Description

erlend-aasland

opened on Aug 22, 2021

Issue body actions

BPO	44976
Nosy	@berkerpeksag, @serhiy-storchaka, @pablogsal, @erlend-aasland
PRs	bpo-44976: Lazy creation of sqlite3 result rows #27884

^{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 2021-08-25.10:29:18.621>
created_at = <Date 2021-08-22.09:06:30.968>
labels = ['extension-modules', 'type-feature']
title = '[sqlite3] lazy creation of result rows'
updated_at = <Date 2021-08-25.10:29:18.620>
user = 'https://github.com/erlend-aasland'

bugs.python.org fields:

activity = <Date 2021-08-25.10:29:18.620>
actor = 'pablogsal'
assignee = 'none'
closed = True
closed_date = <Date 2021-08-25.10:29:18.621>
closer = 'pablogsal'
components = ['Extension Modules']
creation = <Date 2021-08-22.09:06:30.968>
creator = 'erlendaasland'
dependencies = []
files = []
hgrepos = []
issue_num = 44976
keywords = ['patch']
message_count = 3.0
messages = ['400062', '400065', '400252']
nosy_count = 4.0
nosy_names = ['berker.peksag', 'serhiy.storchaka', 'pablogsal', 'erlendaasland']
pr_nums = ['27884']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue44976'
versions = []

Activity

1. erlend-aasland commented on Aug 22, 2021

   

   erlend-aasland

   on Aug 22, 2021

   ContributorAuthor

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   Currently, we build the first result row in the _pysqlite_query_execute() loop if sqlite3_step() returned SQLITE_ROW. When the user asks for a row (for example, using sqlite3.Cursor.fetchone()), this pre-built row is returned, and the next row is prepared.

   Suggesting to lazily build result rows instead.

   Cons:

   • no result tuples are built unless sqlite3.Cursor.fetch*() is called
   • no need to keep the next result row (tuple) in pysqlite_Cursor; rows are built on demand
   • pysqlite_cursor_iternext() is vastly simplified (50% less lines of code)
   • the main loop in _pysqlite_query_execute() is further simplified

   Cons:

   • code churn

   git diff main --shortstat: 2 files changed, 29 insertions(+), 58 deletions(-)
2. erlend-aasland

   added

   extension-modulesC modules in the Modules dirC modules in the Modules dir

   type-featureA feature request or enhancementA feature request or enhancement

   on Aug 22, 2021
3. erlend-aasland commented on Aug 22, 2021

   

   erlend-aasland

   on Aug 22, 2021

   ContributorAuthor

   More actions

   Historical note:
   The current behaviour was introduced in pysqlite v2.0.2 (May 21 2005), in order to be able to finalise statements and thus close cursors as soon as possible. However, that effect was cancelled just after a couple of months, by the addition of the LRU cache and the ability to reuse prepared statements.
4. pablogsal commented on Aug 25, 2021

   

   pablogsal

   on Aug 25, 2021

   Member

   More actions

   New changeset 3df0fc8 by Erlend Egeberg Aasland in branch 'main':
   bpo-44976: Lazy creation of sqlite3 result rows (GH-27884)
   3df0fc8
5. pablogsal

   closed this as completedon Aug 25, 2021
6. pablogsal

   closed this as completedon Aug 25, 2021
7. ezio-melotti

   transferred this issue fromon Apr 10, 2022
8. erlend-aasland

   added

   topic-sqlite3

   on May 16, 2022

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