MDEV-32290: Server crashes in sub_select_cache#4972
Open
DaveGosselin-MariaDB wants to merge 1 commit into10.11from
Open
MDEV-32290: Server crashes in sub_select_cache#4972DaveGosselin-MariaDB wants to merge 1 commit into10.11from
DaveGosselin-MariaDB wants to merge 1 commit into10.11from
Conversation
DaveGosselin-MariaDB
force-pushed
the
10.11-mdev-32290-sub_select_cache-crash
branch
from
4602e4d to
98a7c7d
Compare
A query inside a UNION marked as uncacheable could crash during a subsequent execution on an assertion in sub_select_cache (like when a derived table is materialized again inside a recursive CTE) or in join_read_first because the cleanup at the end of one execution freed state that the next execution relies on. The cleanup decision in JOIN::join_free looked only at an individual SELECT_LEX's uncacheable flag. That flag does not propagate down from the enclosing unit to sibling branches, so a UNION "branch" would be cleaned up as if it were the only query even when the containing UNION is certain to run it again. Change the cleanup check to consider the unit's uncacheable flag (and not only the SELECT_LEX's) to keep state required on subsequent executions.
DaveGosselin-MariaDB
force-pushed
the
10.11-mdev-32290-sub_select_cache-crash
branch
from
98a7c7d to
ca74dee
Compare
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
A query inside a UNION marked as uncacheable could crash during a subsequent execution on an assertion in sub_select_cache (like when a derived table is materialized again inside a recursive CTE) or in join_read_first because the cleanup at the end of one execution freed state that the next execution relies on.
The cleanup decision in JOIN::join_free looked only at an individual SELECT_LEX's uncacheable flag. That flag does not propagate down from the enclosing unit to sibling branches, so a UNION "branch" would be cleaned up as if it were the only query even when the containing UNION is certain to run it again. Change the cleanup check to consider the unit's uncacheable flag (and not only the SELECT_LEX's) to keep state required on subsequent executions.