code": errcode, "sqlite_code_name": err_str, "sqlite_message": message}
            # Level defaults to ERROR but some messages aren't as important
            if errcode & 0xFF == apsw.SQLITE_WARNING:
                level = min(level, logging.WARNING)
            elif errcode & 0xFF == apsw.SQLITE_NOTICE:
                # these are really half way between INFO and WARNING and
                # current instances are recovering journals/WAL etc which
                # happens if the previous process exited abruptly.
                level = min(level, logging.WARNING)
            elif errcode == apsw.SQLITE_SCHEMA:
                # these happen automatically without developer control,
                # especially when using FTS5.  DEBUG is almost more
                # appropriate!
                level = min(level, logging.INFO)

            (logger or logging).log(level, "SQLITE_LOG: %s (%d) %s", message, errcode, err_str, extra=extra)

        apsw.config(apsw.SQLITE_CONFIG_LOG, handler)

    def print_augmented_traceback(
        exc_type: type[BaseException],
        exc_value: BaseException,
        exc_traceback: types.TracebackType,
        *,
        file: TextIO | None = None,
    ) -> None:
        """Prints a standard exception, but also includes the value of variables in each stack frame
        which APSW :ref:`adds <augmentedstacktraces>` to help diagnostics and debugging.

        :param exc_type: The exception type
        :param exc_value: The exception value
        :param exc_traceback: Traceback for the exception
        :param file: (default ``sys.stderr``) Where the print goes

        .. code-block::

            try:
                ....
            except Exception as exc:
                apsw.ext.print_augmented_traceback(*sys.exc_info())
        """

        file = file or sys.stderr

        tbe = traceback.TracebackException(exc_type, exc_value, exc_traceback, capture_locals=True, compact=True)
        for line in tbe.format():
            print(line, file=file)

    def index_info_to_dict(
        o: apsw.IndexInfo, *, column_names: list[str] | None = None, rowid_name: str = "__ROWID__"
    ) -> dict[str, Any]:
        """
        Returns a :class:`apsw.IndexInfo` as a dictionary.

        If *column_names* is supplied then additional keys with column
        names are present, using *rowid_name* for the rowid.

        Here is an example response::

            query = '''
                SELECT orderid, note FROM sales WHERE
                        price > 74.99
                        AND quantity<=?
                        AND customer in ('Acme Widgets', 'Acme Industries')
                ORDER BY date desc
                LIMIT 10'''

            {'aConstraint': [{'collation': 'BINARY',
                            'iColumn': 5,
                            'iColumn_name': 'price',
                            'op': 4,
                            'op_str': 'SQLITE_INDEX_CONSTRAINT_GT',
                            'rhs': 74.99,
                            'usable': True},
                            {'collation': 'BINARY',
                            'iColumn': 7,
                            'iColumn_name': 'quantity',
                            'op': 8,
                            'op_str': 'SQLITE_INDEX_CONSTRAINT_LE',
                            'rhs': None,
                            'usable': True},
                            {'collation': 'BINARY',
                            'iColumn': 8,
                            'iColumn_name': 'customer',
                            'op': 2,
                            'op_str': 'SQLITE_INDEX_CONSTRAINT_EQ',
                            'rhs': None,
                            'usable': True},
                            {'collation': 'BINARY',
                            'op': 73,
                            'op_str': 'SQLITE_INDEX_CONSTRAINT_LIMIT',
                            'rhs': 10,
                            'usable': True}],
            'aConstraintUsage': [{'argvIndex': 0, 'in': False, 'omit': False},
                                {'argvIndex': 0, 'in': False, 'omit': False},
                                {'argvIndex': 0, 'in': True, 'omit': False},
                                {'argvIndex': 0, 'in': False, 'omit': False}],
            'aOrderBy': [{'desc': True, 'iColumn': 9, 'iColumn_name': 'date'}],
            'colUsed': {0, 3, 5, 7, 8, 9},
            'colUsed_names': {'date', 'note', 'customer', 'quantity', 'orderid', 'price'},
            'distinct': 0,
            'estimatedCost': 5e+98,
            'estimatedRows': 25,
            'idxFlags': 0,
            'idxFlags_set': set(),
            'idxNum': 0,
            'idxStr': None,
            'nConstraint': 4,
            'nOrderBy': 1,
            'orderByConsumed': False}
        """

        res = {
            "nConstraint": o.nConstraint,
            "aConstraint": [
                {
                    "iColumn": o.get_aConstraint_iColumn(n),
                    "op": o.get_aConstraint_op(n),
                    "op_str": apsw.mapping_bestindex_constraints.get(o.get_aConstraint_op(n)),
                    "usable": o.get_aConstraint_usable(n),
                    "collation": o.get_aConstraint_collation(n),
                    "rhs": o.get_aConstraint_rhs(n),
                }
                for n in range(o.nConstraint)
            ],
            "nOrderBy": o.nOrderBy,
            "aOrderBy": [
                {
                    "iColumn": o.get_aOrderBy_iColumn(n),
                    "desc": o.get_aOrderBy_desc(n),
                }
                for n in range(o.nOrderBy)
            ],
            "aConstraintUsage": [
                {
                    "argvIndex": o.get_aConstraintUsage_argvIndex(n),
                    "omit": o.get_aConstraintUsage_omit(n),
                    "in": o.get_aConstraintUsage_in(n),
                }
                for n in range(o.nConstraint)
            ],
            "idxNum": o.idxNum,
            "idxStr": o.idxStr,
            "orderByConsumed": o.orderByConsumed,
            "estimatedCost": o.estimatedCost,
            "estimatedRows": o.estimatedRows,
            "idxFlags": o.idxFlags,
            "idxFlags_set": set(
                v for k, v in apsw.mapping_virtual_table_scan_flags.items() if isinstance(k, int) and o.idxFlags & k
            ),
            "colUsed": o.colUsed,
            "distinct": o.distinct,
        }

        for aConstraint in res["aConstraint"]:  # type: ignore[attr-defined]
            if aConstraint["op"] in (apsw.SQLITE_INDEX_CONSTRAINT_OFFSET, apsw.SQLITE_INDEX_CONSTRAINT_LIMIT):
                del aConstraint["iColumn"]
            if aConstraint["op"] >= apsw.SQLITE_INDEX_CONSTRAINT_FUNCTION and aConstraint["op"] <= 255:
                aConstraint["op_str"] = (
                    f"SQLITE_INDEX_CONSTRAINT_FUNCTION+{ aConstraint['op'] - apsw.SQLITE_INDEX_CONSTRAINT_FUNCTION }"
                )

        if column_names:
            for aconstraint in res["aConstraint"]:  # type: ignore[attr-defined]
                if "iColumn" in aconstraint:
                    aconstraint["iColumn_name"] = (
                        rowid_name if aconstraint["iColumn"] == -1 else column_names[aconstraint["iColumn"]]
                    )
            for aorderby in res["aOrderBy"]:  # type: ignore[attr-defined]
                aorderby["iColumn_name"] = rowid_name if aorderby["iColumn"] == -1 else column_names[aorderby["iColumn"]]
            # colUsed has all bits set when SQLite just wants the whole row
            # eg when doing an update
            res["colUsed_names"] = set(column_names[i] for i in o.colUsed if i < len(column_names))
            if 63 in o.colUsed:  # could be one or more of the rest - we add all
                res["colUsed_names"].update(column_names[63:])  # type: ignore[attr-defined]

        return res

    def dbinfo(
        db: apsw.Connection, schema: str = "main"
    ) -> tuple[DatabaseFileInfo | None, JournalFileInfo | WALFileInfo | None]:
        """Extracts fields from the database, journal, and wal files

        Based on the `file format description <https://www.sqlite.org/fileformat2.html>`__.  The
        headers are read using :meth:`apsw.Connection.read` so you see inside encrypted, compressed,
        zip etc formats, not necessarily the actual on disk file.

        Memory databases return `None` for both.
        """

        dbinfo: DatabaseFileInfo | None = None
        journalinfo: JournalFileInfo | WALFileInfo | None = None

        try:
            ok, header_page = db.read(schema, 0, 0, 128)
        except apsw.SQLError:
            ok = False

        be_int = functools.partial(int.from_bytes, byteorder="big", signed=False)

        be_sint = functools.partial(int.from_bytes, byteorder="big", signed=True)

        def be_bool(b: bytes) -> bool:
            return bool(be_int(b))

        def be_page_size(b: bytes) -> int:
            v = be_int(b)
            if v == 1:
                v = 65536
            return v

        def text_encoding(b: bytes) -> str:
            v = be_int(b)
            return {0: "(pending)", 1: "UTF-8", 2: "UTF-16le", 3: "UTF-16be"}.get(v, f"<< INVALID VALUE { v } >>")

        if ok:
            kw: dict[str, Any] = {"filename": db.filename}
            for name, offset, size, converter in (
                ("header", 0, 16, bytes),
                ("page_size", 16, 2, be_page_size),
                ("write_format", 18, 1, be_int),
                ("read_format", 19, 1, be_int),
                ("reserved_bytes", 20, 1, be_int),
                ("file_change_counter", 24, 4, be_int),
                ("page_count", 28, 4, be_int),
                ("freelist_pages", 36, 4, be_int),
                ("schema_cookie", 40, 4, be_int),
                ("schema_format", 44, 4, be_int),
                ("default_cache_size", 48, 4, be_int),
                ("autovacuum_top_root", 52, 4, be_int),
                ("text_encoding", 56, 4, text_encoding),
                ("user_version", 60, 4, be_int),
                ("incremental_vacuum", 64, 4, be_bool),
                ("application_id", 68, 4, be_int),
                ("version_valid_for", 92, 4, be_int),
                ("sqlite_version", 96, 4, be_int),
            ):
                b = header_page[offset : offset + size]
                kw[name] = converter(b)  # type: ignore [operator]
            dbinfo = DatabaseFileInfo(**kw)

        try:
            ok, journal_page = db.read(schema, 1, 0, 32)
        except apsw.SQLError:
            ok = False

        if ok:
            kw: dict[str, Any] = {}  # type: ignore [no-redef]
            if db.pragma("journal_mode") == "wal":
                kw["filename"] = db.filename_wal
                for name, offset, size, converter in (
                    ("magic_number", 0, 4, be_int),
                    ("format_version", 4, 4, be_int),
                    ("page_size", 8, 4, be_page_size),
                    ("checkpoint_sequence_number", 12, 4, be_int),
                    ("salt_1", 16, 4, be_int),
                    ("salt_2", 20, 4, be_int),
                    ("checksum_1", 24, 4, be_int),
                    ("checksum_2", 28, 4, be_int),
                ):
                    b = journal_page[offset : offset + size]
                    kw[name] = converter(b)  # type: ignore [operator]
                journalinfo = WALFileInfo(**kw)
            else:
                header_valid = lambda b: b == b"\xd9\xd5\x05\xf9\x20\xa1\x63\xd7"
                kw["filename"] = db.filename_journal
                for name, offset, size, converter in (
                    ("header", 0, 8, bytes),
                    ("header_valid", 0, 8, header_valid),
                    ("page_count", 8, 4, be_sint),
                    ("random_nonce", 12, 4, be_int),
                    ("initial_pages", 16, 4, be_int),
                    ("sector_size", 20, 4, be_int),
                    ("page_size", 24, 4, be_int),
                ):
                    b = journal_page[offset : offset + size]
                    kw[name] = converter(b)  # type: ignore [operator]
                journalinfo = JournalFileInfo(**kw)

        return dbinfo, journalinfo

    class Trace:
        """Use as a context manager to show each SQL statement run inside the block

        Statements from your code as well as from other parts of SQLite are shown.::

            with apsw.ext.Trace(sys.stdout, db):
                method()
                db.execute("SQL")
                etc

        :param file: File to print to.  If `None` then no information is
               gathered or printed
        :param db: :class:`~apsw.Connection` to trace.
        :param trigger: The names of triggers being executed is always
               shown.  If this is `True` then each statement of an
               executing trigger is shown too.
        :param vtable: If `True` then statements executed behind the
               scenes by virtual tables are shown.
        :param truncate: Truncates SQL text to this many characters
        :param indent: Printed before each line of output

        You are shown each regular statement start with a prefix of ``>``,
        end with a prefix of ``<`` if there were in between statements
        like triggers, ``T`` indicating trigger statements, and ``V``
        indicating virtual table statements.  As each statement ends you
        are shown summary information.

