From: Gord Thompson Date: Wed, 29 Jun 2022 13:38:38 +0000 (-0600) Subject: Document user-defined functions for sqlite X-Git-Tag: rel_2_0_0b1~34^2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=48a0df55c1cfb8746eec8073c0feb05be1652665;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git Document user-defined functions for sqlite Change-Id: I64e4d4dce8c5f5aced3190f9e3682c630462a61e --- diff --git a/lib/sqlalchemy/dialects/sqlite/aiosqlite.py b/lib/sqlalchemy/dialects/sqlite/aiosqlite.py index 93c1a499d5..97ea1b2b36 100644 --- a/lib/sqlalchemy/dialects/sqlite/aiosqlite.py +++ b/lib/sqlalchemy/dialects/sqlite/aiosqlite.py @@ -36,6 +36,14 @@ This dialect should normally be used only with the The URL passes through all arguments to the ``pysqlite`` driver, so all connection arguments are the same as they are for that of :ref:`pysqlite`. +.. _aiosqlite_udfs: + +User-Defined Functions +---------------------- + +aiosqlite extends pysqlite to support async, so we can create our own user-defined functions (UDFs) +in Python and use them directly in SQLite queries as described here: :ref:`pysqlite_udfs`. + """ # noqa diff --git a/lib/sqlalchemy/dialects/sqlite/pysqlite.py b/lib/sqlalchemy/dialects/sqlite/pysqlite.py index f155fed365..19949441fb 100644 --- a/lib/sqlalchemy/dialects/sqlite/pysqlite.py +++ b/lib/sqlalchemy/dialects/sqlite/pysqlite.py @@ -406,6 +406,39 @@ by adding the desired locking mode to our ``"BEGIN"``:: `sqlite3 module breaks transactions and potentially corrupts data `_ - on the Python bug tracker +.. _pysqlite_udfs: + +User-Defined Functions +---------------------- + +pysqlite supports a `create_function() `_ +method that allows us to create our own user-defined functions (UDFs) in Python and use them directly in SQLite queries. +These functions are registered with a specific DBAPI Connection. + +SQLAlchemy uses connection pooling with file-based SQLite databases, so we need to ensure that the UDF is attached to the +connection when it is created. That is accomplished with an event listener:: + + from sqlalchemy import create_engine + from sqlalchemy import event + from sqlalchemy import text + + + def udf(): + return "udf-ok" + + + engine = create_engine("sqlite:///./db_file") + + + @event.listens_for(engine, "connect") + def connect(conn, rec): + conn.create_function("udf", 0, udf) + + + for i in range(5): + with engine.connect() as conn: + print(conn.scalar(text("SELECT UDF()"))) + """ # noqa