# Various interesting and useful bits of functionality

You need to import apsw.ext to use this module.

## Pretty printing

`format_query_table()` makes nicely formatted query output - see the the example.

## Logging and tracebacks

You can use `log_sqlite()` to forward SQLite log messages to the `logging` module.

`print_augmented_traceback()` prints an exception the usual way but also includes local variables, which APSW includes to make debugging quicker and easier.

## Virtual Tables

Use `index_info_to_dict()` to get `apsw.IndexInfo` in an easier to print and work with format.

Use `make_virtual_module()` to easily turn a Python function into a virtual table source.

`generate_series()` and `generate_series_sqlite()` provide generate_series.

## Query limiting, tracing and performance

Use `query_limit` with a block (example) to limit total number of rows processed or elapsed time.

Use `Trace` with a block (example) to see the SQL run and stats about each one such as timing, rows returned, changes made, memory used, and other SQLite counters.

Use `ShowResourceUsage` with a block (example) to get overall SQLite counters as well as operating system timing, cpu usage, memory, and I/O.

## Database storage usage

Use `analyze_pages()` to find out how much storage is in use, and how fragmented it is. See example output. It is also available graphically with `page_usage_to_svg()` - example output.

## Accessing result rows by column name

See the example.

Use `apsw.ext.DataClassRowFactory` as a `apsw.Connection.row_trace` for an entire connection, or `apsw.Cursor.row_trace` for a specific cursor.

## Converting types into and out of SQLite

SQLite only stores 5 types. (You can do any Python object as runtime only values.)

- None

- int

- float

- str

- bytes

Use `TypesConverterCursorFactory` as `apsw.Connection.cursor_factory` to adapt values going into SQLite, and convert them coming out. See the example.

To convert values going into SQLite, do either of:

- Inherit from `apsw.ext.SQLiteTypeAdapter` and define a to_sqlite_value method on the class

- Call `TypesConverterCursorFactory.register_adapter()` with the type and a adapter function

To adapt values coming out of SQLite:

- Call `TypesConverterCursorFactory.register_converter()` with the exact type string in the table and a converter function

## Detailed Query Information

SQLite can provide lots of information about queries. The `query_info()` function can gather them up for you. This includes:

- readonly if the query makes no direct changes

- first_query if multiple queries are provided

- actions which databases, tables, columns, functions, views etc are referenced - see actions

- query_plan which indices, tables scans etc are used to find the query results - see query plans

- explain for the low level steps taken inside SQLite - see SQLite bytecode

See the example.

## API Reference

apsw.ext.result_string(code: int) → str

  Turns a result or extended result code into a string. The appropriate mapping based on the value is used.

class apsw.ext.DataClassRowFactory(*, rename: bool = True, dataclass_kwargs: dict[str, Any] | None = None)

  Returns each row as a `dataclass`, accessible by column name.

  To use set an instance as `Connection.row_trace` to affect all `cursors`, 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 `connections` as you want.

  Parameters:

    - 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 `TypeError` raised by `dataclasses.make_dataclass()`

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

  get_dataclass(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 `description`

    This method caches its results.

  get_type(t: str | None) → Any

    Returns the `type hint` to use in the dataclass based on the type in the `description`

    SQLite’s affinity rules 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.

  __call__(cursor: Cursor, row: SQLiteValues) → Any

    What the row tracer calls

    This `looks up` the dataclass and column names, and then returns an instance of the dataclass.

class apsw.ext.SQLiteTypeAdapter

  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 `TypesConverterCursorFactory`

  abstractmethod to_sqlite_value() → SQLiteValue

    Return a SQLite compatible value for this object

class apsw.ext.TypesConverterCursorFactory(abstract_base_class: ABCMeta = SQLiteTypeAdapter)