        .. list-table::
            :header-rows: 1
            :widths: auto

            * - Example
              - Description
            * - Time: 1.235
              - Elapsed time since the statement started executing in seconds.
                This is always shown.
            * - Rows: 5
              - How many times SQLite stopped execution providing a row to
                be processed
            * - Changes: 77
              - The difference in the `total change count
                <https://sqlite.org/c3ref/total_changes.html>`__ between
                when the statement started and when it ended.  It will
                include changes made by triggers, virtual table code etc.
            * - FullScanRows: 12,334
              - Number of rows visited doing a full scan of a table.  This
                indicates an opportunity for an index.
            * - Sort: 5
              - The number of times SQLite had to do a sorting operation.
                If you have indexes in the desired order then the sorting
                can be skipped.
            * - AutoIndexRows: 55,988
              - SQLite had to create and add this many rows to an
                `automatic index
                <https://sqlite.org/optoverview.html#automatic_query_time_indexes>`__.
                This indicates an opportunity for an index.
            * - VmStep: 55,102
              - How many `internal steps
                <https://sqlite.org/opcode.html>`__ were needed.
            * - Mem: 84.3KB
              - How much memory was used to hold the statement and working data.

        Tracing is done with :meth:`~apsw.Connection.trace_v2`.

        See :func:`ShowResourceUsage` to get summary information about a
        block as a whole.  You can use this and that at the same time.

        See the :ref:`example <example_Trace>`.
        """

        @dataclasses.dataclass
        class stmt:
            """Tracks a sqlite3_stmt for one statement lifetime

            :meta private:
            """

            sql: str | None = None
            rows: int = 0
            vtable: bool = False
            change_count: int = -1

        def __init__(
            self,
            file: TextIO | None,
            db: apsw.Connection,
            *,
            trigger: bool = False,
            vtable: bool = False,
            truncate: int = 75,
            indent: str = "",
        ):
            self.file = file
            self.db = db
            self.trigger = trigger
            self.vtable = vtable
            self.indent = indent
            self.truncate = truncate

        def _truncate(self, text: str) -> str:
            text = text.strip()
            return text[: self.truncate] + "..." if len(text) > self.truncate else text

        def __enter__(self):
            if not self.file:
                return self

            self.statements: collections.defaultdict[int, Trace.stmt] = collections.defaultdict(Trace.stmt)

            # id,sql of the last SQLITE_TRACE_STMT we output to detect
            # interleaving of queries
            self.last_emitted = None

            self.db.trace_v2(
                apsw.SQLITE_TRACE_STMT | apsw.SQLITE_TRACE_ROW | apsw.SQLITE_TRACE_PROFILE, self._sqlite_trace, id=self
            )

            return self

        def _sqlite_trace(self, event: dict):
            if event["code"] == apsw.SQLITE_TRACE_STMT:
                stmt = self.statements[event["id"]]
                if stmt.change_count == -1:
                    stmt.change_count = event["total_changes"]

                if event["trigger"]:
                    if stmt.sql is None:
                        # its really virtual table
                        stmt.vtable = True
                        stmt.sql = event["sql"]
                        if self.vtable:
                            print(self.indent, "V", self._truncate(event["sql"]), file=self.file)
                            self.last_emitted = event["id"], event["sql"]

                    else:
                        if self.trigger or event["sql"].startswith("TRIGGER "):
                            print(self.indent, "T", self._truncate(event["sql"]), file=self.file)
                            self.last_emitted = event["id"], event["sql"]
                else:
                    assert stmt.sql is None
                    stmt.sql = event["sql"]
                    print(self.indent, ">", self._truncate(event["sql"]), file=self.file)
                    self.last_emitted = event["id"], event["sql"]

            elif event["code"] == apsw.SQLITE_TRACE_ROW:
                self.statements[event["id"]].rows += 1

            elif event["code"] == apsw.SQLITE_TRACE_PROFILE:
                stmt = self.statements.get(event["id"], None)
                if stmt is None:
                    return

                is_trigger = stmt.sql != event["sql"]

                if is_trigger and not self.trigger:
                    return

                interleaving = self.last_emitted != (event["id"], event["sql"])

                if not is_trigger:
                    self.statements.pop(event["id"])

                if stmt.vtable and not self.vtable:
                    return

                if interleaving:
                    print(self.indent, "<" if not stmt.vtable else "V", self._truncate(event["sql"]), file=self.file)

                seconds = event["nanoseconds"] / 1_000_000_000

                fields = [f"Time: {seconds:.03f}"]

                if stmt.rows:
                    fields.append(f"Rows: {stmt.rows:,}")

                changes = event["total_changes"] - stmt.change_count if stmt.change_count != -1 else 0
                if changes:
                    fields.append(f"Changes: {changes:,}")

                for field, desc, threshold in (
                    ("SQLITE_STMTSTATUS_FULLSCAN_STEP", "FullScanRows", 1000),
                    ("SQLITE_STMTSTATUS_SORT", "Sort", 1),
                    ("SQLITE_STMTSTATUS_AUTOINDEX", "AutoIndexRows", 100),
                    ("SQLITE_STMTSTATUS_VM_STEP", "VmStep", 100),
                    ("SQLITE_STMTSTATUS_MEMUSED", "Mem", 16384),
                ):
                    val = event["stmt_status"][field]
                    if val >= threshold:
                        if field == "SQLITE_STMTSTATUS_MEMUSED":
                            power = math.floor(math.log(val, 1024))
                            suffix = ["B", "KB", "MB", "GB", "TB"][int(power)]
                            val = val / 1024**power
                            fields.append(f"{desc}: {val:.1f}{suffix}")
                        else:
                            fields.append(f"{desc}: {val:,}")

                print(
                    self.indent,
                    "   ",
                    "  ".join(fields),
                    file=self.file,
                )

                self.last_emitted = event["id"], event["sql"]

        def __exit__(self, *_):
            self.db.trace_v2(0, None, id=self)

    class ShowResourceUsage:
        """Use as a context manager to show a summary of time, resource, and SQLite usage inside
        the block::

            with apsw.ext.ShowResourceUsage(sys.stdout, db=connection, scope="thread"):
                # do things with the database
                connection.execute("...")
                # and other calculations
                do_work()

        When then context finishes a report is printed to the file.  Only
        non-zero fields are shown - eg if no I/O is done then no I/O
        fields are shown.  See the :ref:`example <example_ShowResourceUsage>`.

        :param file: File to print to.  If `None` then no information is gathered or
               printed
        :param db: :class:`~apsw.Connection` to gather SQLite stats from if not `None`.
               Statistics from each SQL statement executed are added together.
        :param scope: Get :data:`thread <resource.RUSAGE_THREAD>` or
               :data:`process <resource.RUSAGE_SELF>` stats, or `None`.
               Note that MacOS only supports process, and Windows doesn't support
               either.
        :param indent: Printed before each line of output

        Timing information comes from :func:`time.monotonic` and :func:`time.process_time`,
        resource usage from :func:`resource.getrusage` (empty for Windows), and SQLite from
        :meth:`~apsw.Connection.trace_v2`.

        See :func:`Trace` to trace individual statements.  You can use
        this and that at the same time.

        See the :ref:`example <example_ShowResourceUsage>`.
        """

        def __init__(
            self,
            file: TextIO | None,
            *,
            db: apsw.Connection | None = None,
            scope: Literal["thread"] | Literal["process"] | None = None,
            indent: str = "",
        ):
            self.file = file
            self.db = db
            self.indent = indent
            if scope not in {"thread", "process", None}:
                raise ValueError(f"scope { scope } not a valid choice")
            self.scope = file and self._get_resource and scope

        try:
            import resource

            _get_resource = resource.getrusage
            _get_resource_param = {
                "thread": getattr("resource", "RUSAGE_THREAD", resource.RUSAGE_SELF),
                "process": resource.RUSAGE_SELF,
            }

            del resource

        except ImportError:
            _get_resource = None

        def __enter__(self):
            if not self.file:
                return self
            self._times = time.process_time(), time.monotonic()
            if self.scope:
                self._usage = self._get_resource(self._get_resource_param[self.scope])
            if self.db:
                self.db.trace_v2(apsw.SQLITE_TRACE_PROFILE, self._sqlite_trace, id=self)
                self.stmt_status = {}
                self.db_status = self.db_status_get()
            return self

        def _sqlite_trace(self, v):
            for k, val in v["stmt_status"].items():
                self.stmt_status[k] = val + self.stmt_status.get(k, 0)

        def db_status_get(self) -> dict[str, int]:
            ":meta private:"
            return {
                "SQLITE_DBSTATUS_LOOKASIDE_USED": self.db.status(apsw.SQLITE_DBSTATUS_LOOKASIDE_USED)[0],
                "SQLITE_DBSTATUS_LOOKASIDE_HIT": self.db.status(apsw.SQLITE_DBSTATUS_LOOKASIDE_HIT)[1],
                "SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE": self.db.status(apsw.SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE)[1],
                "SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL": self.db.status(apsw.SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL)[1],
                "SQLITE_DBSTATUS_CACHE_USED": self.db.status(apsw.SQLITE_DBSTATUS_CACHE_USED)[0],
                "SQLITE_DBSTATUS_SCHEMA_USED": self.db.status(apsw.SQLITE_DBSTATUS_SCHEMA_USED)[0],
                "SQLITE_DBSTATUS_STMT_USED": self.db.status(apsw.SQLITE_DBSTATUS_STMT_USED)[0],
                "SQLITE_DBSTATUS_CACHE_HIT": self.db.status(apsw.SQLITE_DBSTATUS_CACHE_HIT)[0],
                "SQLITE_DBSTATUS_CACHE_MISS": self.db.status(apsw.SQLITE_DBSTATUS_CACHE_MISS)[0],
                "SQLITE_DBSTATUS_CACHE_WRITE": self.db.status(apsw.SQLITE_DBSTATUS_CACHE_WRITE)[0],
                "SQLITE_DBSTATUS_CACHE_SPILL": self.db.status(apsw.SQLITE_DBSTATUS_CACHE_SPILL)[0],
                "SQLITE_DBSTATUS_DEFERRED_FKS": self.db.status(apsw.SQLITE_DBSTATUS_DEFERRED_FKS)[0],
            }

