planner: disable LOCK IN SHARE MODE by default (#19506)#21005
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ti-srebot merged 3 commits intopingcap:release-4.0from Nov 17, 2020
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planner: disable LOCK IN SHARE MODE by default (#19506)#21005ti-srebot merged 3 commits intopingcap:release-4.0from
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@nullnotnil please resolve the code conflict. |
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cherry-pick #19506 to release-4.0
What problem does this PR solve?
Issue Number: fixes #19383
Problem Summary:
SELECT LOCK IN SHARE MODEis described in the manual as a noop. But that's not obvious to new users.This protects against incorrect usage via the enable_noop_functions flag; meaning that applications that want to execute the query and receive broken results have a way out.
(In the fix in master, this also disabled
SQL_CALC_FOUND_ROWSby default. But in this cherry-pick I've removed that, as I think it will break a lot more applications than are expected between point releases.)What is changed and how it works?
What's Changed:
Queries using LOCK IN SHARE MODE now get an error by default.
Related changes
Docs PR pingcap/docs#3898
Check List
Tests
Side effects
Release note
LOCK IN SHARE MODE. This helps alert users that this feature is not implemented by TiDB, but a workaround to restore the previous behavior is available by settingtidb_enable_noop_functions=1.