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

  Parameters:

    abstract_base_class – Which metaclass to consider as conversion capable

  register_adapter(klass: type, callable: Callable[[Any], SQLiteValue]) → None

    Registers a callable that converts from klass to one of the supported SQLite types

  register_converter(name: str, callable: Callable[[SQLiteValue], Any]) → None

    Registers a callable that converts from a SQLite value

  __call__(connection: Connection) → TypeConverterCursor

    Returns a new convertor `cursor` for the connection

  adapt_value(value: Any) → SQLiteValue

    Returns SQLite representation of value

  convert_value(schematype: str, value: SQLiteValue) → Any

    Returns Python object from schema type and SQLite value

  wrap_bindings(bindings: Bindings | None) → Bindings | None

    Wraps bindings that are supplied to underlying execute

  wrap_sequence_bindings(sequenceofbindings: Iterable[Bindings]) → Generator[Bindings, None, None]

    Wraps a sequence of bindings that are supplied to the underlying executemany

  class DictAdapter(factory: TypesConverterCursorFactory, data: Mapping[str, SQLiteValue])

    Used to wrap dictionaries supplied as bindings

  class TypeConverterCursor(connection: Connection, factory: TypesConverterCursorFactory)

    Cursor used to do conversions

    execute(statements: str, bindings: Bindings | None = None, *, can_cache: bool = True, prepare_flags: int = 0, explain: int = -1) → Cursor

      Executes the statements doing conversions on supplied and returned values

      See `apsw.Cursor.execute()` for parameter details

    executemany(statements: str, sequenceofbindings: Iterable[Bindings], *, can_cache: bool = True, prepare_flags: int = 0, explain: int = -1) → Cursor

      Executes the statements against each item in sequenceofbindings, doing conversions on supplied and returned values

      See `apsw.Cursor.executemany()` for parameter details

apsw.ext.log_sqlite(*, level: int = logging.ERROR, logger: Logger | None = None) → None

  Send SQLite log messages to `logging`

  Parameters:

    - level – highest level to log at

    - logger – Use the specific logger

apsw.ext.print_augmented_traceback(exc_type: type[BaseException], exc_value: BaseException, exc_traceback: TracebackType, *, file: TextIO | None = None) → None

  Prints a standard exception, but also includes the value of variables in each stack frame which APSW adds to help diagnostics and debugging.

  Parameters:

    - exc_type – The exception type

    - exc_value – The exception value

    - exc_traceback – Traceback for the exception

    - file – (default `sys.stderr`) Where the print goes

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

apsw.ext.index_info_to_dict(o: IndexInfo, *, column_names: list[str] | None = None, rowid_name: str = '__ROWID__') → dict[str, Any]

  Returns a `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}

apsw.ext.dbinfo(db: 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. The headers are read using `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.

apsw.ext.find_columns(table_name: str, column_count: int, pk_columns: set[int], *, connection: Connection, schema: str | None = None) → tuple[str, ...]

  Finds a matching table and returns column names for `changeset_to_sql()`.

  Changesets only include column numbers, not column names so this method is used to find those names. Use it like this:

      changeset_to_sql(changeset, get_columns=functools.partial(apsw.ext.find_columns, connection=db))

  The table name has to match (following SQLite’s case insensitivity rules), have the correct number of columns, and corresponding primary key columns.

  Parameters:

    - table_name – Name of the expected table

    - column_count – How many columns there are

    - pk_columns – Which columns make up the primary key

    - connection – The connection to examine

    - schema – If `None` (default) then the `main` and all attached databases are searched, else only the named one.

  Raises:

    ValueError – If no corresponding table with matching column count and primary key columns can be found.

apsw.ext.changeset_to_sql(changeset: ChangesetInput, get_columns: Callable[[str, int, set[int]], tuple[str, ...]]) → Iterator[str]

  Produces SQL equivalent to the contents of a changeset (or patchset)

  Parameters:

    - changeset – The changeset either as bytes, or a streaming callable. It is passed to `apsw.Changeset.iter()`.