        def __exit__(self, *_) -> None:
            if not self.file:
                return

            vals: list[tuple[str, int | float]] = []

            times = time.process_time(), time.monotonic()
            if times[0] - self._times[0] >= 0.001:
                vals.append((self._descriptions["process_time"], times[0] - self._times[0]))
            if times[1] - self._times[1] >= 0.001:
                vals.append((self._descriptions["monotonic"], times[1] - self._times[1]))

            if self.scope:
                usage = self._get_resource(self._get_resource_param[self.scope])

                for k in dir(usage):
                    if not k.startswith("ru_"):
                        continue
                    delta = getattr(usage, k) - getattr(self._usage, k)
                    if delta >= 0.001:
                        vals.append((self._descriptions.get(k, k), delta))

            if self.db:
                self.db.trace_v2(0, None, id=self)
                if self.stmt_status:
                    self.stmt_status.pop("SQLITE_STMTSTATUS_MEMUSED")
                    for k, v in self.stmt_status.items():
                        if v:
                            vals.append((self._descriptions[k], v))
                    for k, v in self.db_status_get().items():
                        diff = v - self.db_status[k]
                        if diff:
                            vals.append((self._descriptions[k], diff))

            if not vals:
                # there was no meaningful change, so output nothing
                pass
            else:
                max_width = max(len(k) for k in self._descriptions.values())
                for k, v in vals:
                    if isinstance(v, float):
                        v = f"{ v:.3f}"
                    else:
                        v = f"{ v:,}"
                    print(self.indent, " " * (max_width - len(k)), k, " ", v, file=self.file, sep="")

        _descriptions = {
            "process_time": "Total CPU consumption",
            "monotonic": "Wall clock",
            "SQLITE_STMTSTATUS_FULLSCAN_STEP": "SQLite full table scan",
            "SQLITE_STMTSTATUS_SORT": "SQLite sort operations",
            "SQLITE_STMTSTATUS_AUTOINDEX": "SQLite auto index rows added",
            "SQLITE_STMTSTATUS_VM_STEP": "SQLite vm operations",
            "SQLITE_STMTSTATUS_REPREPARE": "SQLite statement reprepares",
            "SQLITE_STMTSTATUS_RUN": "SQLite statements completed",
            "SQLITE_STMTSTATUS_FILTER_HIT": "SQLite bloom filter hit",
            "SQLITE_STMTSTATUS_FILTER_MISS": "SQLite bloom filter miss",
            "SQLITE_DBSTATUS_LOOKASIDE_USED": "SQLite lookaside slots used",
            "SQLITE_DBSTATUS_LOOKASIDE_HIT": "SQLite allocations using lookaside",
            "SQLITE_DBSTATUS_LOOKASIDE_MISS_SIZE": "SQLite allocations too big for lookaside",
            "SQLITE_DBSTATUS_LOOKASIDE_MISS_FULL": "SQLite allocations lookaside full",
            "SQLITE_DBSTATUS_CACHE_USED": "SQLite pager memory",
            "SQLITE_DBSTATUS_SCHEMA_USED": "SQLite schema memory",
            "SQLITE_DBSTATUS_STMT_USED": "SQLite statement memory",
            "SQLITE_DBSTATUS_CACHE_HIT": "SQLite pager cache hit",
            "SQLITE_DBSTATUS_CACHE_MISS": "SQLite pager cache miss",
            "SQLITE_DBSTATUS_CACHE_WRITE": "SQLite pager cache writes",
            "SQLITE_DBSTATUS_CACHE_SPILL": "SQLite pager cache writes during transaction",
            "SQLITE_DBSTATUS_DEFERRED_FKS": "SQLite unresolved foreign keys",
            "ru_utime": "Time in user mode",
            "ru_stime": "Time in system mode",
            "ru_maxrss": "Maximum resident set size",
            "ru_ixrss": "Shared memory size",
            "ru_idrss": "Unshared memory size",
            "ru_isrss": "Unshared stack size",
            "ru_minflt": "Page faults - no I/O",
            "ru_majflt": "Page faults with I/O",
            "ru_nswap": "Number of swapouts",
            "ru_inblock": "Block input operations",
            "ru_oublock": "Block output operations",
            "ru_msgsnd": "Messages sent",
            "ru_msgrcv": "Messages received",
            "ru_nsignals": "Signals received",
            "ru_nvcsw": "Voluntary context switches",
            "ru_nivcsw": "Involuntary context switches",
        }

    @dataclasses.dataclass
    class PageUsage:
        """Returned by :func:`analyze_pages`"""

        page_size: int
        "Size of pages in bytes.  All pages in the database are the same size."
        pages_used: int
        "Pages with content"
        sequential_pages: int
        "How many pages were sequential in the database file"
        data_stored: int
        "Bytes of SQL content stored"
        cells: int
        """Cells are what is `stored <https://www.sqlite.org/fileformat.html#b_tree_pages>`__
        including sizing information, pointers to overflow etc"""
        max_payload: int
        "Largest cell size"
        tables: list[str]
        "Names of tables providing these statistics"
        indices: list[str]
        "Names of indices providing these statistics"

    @dataclasses.dataclass
    class DatabasePageUsage(PageUsage):
        """Returned by :func:`analyze_pages` when asking about the database as a whole"""

        pages_total: int
        "Number of pages in the database"
        pages_freelist: int
        "How many pages are unused, for example if data got deleted"
        max_page_count: int
        "Limit on the `number of pages <https://www.sqlite.org/pragma.html#pragma_max_page_count>`__"

    def _analyze_pages_for_name(con: apsw.Connection, schema: str, name: str, usage: PageUsage):
        qschema = '"' + schema.replace('"', '""') + '"'

        for pages_used, ncell, payload, mx_payload in con.execute(
            """SELECT pageno, ncell, payload, mx_payload
                        FROM dbstat(?, 1) WHERE name=?
                    """,
            (schema, name),
        ):
            usage.pages_used += pages_used
            usage.data_stored += payload
            usage.cells += ncell
            usage.max_payload = max(usage.max_payload, mx_payload)
            t = con.execute(f"select type from {qschema}.sqlite_schema where name=?", (name,)).get
            if t == "index":
                usage.indices.append(name)
                usage.indices.sort()
            else:
                usage.tables.append(name)
                usage.tables.sort()

            # by definition the first page is sequential but won't match next, so fake it
            sequential = 1
            next = None
            for (pageno,) in con.execute("select pageno from dbstat(?) WHERE name=? ORDER BY path", (schema, name)):
                sequential += pageno == next
                next = pageno + 1
            usage.sequential_pages += sequential

    def analyze_pages(con: apsw.Connection, scope: int, schema: str = "main") -> DatabasePageUsage | dict[str, PageUsage]:
        """Summarizes page usage for the database

        The `dbstat <https://www.sqlite.org/dbstat.html>`__ virtual table
        is used to gather statistics.

        See `example output <_static/samples/analyze_pages.txt>`__.

        :param con: Connection to use
        :param scope:
            .. list-table::
                :widths: auto
                :header-rows: 1

                * - Value
                  - Scope
                  - Returns
                * - ``0``
                  - The database as a whole
                  - :class:`DatabasePageUsage`
                * - ``1``
                  - Tables and their indices are grouped together.  Virtual tables
                    like FTS5 have multiple backing tables which are grouped.
                  - A :class:`dict` where the key is the name of the
                    table, and a corresponding :class:`PageUsage` as the
                    value.  The :attr:`PageUsage.tables` and
                    :attr:`PageUsage.indices` fields tell you which ones
                    were included.
                * - ``2``
                  - Each table and index separately.
                  - :class:`dict` of each name and a corresponding
                    :class:`PageUsage` where one of the
                    :attr:`PageUsage.tables` and :attr:`PageUsage.indices`
                    fields will have the name.

        .. note::

            dbstat is present in PyPI builds, and many platform SQLite
            distributions.  You can use `pragma module_list
            <https://www.sqlite.org/pragma.html#pragma_module_list>`__ to
            check.  If the table is not present then calling this function
            will give :class:`apsw.SQLError` with message ``no such table:
            dbstat``.
        """

        qschema = '"' + schema.replace('"', '""') + '"'

        if scope == 0:
            total_usage = DatabasePageUsage(
                page_size=con.pragma("page_size", schema=schema),
                pages_total=con.pragma("page_count", schema=schema),
                pages_freelist=con.pragma("freelist_count", schema=schema),
                max_page_count=con.pragma("max_page_count", schema=schema),
                pages_used=0,
                data_stored=0,
                sequential_pages=0,
                tables=[],
                indices=[],
                cells=0,
                max_payload=0,
            )

            _analyze_pages_for_name(con, schema, "sqlite_schema", total_usage)
            for (name,) in con.execute(f"select name from {qschema}.sqlite_schema where rootpage!=0"):
                _analyze_pages_for_name(con, schema, name, total_usage)

            return total_usage

        res = {}

        grouping: dict[str, list[str]] = {}

        if scope == 2:
            grouping["sqlite_schema"] = ["sqlite_schema"]
            for (name,) in con.execute(f"select name from {qschema}.sqlite_schema where rootpage!=0"):
                grouping[name] = [name]
        elif scope == 1:
            grouping["sqlite"] = ["sqlite_schema"]
            is_virtual_table: set[str] = set()
            for type, name, tbl_name, rootpage in con.execute(
                # the order by tbl_name is so we get eg fts base table
                # name before the shadow tables.  type desc is so that 'table'
                # comes before index
                f"""select type, name, tbl_name, rootpage
                    from {qschema}.sqlite_schema
                    where type in ('table', 'index')
                    order by tbl_name, type desc"""
            ):
                if type == "index":
                    # indexes always know their table-
                    grouping[tbl_name].append(name)
                    continue
                if name.startswith("sqlite_"):
                    grouping["sqlite"].append(name)
                    continue
                if rootpage == 0:
                    grouping[name] = []
                    is_virtual_table.add(name)
                    continue
                # shadow table? we assume an underscore separator searching longest names first
                for n in sorted(grouping, key=lambda x: (len(x), x)):
                    if n in is_virtual_table and name.startswith(n + "_"):
                        grouping[n].append(name)
                        break
                else:
                    grouping[name] = [name] if rootpage else []
        else:
            raise ValueError(f"Unknown {scope=}")

        for group, names in sorted(grouping.items()):
            usage = PageUsage(
                page_size=con.pragma("page_size", schema=schema),
                pages_used=0,
                data_stored=0,
                sequential_pages=0,
                tables=[],
                indices=[],
                cells=0,
                max_payload=0,
            )

            for name in names:
                _analyze_pages_for_name(con, schema, name, usage)
            res[group] = usage

        return res

    def storage(v: int) -> str:
        """Converts number to storage size (KB, MB, GB etc)

        :meta private:
        """
        if not v:
            return "0"
        power = math.floor(math.log(v, 1024))
        suffix = ["B", "KB", "MB", "GB", "TB", "PB", "EB"][int(power)]
        if suffix == "B":
            return f"{v}B"
        return f"{v / 1024**power:.1f}".rstrip(".0") + suffix

    def page_usage_to_svg(con: apsw.Connection, out: TextIO, schema: str = "main") -> None:
        """Visualize database space usage as a `SVG <https://en.wikipedia.org/wiki/SVG>`__

        You can hover or click on segments to get more details.  The
        centre circle shows information about the database as a whole, the
        middle ring shows usage grouped by database (combing indices,
        shadow tables for virtual tables), while the outer ring shows each
        index and table separately.

