[issue26625] SELECT-initiated transactions can cause "database is locked" in sqlite

[Berker Peksag]

Changes by Berker Peksag :


--
stage:  -> resolved
superseder:  -> sqlite3 SELECT does not BEGIN a transaction, but should 
according to spec

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[issue26625] SELECT-initiated transactions can cause "database is locked" in sqlite

[Rian Hunter]

Rian Hunter added the comment:

duplicate of #9924

--
resolution:  -> duplicate
status: open -> closed

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[issue26625] SELECT-initiated transactions can cause "database is locked" in sqlite

[Rian Hunter]

New submission from Rian Hunter:

When a transaction starts with a SELECT statement this can invoke a "database 
is locked" error if the SELECT statement is not exhausted or explicitly closed.

This can lead to subtle "database is locked" bugs, even when a large timeout is 
set on the connection. Many, many people are affected by this bug (search the 
web for "python sqlite database is locked").

The attached code demonstrates this bug and possible (unintuitive) fixes. The 
best workaround is to "explicitly" start a transaction in these cases by 
issuing a dummy DML statement. This seems very clumsy.

My proposed fix is to implicitly open a transaction before all non-DDL 
statements (including SELECT statements), not just DML statements.

If there won't be a fix soon, then at least the documentation should note this 
quirky behavior.

--
components: Library (Lib)
files: unintuitive_sqlite_behavior.py
messages: 262282
nosy: rhunter
priority: normal
severity: normal
status: open
title: SELECT-initiated transactions can cause "database is locked" in sqlite
type: behavior
versions: Python 2.7, Python 3.2, Python 3.3, Python 3.4, Python 3.5, Python 3.6
Added file: http://bugs.python.org/file42259/unintuitive_sqlite_behavior.py

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