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Thank you for your contribution! This is a preliminary review.
Very close, but I'd like to see a clearer test case before I approve it.
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HAVING can read stale aggregate and field values when grouped rows are copied into a second temporary table for DISTINCT. Rechecking the same condition during duplicate removal can then discard qualifying rows. Bind HAVING references to the stored values of the completed groups. Evaluate the condition while writing the DISTINCT table, and avoid attaching or evaluating it again against that table. Add one grouped query with two qualifying groups that produce the same output and one rejected group. Check that DISTINCT returns the single qualifying row. Use the default test environment without extra session settings, a separate database or equivalent query variants. Bug report: https://jira.mariadb.org/browse/MDEV-40779
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DISTINCT + char_length(SPACE(AVG(…))) + HAVING returns empty for one insertion order of the same rows
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LGTM. Thanks. Please stand by for the final review.
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HAVING can read stale aggregate and field values when grouped rows are
copied into a second temporary table for DISTINCT. Rechecking the condition
during duplicate removal can discard qualifying rows.
Bind HAVING to the stored values of the completed groups. Evaluate it while
writing the DISTINCT table, and avoid attaching or evaluating it again
against that table.
Bug report: https://jira.mariadb.org/browse/MDEV-40779
Regression coverage
Reduce the addition to
main.func_groupfrom 67 lines to five: an issueheader, table creation, three input rows, one query and cleanup. Two groups
satisfy HAVING and produce the same output; a third group fails HAVING. The
expected DISTINCT result is one row,
(2, 2).Remove the extra InnoDB include, session settings, separate database,
sorting directives, equivalent query variants and manual prepared statements.
The original source fix and existing test contents are preserved.
Validation
On current
11.4atf49e838d367f2154b3edb43effa99ff9eb0d8602:main.func_grouponly because thenew query returns no rows instead of
(2, 2).main.func_group,main.group_by,main.having,main.select,main.distinctandmain.view.main.func_grouppasses with the view protocol.with the prepared-statement protocol, including its automatic repeated
SELECT execution. The existing full
main.func_grouptest disables thatprotocol at its start.