WIP MDEV-35168: Potential Bug in Database Handling of NULL Values in EXIS… #4327
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DaveGosselin-MariaDB
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…TS Clause
Queries of the form
SELECT ... FROM (SELECT constant AS alias_N FROM t0) dt ... WHERE EXISTS
(SELECT ... WHERE (dt.alias_N ...));
must force derived table dt to be materialized, or the WHERE EXISTS will
not filter rows correctly. If we allow derived table dt to be merged,
then references to dt.alias_N are replaced with their constant values
directly, so a WHERE EXISTS subquery will attempt to filter rows from the
outer query based on those constant values rather than the columns'
values computed during outer query evaluation.
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spetrunia
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Oct 14, 2025
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Please check out the comments at https://jira.mariadb.org/browse/MDEV-35168.
I've put them there because they are quite general and may be out of scope of this patch.
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…TS Clause
Queries of the form
must force derived table
dtto be materialized, or theWHERE EXISTSwill not filter rows correctly. If we allow derived tabledtto be merged, then references todt.alias_Nare replaced with their constant values directly, so aWHERE EXISTSsubquery will attempt to filter rows from the outer query based on those constant values rather than the columns' values computed during outer query evaluation.Note that this is a WIP