        Uses :func:`analyze_pages` to gather the information.

        :param con: Connection to query
        :param out: Where the svg is written to.  You can use
           :class:`io.StringIO` if you want it as a string.
        :param schema: Which attached database to query

        See `example output <_static/samples/chinook.svg>`__.
        """
        # Angles and distances are used within.  They are in the range 0.0
        # to 1.0 .

        # Coordinates are output as int, so this is the scaling factor
        RADIUS = 1000
        # how much whitespace is outside the circles
        OVERSCAN = 1.05

        def colour_for_angle(angle: float) -> str:
            # we use r g b each offset by a third of the circle
            radians = angle * math.pi
            third = 1 / 3 * math.pi

            red = int(255 * abs(math.cos(radians)))
            green = int(255 * abs(math.cos(third + radians)))
            blue = int(255 * abs(math.cos(third + third + radians)))

            return f"#{red:02x}{green:02x}{blue:02x}"

        def pos_for_angle(angle: float, distance: float) -> tuple[float, float]:
            "give x,y for distance from centre"

            # the minus bit is because trig has east as 0 but we want north as
            # zero
            radians = angle * 2 * math.pi - (1 / 4 * 2 * math.pi)

            return distance * math.cos(radians), distance * math.sin(radians)

        # these two are used in fstrings hence the short names
        def c(v: float | list[float]) -> str:
            # outputs a coordinate scaling by RADIUS
            if isinstance(v, float):
                return str(round(v * RADIUS))
            return " ".join(str(round(x * RADIUS)) for x in v)

        def p(angle: float, distance: float):
            # outputs a coordinate scaling by RADIUS
            return c(pos_for_angle(angle, distance))

        def slice(
            id: str,
            start_angle: float,
            end_angle: float,
            start_distance: float,
            end_distance: float,
            color: str | None = None,
        ):
            # produces one of the circular slices
            large = 1 if (end_angle - start_angle) > 1 / 2 else 0

            d = []
            d.append(f"M {p(start_angle, start_distance)}")
            d.append(f"L {p(start_angle, end_distance)}")
            d.append(f"A {c(end_distance)} {c(end_distance)} 0 {large} 1 {p(end_angle, end_distance)}")
            d.append(f"L {p(end_angle, start_distance)}")
            d.append(f"A {c(start_distance)} {c(start_distance)} 0 {large} 0 {p(start_angle, start_distance)}")

            ds = " ".join(d)

            fill = color or colour_for_angle((start_angle + end_angle) / 2)
            return f"""<a href="#" id="{id}"><path d="{ds}" stroke="black" fill="{fill}" stroke-width="1px"/></a>"""

        def text(pos: tuple[float, float], id: str, name: str, ring: int, usage: DatabasePageUsage | PageUsage) -> str:
            # produces text infobox
            x, y = c(pos[0]), c(pos[1])
            vspace = 'dy="1.1em"'
            e = html.escape
            res: list[str] = []
            res.append(f"""<text id="{id}" x="{x}" y="{y}" class="infobox">""")
            res.append(f"""<tspan x="{x}" dy="-3em" class="name">{e(name)}</tspan>""")
            if ring == -1:
                size = storage((usage.pages_total - usage.pages_used) * usage.page_size)
                res.append(f"""<tspan x="{x}" {vspace}>{size} unused</tspan>""")

            elif ring == 0:
                assert isinstance(usage, apsw.ext.DatabasePageUsage)
                total = storage(usage.pages_total * usage.page_size)
                used = storage(usage.pages_used * usage.page_size)
                page = storage(usage.page_size)
                res.append(f"""<tspan x="{x}" {vspace}>{page} page size</tspan>""")
                res.append(f"""<tspan x="{x}" {vspace}>{used} / {total} used</tspan>""")
                res.append(f"""<tspan x="{x}" {vspace}>{len(usage.tables):,} tables</tspan>""")
                res.append(f"""<tspan x="{x}" {vspace}>{len(usage.indices):,} indices</tspan>""")
            else:
                if ring == 2:
                    kind = "table" if usage.tables else "index"
                    res.append(f"""<tspan x="{x}" {vspace}>({kind})</tspan>""")
                size = storage(usage.pages_used * usage.page_size)
                res.append(f"""<tspan x="{x}" {vspace}>{size}</tspan>""")
                if ring == 1:
                    res.append(f"""<tspan x="{x}" {vspace}>{len(usage.tables):,} tables</tspan>""")
                    res.append(f"""<tspan x="{x}" {vspace}>{len(usage.indices):,} indices</tspan>""")
            if ring >= 0:
                res.append(
                    f"""<tspan x="{x}" {vspace}>{usage.sequential_pages/max(usage.pages_used, 1):.0%} sequential</tspan>"""
                )
                res.append(f"""<tspan x="{x}" {vspace}>{storage(usage.data_stored)} SQL data</tspan>""")
                res.append(f"""<tspan x="{x}" {vspace}>{storage(usage.max_payload)} max payload</tspan>""")
                res.append(f"""<tspan x="{x}" {vspace}>{usage.cells:,} cells</tspan>""")

            res.append("""</text>""")
            return "\n".join(res)

        # check we can get the information
        root, group, each = (apsw.ext.analyze_pages(con, n, schema) for n in range(3))

        if not root.pages_total:
            raise ValueError(f"database {schema=} is empty")

        # maps which element hovering over causes a response on
        hover_response: dict[str, str] = {}

        # z-order is based on output order so texts go last
        texts: list[str] = []

        id_counter = 0

        def next_ids():
            # return pais of element ids used to map slice to corresponding text
            nonlocal id_counter
            PREFIX = "id"
            hover_response[f"{PREFIX}{id_counter}"] = f"{PREFIX}{id_counter + 1}"
            id_counter += 2
            return f"{PREFIX}{id_counter-2}", f"{PREFIX}{id_counter-1}"

        print(
            f"""<svg xmlns="http://www.w3.org/2000/svg" viewBox="-{round(RADIUS*OVERSCAN)} {-round(RADIUS*OVERSCAN)} {round(RADIUS*OVERSCAN*2)} {round(RADIUS*OVERSCAN*2)}">""",
            file=out,
        )

        # inner summary circle
        id, resp = next_ids()
        print(f"""<a href="#" id="{id}"><circle r="{c(.3)}" fill="#777"/></a>""", file=out)
        texts.append(text(pos_for_angle(0, 0), resp, os.path.basename(con.db_filename(schema)) or '""', 0, root))

        # inner ring
        start = Fraction()
        for name, usage in group.items():
            ring1_proportion = Fraction(usage.pages_used, root.pages_total)
            id, resp = next_ids()
            print(slice(id, float(start), float(start + ring1_proportion), 1 / 3, 0.6), file=out)
            texts.append(text(pos_for_angle(float(start + ring1_proportion / 2), (1 / 3 + 0.6) / 2), resp, name, 1, usage))
            ring2_start = start
            start += ring1_proportion

            # corresponding outer ring
            for child in sorted(usage.tables + usage.indices):
                usage2 = each[child]
                ring2_proportion = Fraction(usage2.pages_used, root.pages_total)
                id, resp = next_ids()
                print(slice(id, float(ring2_start), float(ring2_start + ring2_proportion), 2 / 3, 1.0), file=out)
                texts.append(
                    text(pos_for_angle(float(ring2_start + ring2_proportion / 2), (2 / 3 + 1) / 2), resp, child, 2, usage2)
                )
                ring2_start += ring2_proportion

        if root.pages_used < root.pages_total:
            id, resp = next_ids()
            print(slice(id, float(start), 1.0, 1 / 3, 1.0, "#aaa"), file=out)
            texts.append(text(pos_for_angle(float((1 + start) / 2), 0.5), resp, "Free Space", -1, root))

        for t in texts:
            print(t, file=out)

        print(
            """<style>
            .infobox { text-anchor: middle; dominant-baseline: middle; font-size: 28pt;
                fill: black; stroke: white; stroke-width:4pt; paint-order: stroke;
                font-family: ui-sans-serif, sans-serif; }
            tspan {font-weight: 600;}
            .name {font-weight: 900; text-decoration: underline;}
        """,
            file=out,
        )
        for source, target in hover_response.items():
            print(f"""#{target} {{ display: none;}}""", file=out)
            print(
                f"""#{source}:hover ~ #{target}, #{target}:hover, #{source}:active ~ #{target}, #{target}:active
                    {{display:block;}}""",
                file=out,
            )

        print("</style></svg>", file=out)

    query_limit_context: contextvars.ContextVar[query_limit.limit] = contextvars.ContextVar("apsw.ext.query_limit_context")
    """Stores the current query limits

    :meta private:
    """

    class QueryLimitNoException(Exception):
        """Indicates that no exception will be raised when a :class:`query_limit` is exceeded"""

        pass

    class query_limit:
        """Use as a context manager to limit execution time and rows processed in the block

        When the total number of rows processed hits the row limit, or
        timeout seconds have elapsed an exception is raised to exit the
        block.

        .. code-block::

            with query_limit(db, row_limit = 1000, timeout = 2.5):
                db.execute("...")
                for row in db.execute("..."):
                    ,,,
                db.execute("...")

        :param db: Connection to monitor
        :param row_limit: Maximum number of rows to process, across all
            queries.  :class:`None` (default) means no limit
        :param timeout: Maximum elapsed time in seconds.  :class:`None`
            (default) means no limit
        :param row_exception: Class of exception to raise when row limit
            is hit
        :param timeout_exception: Class of exception to raise when timeout
            is hit
        :param timeout_steps: How often the elapsed time is checked in
            SQLite internal operations (see :meth:`~apsw.Connection.set_progress_handler`)

        If the exception is :class:`QueryLimitNoException` (default) then
        no exception is passed on when the block exits.

