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SELECT-initiated transactions can cause "database is locked" in sqlite #70812

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rhunter mannequin opened this issue Mar 23, 2016 · 2 comments
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SELECT-initiated transactions can cause "database is locked" in sqlite #70812

rhunter mannequin opened this issue Mar 23, 2016 · 2 comments
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stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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@rhunter
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rhunter mannequin commented Mar 23, 2016

BPO 26625
Superseder
  • bpo-9924: sqlite3 SELECT does not BEGIN a transaction, but should according to spec
    		•
    Files
  • unintuitive_sqlite_behavior.py
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = None
closed_at = <Date 2016-03-23.16:31:37.202>
created_at = <Date 2016-03-23.16:28:34.008>
labels = ['type-bug', 'library']
title = 'SELECT-initiated transactions can cause "database is locked" in sqlite'
updated_at = <Date 2016-03-23.17:29:08.114>
user = 'https://bugs.python.org/rhunter'

    bugs.python.org fields:

    activity = <Date 2016-03-23.17:29:08.114>
actor = 'berker.peksag'
assignee = 'none'
closed = True
closed_date = <Date 2016-03-23.16:31:37.202>
closer = 'rhunter'
components = ['Library (Lib)']
creation = <Date 2016-03-23.16:28:34.008>
creator = 'rhunter'
dependencies = []
files = ['42259']
hgrepos = []
issue_num = 26625
keywords = []
message_count = 2.0
messages = ['262282', '262283']
nosy_count = 1.0
nosy_names = ['rhunter']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '9924'
type = 'behavior'
url = 'https://bugs.python.org/issue26625'
versions = ['Python 2.7', 'Python 3.2', 'Python 3.3', 'Python 3.4', 'Python 3.5', 'Python 3.6']
    @rhunter
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    rhunter mannequin commented Mar 23, 2016

    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.

    @rhunter rhunter mannequin added stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error labels Mar 23, 2016
    @rhunter
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    rhunter mannequin commented Mar 23, 2016

    duplicate of bpo-9924

    @rhunter rhunter mannequin closed this as completed Mar 23, 2016
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
    @vient vient mentioned this issue Oct 19, 2023
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