    - get_columns – Because changesets only have column numbers, this is called with a table name, column count, and primary keys, and should return the corresponding column names to use in the SQL. See `find_columns()`.

  SQL statements are provided one at a time, and will directly change one row. (More than one row can be affected due to foreign keys.) If a recorded row change was because of an indirect change then the SQL statement begins with the comment `/* indirect */`.

  See the example

class apsw.ext.Trace(file: TextIO | None, db: Connection, *, trigger: bool = False, vtable: bool = False, updates: bool = False, transaction: bool = False, truncate: int = 75, indent: str = '')

  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

  Parameters:

    - file – File to print to. If None then no information is gathered or printed

    - db – `Connection` to trace.

    - trigger – The names of triggers being executed is always shown. If this is True then each statement of an executing trigger is shown too.

    - vtable – If True then statements executed behind the scenes by virtual tables are shown.

    - updates – If True and the `preupdate_hook()` is available, then inserted, updated, and deleted rows are shown. This is very helpful when you use bindings.

    - transaction – If True then transaction start and commit/rollback will be shown, using commit/rollback hooks.

    - truncate – Truncates SQL text to this many characters

    - 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. If `updates` is on, then `INS`. `DEL`, and `UPD` are shown followed by the rowid, and then the columns. For updates, unchanged columns are shown as `...``. Transaction control is shown with a `!` prefix.

  As each statement ends you are shown summary information.

  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 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. This indicates an opportunity for an index.
  VmStep: 55,102 | How many internal steps were needed.
  Mem: 84.3KB | How much memory was used to hold the statement and working data.

  Tracing is done with `trace_v2()`.

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

  See the example.

class apsw.ext.ShowResourceUsage(file: TextIO | None, *, db: Connection | None = None, scope: 'thread' | 'process' | None = None, indent: str = '')

  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 example.

  Parameters:

    - file – File to print to. If None then no information is gathered or printed

    - db – `Connection` to gather SQLite stats from if not None. Statistics from each SQL statement executed are added together.

    - scope – Get `thread` or `process` stats, or None. Note that MacOS only supports process, and Windows doesn’t support either.

    - indent – Printed before each line of output

  Timing information comes from `time.monotonic()` and `time.process_time()`, resource usage from `resource.getrusage()` (empty for Windows), and SQLite from `trace_v2()`.

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

  See the example.

class apsw.ext.PageUsage(page_size: int, pages_used: int, sequential_pages: int, data_stored: int, cells: int, max_payload: int, tables: list[str], indices: list[str])

  Returned by `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 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

class apsw.ext.DatabasePageUsage(page_size: int, pages_used: int, sequential_pages: int, data_stored: int, cells: int, max_payload: int, tables: list[str], indices: list[str], pages_total: int, pages_freelist: int, max_page_count: int)

  Returned by `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

apsw.ext.analyze_pages(con: Connection, scope: int, schema: str = 'main') → DatabasePageUsage | dict[str, PageUsage]

  Summarizes page usage for the database

  The dbstat virtual table is used to gather statistics.

  See example output.

  Parameters:

    - con – Connection to use

    - scope –

      Value | Scope | Returns
      --- | --- | ---
      `0` | The database as a whole | `DatabasePageUsage`
      `1` | Tables and their indices are grouped together. Virtual tables like FTS5 have multiple backing tables which are grouped. | A `dict` where the key is the name of the table, and a corresponding `PageUsage` as the value. The `PageUsage.tables` and `PageUsage.indices` fields tell you which ones were included.
      `2` | Each table and index separately. | `dict` of each name and a corresponding `PageUsage` where one of the `PageUsage.tables` and `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 to check. If the table is not present then calling this function will give `apsw.SQLError` with message `no such table: dbstat`.

apsw.ext.page_usage_to_svg(con: Connection, out: TextIO, schema: str = 'main') → None

  Visualize database space usage as a 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 `analyze_pages()` to gather the information.