        Row limits are implemented by :meth:`~apsw.Connection.trace_v2` to
        monitor rows.  Only rows directly in your queries are counted -
        for example rows used by virual tables like FTS5 in the
        background, or triggers are not counted.

        Time limits are implemented by
        :meth:`~apsw.Connection.set_progress_handler` to monitor the
        elapsed :func:`time <time.monotonic>`.  This means the elapsed
        time is only checked while running SQLite queries.

        :meth:`~apsw.Connection.trace_v2` and
        :meth:`~apsw.Connection.set_progress_handler` implement multiple
        registrations so query_limit will not interfere with any you may
        have registered.

        If you use nested query_limit blocks then only the limits set by
        the closest block apply within that block.

        See the :ref:`example <example_query_limit>`
        """

        @dataclasses.dataclass
        class limit:
            """ "Current limit in effect

            :meta private:"""

            rows_remaining: int | None = None
            "How many more rows can be returned"
            time_expiry: float | None = None
            "time.monotic value when we stop"
            statements: dict[int, bool] = dataclasses.field(default_factory=dict)
            """key is statement id, value is if its rows count towards rows remaining"""

        def __init__(
            self,
            db: apsw.Connection,
            *,
            row_limit: int | None = None,
            timeout: float | None = None,
            row_exception: type[Exception] = QueryLimitNoException,
            timeout_exception: type[Exception] = QueryLimitNoException,
            timeout_steps: int = 100,
        ):
            self.db = db
            self.row_limit = row_limit
            self.timeout = timeout
            self.row_exception = row_exception
            self.timeout_exception = timeout_exception
            self.timeout_steps = timeout_steps

        def __enter__(self) -> None:
            "Context manager entry point"

            limit = self.limit()

            if self.row_limit is not None:
                self.db.trace_v2(
                    apsw.SQLITE_TRACE_STMT | apsw.SQLITE_TRACE_ROW | apsw.SQLITE_TRACE_PROFILE, self.trace, id=self
                )
                limit.rows_remaining = self.row_limit

            if self.timeout is not None:
                limit.time_expiry = time.monotonic() + self.timeout
                self.db.set_progress_handler(self.progress, self.timeout_steps, id=self)

            self.context_token = query_limit_context.set(limit)
            self.my_limit = limit
            return None

        def __exit__(self, exc_type, *_):
            "Context manager exit point"

            self.db.trace_v2(0, None, id=self)
            self.db.set_progress_handler(None, id=self)

            limit: query_limit.limit = query_limit_context.get()
            query_limit_context.reset(self.context_token)

            if limit is self.my_limit and exc_type is QueryLimitNoException:
                return True

            # pass on whatever the exception was
            return False

        def trace(self, event: dict):
            """Process statement events to check for row limits

            :meta private:"""
            limit: query_limit.limit = query_limit_context.get()

            if limit is not self.my_limit:
                return

            if event["code"] == apsw.SQLITE_TRACE_PROFILE:
                limit.statements.pop(event["id"], None)

            elif event["code"] == apsw.SQLITE_TRACE_STMT:
                # trigger is True for both triggers and vtables, and we ignore them
                limit.statements[event["id"]] = not event["trigger"]

            elif event["code"] == apsw.SQLITE_TRACE_ROW:
                # we ignore unknown statements
                if limit.statements.get(event["id"], False):
                    limit.rows_remaining -= 1
                    if limit.rows_remaining < 0:
                        raise self.row_exception("query row limit hit")

        def progress(self):
            """Progress handler to check for time expiry

            :meta private:
            """
            limit: query_limit.limit = query_limit_context.get()

            if limit is self.my_limit and time.monotonic() >= limit.time_expiry:
                raise self.timeout_exception("query time limit hit")

            return False

    def format_query_table(
        db: apsw.Connection,
        query: str,
        bindings: apsw.Bindings | None = None,
        *,
        colour: bool = False,
        quote: bool = False,
        string_sanitize: Callable[[str], str] | Literal[0] | Literal[1] | Literal[2] = 0,
        binary: Callable[[bytes], str] = lambda x: f"[ { len(x) } bytes ]",
        null: str = "(null)",
        truncate: int = 4096,
        truncate_val: str = " ...",
        text_width: int = 80,
        use_unicode: bool = True,
    ) -> str:
        r"""Produces query output in an attractive text table

        See :ref:`the example <example_format_query>`.

        :param db: Connection to run the query on
        :param query: Query to run
        :param bindings: Bindings for query (if needed)
        :param colour: If True then `ANSI colours <https://en.wikipedia.org/wiki/ANSI_escape_code#Colors>`__ are
            used to outline the header, and show the type of each value.
        :param quote: If True then :meth:`apsw.format_sql_value` is used to get a textual representation of a
             value
        :param string_sanitize:  If this is a callable then each string is passed to it for cleaning up.
            Bigger numbers give more sanitization to the string.  Using an example source string of::

                '''hello \\ \t\f\0日本語 world'''

            .. list-table::
                :header-rows: 1
                :widths: auto

                * - param
                  - example output
                  - description
                * - 0
                  - hello \\\\  \0日本語 world
                  - Various whitespace (eg tabs, vertical form feed) are replaced. backslashes
                    are escaped, embedded nulls become \\0
                * - 1
                  - hello \\\\  \\0{CJK UNIFIED IDEOGRAPH-65E5}{CJK UNIFIED IDEOGRAPH-672C}{CJK UNIFIED IDEOGRAPH-8A9E} world
                  - After step 0, all non-ascii characters are replaced with their :func:`apsw.unicode.codepoint_name`
                * - 2
                  - hello.\\........world
                  - All non-ascii characters and whitespace are replaced by a dot

        :param binary: Called to convert bytes to string
        :param null: How to represent the null value
        :param truncate: How many characters to truncate long strings at (after sanitization)
        :param truncate_val: Appended to truncated strings to show it was truncated
        :param text_width: Maximum output width to generate
        :param use_unicode: If True then unicode line drawing characters are used.  If False then +---+ and | are
            used.
        """
        # args we pass on to format_table
        kwargs = {
            "colour": colour,
            "quote": quote,
            "string_sanitize": string_sanitize,
            "binary": binary,
            "null": null,
            "truncate": truncate,
            "truncate_val": truncate_val,
            "text_width": text_width,
            "use_unicode": use_unicode,
        }

        res: list[str] = []

        cursor = db.cursor()
        colnames = None
        rows = []

        def trace(c: apsw.Cursor, query: str, bindings: apsw.Bindings | None) -> bool:
            nonlocal colnames, rows
            if colnames:
                res.append(format_query_table._format_table(colnames, rows, **kwargs))
                rows = []
            colnames = [n for n, _ in c.get_description()]
            return True

        cursor.exec_trace = trace
        # mitigate any existing row tracer
        if db.row_trace:
            cursor.row_trace = lambda x, y: y

        for row in cursor.execute(query, bindings):
            rows.append(list(row))

        if colnames:
            res.append(format_query_table._format_table(colnames, rows, **kwargs))  # type: ignore[attr-defined]

        if len(res) == 1:
            return res[0]
        return "\n".join(res)

    def _format_table(
        colnames: list[str],
        rows: list[apsw.SQLiteValues],
        colour: bool,
        quote: bool,
        string_sanitize: Callable[[str], str] | Literal[0] | Literal[1] | Literal[2],
        binary: Callable[[bytes], str],
        null: str,
        truncate: int,
        truncate_val: str,
        text_width: int,
        use_unicode: bool,
    ) -> str:
        "Internal table formatter"
        if colour:
            c: Callable[[int], str] = lambda v: f"\x1b[{ v }m"
            colours = {
                # inverse
                "header_start": c(7) + c(1),
                "header_end": c(27) + c(22),
                # red
                "null_start": c(31),
                "null_end": c(39),
                # yellow
                "string_start": c(33),
                "string_end": c(39),
                # blue
                "blob_start": c(34),
                "blob_end": c(39),
                # magenta
                "number_start": c(35),
                "number_end": c(39),
                # green
                "pyobject_start": c(32),
                "pyobject_end": c(39),
            }

            def colour_wrap(text: str, kind: type | None, header: bool = False) -> str:
                if header:
                    return colours["header_start"] + text + colours["header_end"]
                if kind is str:
                    tkind = "string"
                elif kind is bytes:
                    tkind = "blob"
                elif kind in (int, float):
                    tkind = "number"
                elif kind is NoneType:
                    tkind = "null"
                else:
                    tkind = "pyobject"
                return colours[f"{tkind}_start"] + text + colours[f"{tkind}_end"]

        else:
            colours = {}

            def colour_wrap(text: str, kind: type | None, header: bool = False) -> str:
                return text

        colwidths = [max(len(v) for v in c.splitlines()) for c in colnames]
        coltypes: list[set[type]] = [set() for _ in colnames]

        # type, measure and stringize each cell
        for row in rows:
            for i, cell in enumerate(row):
                coltypes[i].add(type(cell))
                if isinstance(cell, str):
                    if callable(string_sanitize):
                        cell = string_sanitize(cell)
                    else:
                        if string_sanitize in (0, 1):
                            cell = cell.replace("\\", "\\\\")
                            cell = cell.replace("\r\n", "\n")
                            cell = cell.replace("\r", " ")
                            cell = cell.replace("\t", " ")
                            cell = cell.replace("\f", "")
                            cell = cell.replace("\v", "")
                            cell = cell.replace("\0", "\\0")

                        if string_sanitize == 1:

                            def repl(s):
                                if s[0] in string.printable:
                                    return s[0]
                                return "{" + (apsw.unicode.codepoint_name(s[0]) or f"\\x{ord(s[0]):02}") + "}"

                            cell = re.sub(".", repl, cell)

                        if string_sanitize == 2:

                            def repl(s):
                                if s[0] in string.printable and s[0] not in string.whitespace:
                                    return s[0]
                                return "."

                            cell = re.sub(".", repl, cell)
                if quote:
                    if isinstance(cell, (NoneType, str, float, int, bytes)):
                        val = apsw.format_sql_value(cell)
                    else:
                        val = repr(cell)
                else:
                    if isinstance(cell, str):
                        val = cell
                    elif isinstance(cell, (float, int)):
                        val = str(cell)
                    elif isinstance(cell, bytes):
                        val = binary(cell)
                    elif cell is None:
                        val = null
                    else:
                        val = str(cell)
                assert isinstance(val, str), f"expected str not { val!r}"

                # cleanup lines
                lines: list[str] = []
                for line in apsw.unicode.split_lines(val):
                    if apsw.unicode.text_width(line) < 0:
                        line = "".join((c if apsw.unicode.text_width(c) >= 0 else "?") for c in line)
                    lines.append(line)
                val = "\n".join(lines)

                if truncate > 0 and apsw.unicode.grapheme_length(val) > truncate:
                    val = apsw.unicode.grapheme_substr(val, 0, truncate) + truncate_val
                row[i] = (val, type(cell))  # type: ignore[index]
                colwidths[i] = max(
                    colwidths[i], max(apsw.unicode.text_width(line) for line in apsw.unicode.split_lines(val)) if val else 0
                )

        ## work out widths
        # we need a space each side of a cell plus a cell separator hence 3
        # "| cell " and another for the final "|"
        total_width: Callable[[], int] = lambda: sum(w + 3 for w in colwidths) + 1

        # proportionally reduce column widths
        victim = len(colwidths) - 1
        while total_width() > text_width:
            # if all are 1 then we can't go any narrower
            if sum(colwidths) == len(colwidths):
                break

            # this makes wider columns take more of the width blame
            proportions = [w * 1.1 / total_width() for w in colwidths]

            excess = total_width() - text_width

            # start with widest columns first
            for _, i in reversed(sorted((proportions[n], n) for n in range(len(colwidths)))):
                w = colwidths[i]
                w -= int(proportions[i] * excess)
                w = max(1, w)
                colwidths[i] = w
                new_excess = total_width() - text_width
                # narrower than needed?
                if new_excess < 0:
                    colwidths[i] -= new_excess
                    break

            # if still too wide, then punish victim
            if total_width() > text_width:
                if colwidths[victim] > 1:
                    colwidths[victim] -= 1
                victim -= 1
                if victim < 0:
                    victim = len(colwidths) - 1

        # can't fit
        if total_width() > text_width:
            raise ValueError(
                f"Results can't be fit in text width { text_width } even with 1 wide columns - at least { total_width() } width is needed"
            )

        # break headers and cells into lines
        def wrap(text: str, width: int) -> list[str]:
            return list(apsw.unicode.text_wrap(text, width))

        colnames = [wrap(colnames[i], colwidths[i]) for i in range(len(colwidths))]  # type: ignore
        for row in rows:
            for i, (text, t) in enumerate(row):  # type: ignore[misc]
                row[i] = (wrap(text, colwidths[i]), t)  # type: ignore

        ## output
        # are any cells more than one line?
        multiline = False
        for row in rows:
            if multiline:
                break
            if any(len(cell[0]) > 1 for cell in row):
                multiline = True
                break

        out_lines: list[str] = []

        def do_bar(chars: str) -> None:
            line = chars[0]
            for i, w in enumerate(colwidths):
                line += chars[1] * (w + 2)
                if i == len(colwidths) - 1:
                    line += chars[3]
                else:
                    line += chars[2]
            out_lines.append(line)

        def do_row(row, sep: str, *, centre: bool = False, header: bool = False) -> None:
            for n in range(max(len(cell[0]) for cell in row)):
                line = sep
                for i, (cell, t) in enumerate(row):
                    text = cell[n] if n < len(cell) else ""
                    text = " " + text.rstrip() + " "
                    lt = apsw.unicode.text_width(text)
                    extra = " " * max(colwidths[i] + 2 - lt, 0)
                    if centre:
                        lpad = extra[: len(extra) // 2]
                        rpad = extra[len(extra) // 2 :]
                    else:
                        lpad = ""
                        rpad = extra
                    if header:
                        text = colour_wrap(lpad + text + rpad, None, header=True)
                    else:
                        text = lpad + colour_wrap(text, t) + rpad
                    line += text + sep
                out_lines.append(line)

        do_bar("┌─┬┐" if use_unicode else "+-++")
        do_row([(c, None) for c in colnames], "│" if use_unicode else "|", centre=True, header=True)

        # rows
        if rows:
            for row in rows:
                if multiline:
                    do_bar("├─┼┤" if use_unicode else "+-++")
                do_row(row, "│" if use_unicode else "|")

        do_bar("└─┴┘" if use_unicode else "+-++")

        return "\n".join(out_lines) + "\n"

    format_query_table._format_table = _format_table  # type: ignore[attr-defined]
    del _format_table

    class VTColumnAccess(enum.Enum):
        "How the column value is accessed from a row, for :meth:`make_virtual_module`"

        By_Index = enum.auto()
        "By number like with tuples and lists - eg :code:`row[3]`"
        By_Name = enum.auto()
        "By name like with dicts - eg :code:`row['quantity']`"
        By_Attr = enum.auto()
        "By attribute like with :mod:`dataclasses` - eg :code:`row.quantity`"

    def get_column_names(row: Any) -> tuple[Sequence[str], VTColumnAccess]:
        r"""
        Works out column names and access given an example row

        *row* can be an instance of a row, or the class used to make
        one (eg a :mod:`dataclass <dataclasses>`)

        .. list-table::
            :header-rows: 1
            :widths: auto

            * - Type
              - Access
              - Column names From
            * - :external:func:`dataclasses.is_dataclass`
              - :attr:`VTColumnAccess.By_Attr`
              - :func:`dataclasses.fields`
            * - :func:`isinstance <isinstance>`\(:class:`tuple`) and :func:`hasattr <hasattr>`\(:code:`"_fields"`) - eg :func:`~collections.namedtuple`
              - :attr:`VTColumnAccess.By_Index`
              - :code:`row._fields`
            * - :func:`hasattr <hasattr>`\(:code:`"__match_args__"`)
              - :attr:`VTColumnAccess.By_Attr`
              - :code:`row.__match_args__` (if not empty)
            * - :func:`isinstance <isinstance>`\(:class:`dict`)
              - :attr:`VTColumnAccess.By_Name`
              - :meth:`dict.keys`
            * - :func:`isinstance <isinstance>`\(:class:`tuple`\)
              - :attr:`VTColumnAccess.By_Index`
              - :code:`columnX` where *X* is zero up to :func:`len <len>`\(:code:`row`)

        Example usage:

        .. code-block::

            def method(arg1, arg2):
                yield {"fruit": "orange", "price": 17, "quantity": 2}

            example_row = next(method(0, 10))
            method.columns, method.column_access = apsw.ext.get_column_names(example_row)

        """
        if is_dataclass(row):
            return tuple(field.name for field in dataclasses.fields(row)), VTColumnAccess.By_Attr
        if isinstance(row, tuple) and hasattr(row, "_fields"):
            return row._fields, VTColumnAccess.By_Index
        if getattr(row, "__match_args__", None):
            return row.__match_args__, VTColumnAccess.By_Attr
        if isinstance(row, dict):
            return tuple(row.keys()), VTColumnAccess.By_Name
        if isinstance(row, tuple):
            return tuple(f"column{ x }" for x in range(len(row))), VTColumnAccess.By_Index
        raise TypeError(f"Can't figure out columns for { row }")

    def make_virtual_module(
        db: apsw.Connection,
        name: str,
        callable: Callable,
        *,
        eponymous: bool = True,
        eponymous_only: bool = False,
        repr_invalid: bool = False,
    ) -> None:
        """
        Registers a read-only virtual table module with *db* based on
        *callable*.  The *callable* must have an attribute named *columns*
        with a list of column names, and an attribute named *column_access*
        with a :class:`VTColumnAccess` saying how to access columns from a row.
        See :meth:`get_column_names` for easily figuring that out.

        The goal is to make it very easy to turn a Python function into a
        virtual table.  For example the following Python function::

          def gendata(start_id, end_id=1000, include_system=False):
              yield (10, "2020-10-21", "readme.txt)
              yield (11, "2019-05-12", "john.txt)

          gendata.columns = ("user_id", "start_date", "file_name")
          gendata.column_access = VTColumnAccess.By_Index

        Will generate a table declared like this, using `HIDDEN
        <https://sqlite.org/vtab.html#hidden_columns_in_virtual_tables>`__
        for parameters:

        .. code-block:: sql

            CREATE TABLE table_name(user_id,
                                    start_date,
                                    file_name,
                                    start_id HIDDEN,
                                    end_id HIDDEN,
                                    include_system HIDDEN);

        :func:`inspect.signature` is used to discover parameter names.

        Positional parameters to *callable* come from the table definition.

        .. code-block:: sql

          SELECT * from table_name(1, 100, 1);

        Keyword arguments come from WHERE clauses.

        .. code-block:: sql

          SELECT * from table_name(1) WHERE
                include_system=1;

        :func:`iter` is called on *callable* with each iteration expected
        to return the next row.  That means *callable* can return its data
        all at once (eg a list of rows), or *yield* them one row at a
        time.  The number of columns must always be the same, no matter
        what the parameter values.

        :param eponymous: Lets you use the *name* as a table name without
                 having to create a virtual table
        :param eponymous_only: Can only reference as a table name
        :param repr_invalid: If *True* then values that are not valid
           :class:`apsw.SQLiteValue` will be converted to a string using
           :func:`repr`

        See the :ref:`example <example_virtual_tables>`

        Advanced
        ++++++++

        The *callable* may also have an attribute named *primary_key*.
        By default the :func:`id` of each row is used as the primary key.
        If present then it must be a column number to use as the primary
        key.  The contents of that column must be unique for every row.

        If you specify a parameter to the table and in WHERE, or have
        non-equality for WHERE clauses of parameters then the query will
        fail with :class:`apsw.SQLError` and a message from SQLite of
        "no query solution"
        """

        class Module:
            def __init__(
                self,
                callable: Callable,
                columns: tuple[str],
                column_access: VTColumnAccess,
                primary_key: int | None,
                repr_invalid: bool,
            ):
                self.columns = columns
                self.callable: Callable = callable
                if not isinstance(column_access, VTColumnAccess):
                    raise ValueError(f"Expected column_access to be { VTColumnAccess } not {column_access!r}")
                self.column_access = column_access
                self.parameters: list[str] = []
                # These are as representable as SQLiteValue and are not used
                # for the actual call.
                self.defaults: list[apsw.SQLiteValue] = []
                for p, v in inspect.signature(callable).parameters.items():
                    self.parameters.append(p)
                    default = None if v.default is inspect.Parameter.empty else v.default
                    try:
                        apsw.format_sql_value(default)
                    except TypeError:
                        default = repr(default)
                    self.defaults.append(default)

                both = set(self.columns) & set(self.parameters)
                if both:
                    raise ValueError(f"Same name in columns and in paramters: { both }")

                self.all_columns: tuple[str] = tuple(self.columns) + tuple(self.parameters)  # type: ignore[assignment]
                self.primary_key = primary_key
                if self.primary_key is not None and not (0 <= self.primary_key < len(self.columns)):
                    raise ValueError(f"{self.primary_key!r} should be None or a column number < { len(self.columns) }")
                self.repr_invalid = repr_invalid
                column_defs = ""
                for i, c in enumerate(self.columns):
                    if column_defs:
                        column_defs += ", "
                    column_defs += f"[{ c }]"
                    if self.primary_key == i:
                        column_defs += " PRIMARY KEY"
                for p in self.parameters:
                    column_defs += f",[{ p }] HIDDEN"

                self.schema = f"CREATE TABLE ignored({ column_defs })"
                if self.primary_key is not None:
                    self.schema += " WITHOUT rowid"

            def Create(self, db, modulename, dbname, tablename, *args: apsw.SQLiteValue) -> tuple[str, apsw.VTTable]:
                if len(args) > len(self.parameters):
                    raise ValueError(f"Too many parameters: parameters accepted are { ' '.join(self.parameters) }")

                param_values = dict(zip(self.parameters, args))

                return self.schema, self.Table(self, param_values)  # type: ignore[return-value]