  Parameters:

    - con – Connection to query

    - out – Where the svg is written to. You can use `io.StringIO` if you want it as a string.

    - schema – Which attached database to query

  See example output.

exception apsw.ext.QueryLimitNoException

  Indicates that no exception will be raised when a `query_limit` is exceeded

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

  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.

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

  Parameters:

    - db – Connection to monitor

    - row_limit – Maximum number of rows to process, across all queries. `None` (default) means no limit

    - timeout – Maximum elapsed time in seconds. `None` (default) means no limit

    - row_exception – Class of exception to raise when row limit is hit

    - timeout_exception – Class of exception to raise when timeout is hit

    - timeout_steps – How often the elapsed time is checked in SQLite internal operations (see `set_progress_handler()`)

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

  Row limits are implemented by `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 `set_progress_handler()` to monitor the elapsed `time`. This means the elapsed time is only checked while running SQLite queries.

  `trace_v2()` and `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 example

apsw.ext.format_query_table(db: Connection, query: str, bindings: Bindings | None = None, *, colour: bool = False, quote: bool = False, string_sanitize: Callable[[str], str] | 0 | 1 | 2 = 0, binary: Callable[[bytes], str] = lambda x: ..., null: str = '(null)', truncate: int = 4096, truncate_val: str = ' ...', text_width: int = 80, use_unicode: bool = True) → str

  Produces query output in an attractive text table

  See the example.

  Parameters:

    - db – Connection to run the query on

    - query – Query to run

    - bindings – Bindings for query (if needed)

    - colour – If True then ANSI colours are used to outline the header, and show the type of each value.

    - quote – If True then `apsw.format_sql_value()` is used to get a textual representation of a value

    - 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'''

      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 `apsw.unicode.codepoint_name()`
      2 | hello.\……..world | All non-ascii characters and whitespace are replaced by a dot

    - binary – Called to convert bytes to string

    - null – How to represent the null value

    - truncate – How many characters to truncate long strings at (after sanitization)

    - truncate_val – Appended to truncated strings to show it was truncated

    - text_width – Maximum output width to generate

    - use_unicode – If True then unicode line drawing characters are used. If False then +—+ and | are used.

class apsw.ext.VTColumnAccess(*values)

  How the column value is accessed from a row, for `make_virtual_module()`

  By_Index = 1

    By number like with tuples and lists - eg `row[3]`

  By_Name = 2

    By name like with dicts - eg `row['quantity']`

  By_Attr = 3

    By attribute like with `dataclasses` - eg `row.quantity`

apsw.ext.get_column_names(row: Any) → tuple[Sequence[str], VTColumnAccess]

  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 `dataclass`)

  Type | Access | Column names From
  --- | --- | ---
  `dataclasses.is_dataclass()` | `VTColumnAccess.By_Attr` | `dataclasses.fields()`
  `isinstance`(`tuple`) and `hasattr`(`"_fields"`) - eg `namedtuple()` | `VTColumnAccess.By_Index` | `row._fields`
  `hasattr`(`"__match_args__"`) | `VTColumnAccess.By_Attr` | `row.__match_args__` (if not empty)
  `isinstance`(`dict`) | `VTColumnAccess.By_Name` | `dict.keys()`
  `isinstance`(`tuple`) | `VTColumnAccess.By_Index` | `columnX` where X is zero up to `len`(`row`)

  Example usage:

      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)

apsw.ext.make_virtual_module(db: 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 `VTColumnAccess` saying how to access columns from a row. See `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 for parameters:

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

  `inspect.signature()` is used to discover parameter names.

  Positional parameters to callable come from the table definition.

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

  Keyword arguments come from WHERE clauses.

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

  `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.