            Connect = Create

            class Table:
                def __init__(self, module: Module, param_values: dict[str, apsw.SQLiteValue]):
                    self.module = module
                    self.param_values = param_values

                def BestIndexObject(self, o: apsw.IndexInfo) -> bool:
                    idx_str: list[str] = []
                    param_start = len(self.module.columns)
                    for c in range(o.nConstraint):
                        if o.get_aConstraint_iColumn(c) >= param_start:
                            if not o.get_aConstraint_usable(c):
                                continue
                            if o.get_aConstraint_op(c) != apsw.SQLITE_INDEX_CONSTRAINT_EQ:
                                return False
                            o.set_aConstraintUsage_argvIndex(c, len(idx_str) + 1)
                            o.set_aConstraintUsage_omit(c, True)
                            n = self.module.all_columns[o.get_aConstraint_iColumn(c)]
                            # a parameter could be a function parameter and where
                            #    generate_series(7) where start=8
                            # the order they appear in IndexInfo is random so we
                            # have to abort the query because a random one would
                            # prevail
                            if n in idx_str:
                                return False
                            idx_str.append(n)

                    o.idxStr = ",".join(idx_str)
                    # say there are a huge number of rows so the query planner avoids us
                    o.estimatedRows = 2147483647
                    return True

                def Open(self) -> Module.Cursor:
                    return self.module.Cursor(self.module, self.param_values)

                def Disconnect(self) -> None:
                    pass

                Destroy = Disconnect

            class Cursor:
                def __init__(self, module: Module, param_values: dict[str, apsw.SQLiteValue]):
                    self.module = module
                    self.param_values = param_values
                    self.iterating: Iterator[apsw.SQLiteValues] | None = None
                    self.current_row: Any = None
                    self.columns = module.columns
                    self.repr_invalid = module.repr_invalid
                    self.num_columns = len(self.columns)
                    self.access = self.module.column_access
                    col_func = f"_Column_{ self.access.name }"
                    f = getattr(self, col_func, self.Column)
                    if self.repr_invalid:
                        setattr(self, "Column", self._Column_repr_invalid)
                        setattr(self, "_Column_get", f)
                    else:
                        setattr(self, "Column", f)

                def Filter(self, idx_num: int, idx_str: str, args: tuple[apsw.SQLiteValue]) -> None:
                    params: dict[str, apsw.SQLiteValue] = self.param_values.copy()
                    params.update(zip(idx_str.split(","), args))
                    self.iterating = iter(self.module.callable(**params))
                    # proactively advance so we can tell if eof
                    self.Next()

                    self.hidden_values: list[apsw.SQLiteValue] = self.module.defaults[:]
                    for k, v in params.items():
                        self.hidden_values[self.module.parameters.index(k)] = v

                def Eof(self) -> bool:
                    return self.iterating is None

                def Close(self) -> None:
                    if self.iterating:
                        if hasattr(self.iterating, "close"):
                            self.iterating.close()
                        self.iterating = None

                def Column(self, which: int) -> apsw.SQLiteValue:
                    # This is the specification/documentation for the custom
                    # versions which should produce exactly the same output
                    if which >= self.num_columns:
                        return self.hidden_values[which - self.num_columns]
                    if self.access is VTColumnAccess.By_Index:
                        v = self.current_row[which]
                    elif self.access is VTColumnAccess.By_Name:
                        v = self.current_row[self.columns[which]]
                    elif self.access is VTColumnAccess.By_Attr:
                        v = getattr(self.current_row, self.columns[which])
                    if self.repr_invalid and v is not None and not isinstance(v, (int, float, str, bytes)):
                        v = repr(v)
                    return v  # type: ignore[no-any-return]

                def _Column_repr_invalid(self, which: int) -> apsw.SQLiteValue:
                    v = self._Column_get(which)  # type: ignore[attr-defined]
                    return v if v is None or isinstance(v, (int, float, str, bytes)) else repr(v)

                def _Column_By_Attr(self, which: int) -> apsw.SQLiteValue:
                    return (
                        getattr(self.current_row, self.columns[which])
                        if which < self.num_columns
                        else self.hidden_values[which - self.num_columns]
                    )

                def _Column_By_Name(self, which: int) -> apsw.SQLiteValue:
                    return (
                        self.current_row[self.columns[which]]
                        if which < self.num_columns
                        else self.hidden_values[which - self.num_columns]
                    )

                def _Column_By_Index(self, which: int) -> apsw.SQLiteValue:
                    return (
                        self.current_row[which]
                        if which < self.num_columns
                        else self.hidden_values[which - self.num_columns]
                    )

                def Next(self) -> None:
                    try:
                        self.current_row = next(self.iterating)  # type: ignore[arg-type]
                    except StopIteration:
                        if hasattr(self.iterating, "close"):
                            self.iterating.close()  # type: ignore[union-attr]
                        self.iterating = None

                def Rowid(self):
                    if self.module.primary_key is None:
                        return id(self.current_row)
                    return self.Column(self.module.primary_key)

        mod = Module(
            callable,
            callable.columns,  # type: ignore[attr-defined]
            callable.column_access,  # type: ignore[attr-defined]
            getattr(callable, "primary_key", None),
            repr_invalid,
        )

        # unregister any existing first
        db.create_module(name, None)
        db.create_module(
            name,
            mod,  # type: ignore[arg-type]
            use_bestindex_object=True,
            eponymous=eponymous,
            eponymous_only=eponymous_only,
            read_only=True,
        )

    def generate_series_sqlite(start=None, stop=0xFFFFFFFF, step=1):
        """Behaves like SQLite's `generate_series <https://sqlite.org/series.html>`__

        Only integers are supported.  If *step* is negative
        then values are generated from *stop* to *start*

        To use::

            apsw.ext.make_virtual_module(db,
                                         "generate_series",
                                         apsw.ext.generate_series_sqlite)

            db.execute("SELECT value FROM generate_series(1, 10))

        .. seealso::

            :meth:`generate_series`

        """
        if start is None:
            raise ValueError("You must specify a value for start")
        istart = int(start)
        istop = int(stop)
        istep = int(step)
        if istart != start or istop != stop or istep != step:
            raise TypeError("generate_series_sqlite only works with integers")
        if step == 0:
            step = 1
        if step > 0:
            while start <= stop:
                yield (start,)
                start += step
        elif step < 0:
            while stop >= start:
                yield (stop,)
                stop += step

    generate_series_sqlite.columns = ("value",)  # type: ignore[attr-defined]
    generate_series_sqlite.column_access = VTColumnAccess.By_Index  # type: ignore[attr-defined]
    generate_series_sqlite.primary_key = 0  # type: ignore[attr-defined]

    def generate_series(start, stop, step=None):
        """Behaves like Postgres and SQL Server

        `Postgres doc
        <https://www.postgresql.org/docs/current/functions-srf.html>`__
        `SQL server doc
        <https://learn.microsoft.com/en-us/sql/t-sql/functions/generate-series-transact-sql>`__

        Operates on floating point as well as integer.  If step is not
        specified then it is 1 if *stop* is greater than *start* and -1 if
        *stop* is less than *start*.

        To use::

            apsw.ext.make_virtual_module(db,
                                         "generate_series",
                                         apsw.ext.generate_series)

            db.execute("SELECT value FROM generate_series(1, 10))

        .. seealso::

            :meth:`generate_series`

        """
        if step is None:
            if stop > start:
                step = 1
            else:
                step = -1

        if step > 0:
            while start <= stop:
                yield (start,)
                start += step
        elif step < 0:
            while start >= stop:
                yield (start,)
                start += step
        else:
            raise ValueError("step of zero is not valid")

    generate_series.columns = ("value",)  # type: ignore[attr-defined]
    generate_series.column_access = VTColumnAccess.By_Index  # type: ignore[attr-defined]
    generate_series.primary_key = 0  # type: ignore[attr-defined]

    def query_info(
        db: apsw.Connection,
        query: str,
        bindings: apsw.Bindings | None = None,
        *,
        prepare_flags: int = 0,
        actions: bool = False,
        expanded_sql: bool = False,
        explain: bool = False,
        explain_query_plan: bool = False,
    ) -> QueryDetails:
        """Returns information about the query, without running it.

        `bindings` can be `None` if you want to find out what the bindings
        for the query are.

        Set the various parameters to `True` if you also want the
        actions, expanded_sql, explain, query_plan etc filled in.
        """
        res: dict[str, Any] = {"actions": None, "query_plan": None, "explain": None}

        # what we use in queries
        query_bindings = bindings if bindings is not None else apsw._null_bindings

        def tracer(cursor: apsw.Cursor, first_query: str, bindings: apsw.Bindings | None):
            nonlocal res
            res.update(
                {
                    "first_query": first_query,
                    "query": query,
                    "bindings": bindings,
                    "bindings_count": cursor.bindings_count,
                    "bindings_names": cursor.bindings_names,
                    "is_explain": cursor.is_explain,
                    "is_readonly": cursor.is_readonly,
                    "has_vdbe": cursor.has_vdbe,
                    "description": cursor.get_description(),
                    "description_full": None,
                }
            )
            if hasattr(cursor, "description_full"):
                res["description_full"] = cursor.description_full

            assert query == first_query or query.startswith(first_query)
            res["query_remaining"] = query[len(first_query) :] if len(query) > len(first_query) else None
            res["expanded_sql"] = cursor.expanded_sql if expanded_sql else None
            return False

        actions_taken = []

        def auther(code, third, fourth, dbname, trigview):
            a = {"action": code, "action_name": apsw.mapping_authorizer_function[code]}
            if dbname:
                a["database_name"] = dbname
            if trigview:
                a["trigger_or_view"] = trigview