  Parameters:

    - eponymous – Lets you use the name as a table name without having to create a virtual table

    - eponymous_only – Can only reference as a table name

    - repr_invalid – If True then values that are not valid `apsw.SQLiteValue` will be converted to a string using `repr()`

  See the example

  ### Advanced

  The callable may also have an attribute named primary_key. By default the `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 `apsw.SQLError` and a message from SQLite of “no query solution”

apsw.ext.generate_series_sqlite(start=None, stop=0xFFFFFFFF, step=1)

  Behaves like SQLite’s generate_series

  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))

  See also

  `generate_series()`

apsw.ext.generate_series(start, stop, step=None)

  Behaves like Postgres and SQL Server

  Postgres doc SQL server doc

  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))

  See also

  `generate_series_sqlite()`

apsw.ext.query_info(db: Connection, query: str, bindings: 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.

  See the example.

class apsw.ext.QueryDetails(query: str, bindings: Bindings | None, first_query: str, query_remaining: str | None, is_explain: int, is_readonly: bool, has_vdbe: bool, bindings_count: int, bindings_names: tuple[str | None], description: tuple[tuple[str, str], ...], description_full: tuple[tuple[str, str, str, str, str], ...] | None, expanded_sql: str | None, actions: list[QueryAction] | None, explain: list[VDBEInstruction] | None, query_plan: QueryPlan | None)

  A `dataclass` that provides detailed information about a query, returned by `query_info()`

  query: str

    Original query provided

  bindings: 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

    `Cursor.is_explain`

  is_readonly: bool

    `Cursor.is_readonly`

  has_vdbe: bool

    `Cursor.has_vdbe`

  bindings_count: int

    How many `bindings` are in the query

  bindings_names: tuple[str | None]

    The `names`. The leading marker (`?:@$`) is omitted

  description: tuple[tuple[str, str], ...]

    `Cursor.get_description`

  description_full: tuple[tuple[str, str, str, str, str], ...] | None

    `Cursor.description_full`

  expanded_sql: str | None

    `Cursor.expanded_sql`

  actions: list[QueryAction] | None

    A list of the actions taken by the query, as discovered via `Connection.authorizer`

  explain: list[VDBEInstruction] | None

    A list of instructions of the internal code used by SQLite to execute the query

  query_plan: QueryPlan | None

    The steps taken against tables and indices described here

class apsw.ext.QueryAction(action: int, action_name: str, column_name: str | None = None, database_name: str | None = None, 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, view_name: str | None = None)

  A `dataclass` 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 (also present in `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

  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

class apsw.ext.QueryPlan(detail: str, sub: list[QueryPlan] | None = None)

  A `dataclass` for one step of a query plan

  detail: str

    Description of this step

  sub: list[QueryPlan] | None = None

    Steps that run inside this one

class apsw.ext.VDBEInstruction(addr: int, opcode: str, comment: str | None = None, p1: int | None = None, p2: int | None = None, p3: int | None = None, p4: int | None = None, p5: int | None = None)

  A `dataclass` 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

class apsw.ext.DatabaseFileInfo(filename: str, header: bytes, page_size: int, write_format: int, read_format: int, reserved_bytes: int, file_change_counter: int, page_count: int, freelist_pages: int, schema_cookie: int, schema_format: int, default_cache_size: int, autovacuum_top_root: int, text_encoding: str, user_version: int, incremental_vacuum: bool, application_id: int, version_valid_for: int, sqlite_version: int)

  Information about the main database file returned by `dbinfo()`

  See file format description

  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

class apsw.ext.JournalFileInfo(filename: str, header: bytes, header_valid: bool, page_count: int, random_nonce: int, initial_pages: int, sector_size: int, page_size: int)

  Information about the rollback journal returned by `dbinfo()`

  See the file format description

  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

class apsw.ext.WALFileInfo(filename: str, magic_number: int, format_version: int, page_size: int, checkpoint_sequence_number: int, salt_1: int, salt_2: int, checksum_1: int, checksum_2: int)

  Information about the rollback journal returned by `dbinfo()`

  See the file format description

  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