            # this block corresponds to the table at https://sqlite.org/c3ref/c_alter_table.html
            for op, thirdname, fourthname in (
                (apsw.SQLITE_CREATE_INDEX, "index_name", "table_name"),
                (apsw.SQLITE_CREATE_TABLE, "table_name", None),
                (apsw.SQLITE_CREATE_TEMP_INDEX, "index_name", "table_name"),
                (apsw.SQLITE_CREATE_TEMP_TABLE, "table_name", None),
                (apsw.SQLITE_CREATE_TEMP_TRIGGER, "trigger_name", "table_name"),
                (apsw.SQLITE_CREATE_TEMP_VIEW, "view_name", None),
                (apsw.SQLITE_CREATE_TRIGGER, "trigger_name", "table_name"),
                (apsw.SQLITE_CREATE_VIEW, "view_name", None),
                (apsw.SQLITE_DELETE, "table_name", None),
                (apsw.SQLITE_DROP_INDEX, "index_name", "table_name"),
                (apsw.SQLITE_DROP_TABLE, "table_name", None),
                (apsw.SQLITE_DROP_TEMP_INDEX, "index_name", "table_name"),
                (apsw.SQLITE_DROP_TEMP_TABLE, "table_name", None),
                (apsw.SQLITE_DROP_TEMP_TRIGGER, "trigger_name", "table_name"),
                (apsw.SQLITE_DROP_TEMP_VIEW, "view_name", None),
                (apsw.SQLITE_DROP_TRIGGER, "trigger_name", "table_name"),
                (apsw.SQLITE_DROP_VIEW, "view_name", None),
                (apsw.SQLITE_INSERT, "table_name", None),
                (apsw.SQLITE_PRAGMA, "pragma_name", "pragma_value"),
                (apsw.SQLITE_READ, "table_name", "column_name"),
                (apsw.SQLITE_SELECT, None, None),
                (apsw.SQLITE_TRANSACTION, "operation", None),
                (apsw.SQLITE_UPDATE, "table_name", "column_name"),
                (apsw.SQLITE_ATTACH, "file_name", None),
                (apsw.SQLITE_DETACH, "database_name", None),
                (apsw.SQLITE_ALTER_TABLE, "database_name", "table_name"),
                (apsw.SQLITE_REINDEX, "index_name", None),
                (apsw.SQLITE_ANALYZE, "table_name", None),
                (apsw.SQLITE_CREATE_VTABLE, "table_name", "module_name"),
                (apsw.SQLITE_DROP_VTABLE, "table_name", "module_name"),
                (apsw.SQLITE_FUNCTION, None, "function_name"),
                (apsw.SQLITE_SAVEPOINT, "operation", None),
                (apsw.SQLITE_RECURSIVE, None, None),
            ):
                if code == op:
                    if thirdname is not None:
                        a[thirdname] = third
                    if fourthname is not None:
                        a[fourthname] = fourth
                    break
            else:
                raise ValueError(f"Unknown authorizer code { code }")
            actions_taken.append(QueryAction(**a))
            return apsw.SQLITE_OK

        cur = db.cursor()
        cur.exec_trace = tracer
        if actions:
            orig_authorizer = db.authorizer
            db.authorizer = auther
        try:
            cur.execute(
                query,
                query_bindings,
                can_cache=False,
                prepare_flags=prepare_flags,
            )
        except apsw.ExecTraceAbort:
            pass
        finally:
            if actions:
                db.authorizer = orig_authorizer
        cur.exec_trace = None
        if actions:
            res["actions"] = actions_taken

        if explain and not res["is_explain"]:
            vdbe: list[VDBEInstruction] = []
            for row in cur.execute(res["first_query"], query_bindings, explain=1):
                vdbe.append(
                    VDBEInstruction(**dict((v[0][0], v[1]) for v in zip(cur.get_description(), row) if v[1] is not None))
                )
            res["explain"] = vdbe

        if explain_query_plan and not res["is_explain"]:
            subn = "sub"
            byid: Any = {0: {"detail": "QUERY PLAN"}}

            for row in cur.execute(res["first_query"], query_bindings, explain=2):
                node = dict((v[0][0], v[1]) for v in zip(cur.get_description(), row) if v[0][0] != "notused")
                assert len(node) == 3  # catch changes in returned format
                parent: list[str | dict[str, Any]] = byid[node["parent"]]
                if subn not in parent:
                    parent[subn] = [node]  # type: ignore[call-overload]
                else:
                    parent[subn].append(node)  # type: ignore[call-overload]
                byid[node["id"]] = node

            def flatten(node: Any) -> dict[str, Any]:
                res = {"detail": node["detail"]}
                if subn in node:
                    res[subn] = [QueryPlan(**flatten(child)) for child in node[subn]]
                return res

            res["query_plan"] = QueryPlan(**flatten(byid[0]))

        return QueryDetails(**res)

    @dataclass
    class QueryDetails:
        "A :mod:`dataclass <dataclasses>` that provides detailed information about a query, returned by :func:`query_info`"

        query: str
        "Original query provided"
        bindings: apsw.Bindings | None
        "Bindings provided"
        first_query: str
        "The first statement present in query"
        query_remaining: str | None
        "Query text after the first one if multiple were in query, else None"
        is_explain: int
        ":attr:`Cursor.is_explain <apsw.Cursor.is_explain>`"
        is_readonly: bool
        ":attr:`Cursor.is_readonly <apsw.Cursor.is_readonly>`"
        has_vdbe: bool
        ":attr:`Cursor.has_vdbe <apsw.Cursor.has_vdbe>`"
        bindings_count: int
        "How many :attr:`bindings <apsw.Cursor.bindings_count>` are in the query"
        bindings_names: tuple[str | None]
        "The :attr:`names <apsw.Cursor.bindings_names>`.  The leading marker (``?:@$``) is omitted"
        description: tuple[tuple[str, str], ...]
        ":meth:`Cursor.get_description <apsw.Cursor.get_description>`"
        description_full: tuple[tuple[str, str, str, str, str], ...] | None
        ":attr:`Cursor.description_full <apsw.Cursor.description_full>`"
        expanded_sql: str | None
        ":attr:`Cursor.expanded_sql <apsw.Cursor.expanded_sql>`"
        actions: list[QueryAction] | None
        """A list of the actions taken by the query, as discovered via
        :attr:`Connection.authorizer <apsw.Connection.authorizer>`"""
        explain: list[VDBEInstruction] | None
        """A list of instructions of the `internal code <https://sqlite.org/opcode.html>`__
        used by SQLite to execute the query"""
        query_plan: QueryPlan | None
        """The steps taken against tables and indices `described here <https://sqlite.org/eqp.html>`__"""

    @dataclass
    class QueryAction:
        """A :mod:`dataclass <dataclasses>` that provides information about one action taken by a query

        Depending on the action, only a subset of the fields will have non-None values"""

        action: int
        """`Authorizer code <https://sqlite.org/c3ref/c_alter_table.html>`__ (also present
        in :attr:`apsw.mapping_authorizer_function`)"""
        action_name: str
        """The string corresponding to the action.  For example `action` could be `21` in which
        case `action_name` will be `SQLITE_SELECT`"""

        column_name: str | None = None
        database_name: str | None = None
        "`main`, `temp`, the name in `ATTACH <https://sqlite.org/lang_attach.html>`__"
        file_name: str | None = None
        function_name: str | None = None
        module_name: str | None = None
        operation: str | None = None
        pragma_name: str | None = None
        pragma_value: str | None = None
        table_name: str | None = None
        trigger_name: str | None = None
        trigger_or_view: str | None = None
        """This action is happening due to a trigger or view, and not
        directly expressed in the query itself"""
        view_name: str | None = None

    @dataclass
    class QueryPlan:
        "A :mod:`dataclass <dataclasses>` for one step of a query plan"

        detail: str
        "Description of this step"
        sub: list[QueryPlan] | None = None
        "Steps that run inside this one"

    @dataclass
    class VDBEInstruction:
        "A :mod:`dataclass <dataclasses>` representing one instruction and its parameters"

        addr: int
        "Address of this opcode.  It will be the target of goto, loops etc"
        opcode: str
        "The instruction"
        comment: str | None = None
        "Additional human readable information"
        p1: int | None = None
        "First opcode parameter"
        p2: int | None = None
        "Second opcode parameter"
        p3: int | None = None
        "Third opcode parameter"
        p4: int | None = None
        "Fourth opcode parameter"
        p5: int | None = None
        "Fifth opcode parameter"

    @dataclass
    class DatabaseFileInfo:
        """Information about the main database file returned by :meth:`dbinfo`

        See `file format description <https://www.sqlite.org/fileformat.html#the_database_header>`__"""

        filename: str
        "database filena name"
        header: bytes
        "Header string"
        page_size: int
        "The database page size in bytes"
        write_format: int
        "File format write version. 1 for legacy; 2 for WAL"
        read_format: int
        "File format read version. 1 for legacy; 2 for WAL."
        reserved_bytes: int
        'Bytes of unused "reserved" space at the end of each page. Usually 0'
        file_change_counter: int
        "File change counter"
        page_count: int
        "Size of the database file in pages"
        freelist_pages: int
        "Total number of freelist pages"
        schema_cookie: int
        "The schema cookie"
        schema_format: int
        "The schema format number. Supported schema formats are 1, 2, 3, and 4"
        default_cache_size: int
        "The schema format number. Supported schema formats are 1, 2, 3, and 4"
        autovacuum_top_root: int
        "The page number of the largest root b-tree page when in auto-vacuum or incremental-vacuum modes, or zero otherwise"
        text_encoding: str
        "The database text encoding"
        user_version: int
        'The "user version" as read and set by the user_version pragma.'
        incremental_vacuum: bool
        "True (non-zero) for incremental-vacuum mode. False (zero) otherwise."
        application_id: int
        'The "Application ID" set by PRAGMA application_id'
        version_valid_for: int
        "The version-valid-for number."
        sqlite_version: int
        "SQLite version that lost wrote"

    @dataclass
    class JournalFileInfo:
        """Information about the rollback journal returned by :meth:`dbinfo`

        See the `file format description <https://www.sqlite.org/fileformat2.html#the_rollback_journal>`__"""

        filename: str
        "journal file name"
        header: bytes
        "Header string"
        header_valid: bool
        "If the header is the expected bytes"
        page_count: int
        'The "Page Count" - The number of pages in the next segment of the journal, or -1 to mean all content to the end of the file'
        random_nonce: int
        "A random nonce for the checksum"
        initial_pages: int
        "Initial size of the database in pages"
        sector_size: int
        "Size of a disk sector assumed by the process that wrote this journal"
        page_size: int
        "Size of pages in this journal"

    @dataclass
    class WALFileInfo:
        """Information about the rollback journal returned by :meth:`dbinfo`

        See the `file format description <https://www.sqlite.org/fileformat2.html#wal_file_format>`__"""

        filename: str
        "WAL file name"
        magic_number: int
        "Magic number"
        format_version: int
        "File format version. Currently 3007000"
        page_size: int
        "Database page size"
        checkpoint_sequence_number: int
        "Checkpoint sequence number"
        salt_1: int
        "Salt-1: random integer incremented with each checkpoint"
        salt_2: int
        "Salt-2: a different random number for each checkpoint"
        checksum_1: int
        "Checksum-1: First part of a checksum on the first 24 bytes of header"
        checksum_2: int
        "Checksum-2: Second part of the checksum on the first 24 bytes of header"