Igor Babaev b34bb81eaf MDEV-25112 MIN/MAX aggregation over an indexed column may return wrong result ...

If a query with implicit grouping contains in MIN/MAX set function in the
select list over a column that is a part of an index then the query
might be subject to MIN/MAX optimization. With this optimization the
server performs a look-up into an index, fetches a value of the column C
used in the MIN/MAX function and substitute the MIN/MAX expression for this
value. This allows to eliminate the table containing C from further join
processing. In order the optimization to be applied the WHERE condition
must be a conjunction of simple equality/inequality predicates or/and
BETWEEN predicates.
The bug fixed in the patch resulted in fetching a wrong value from the
index used for MIN/MAX optimization. It may happened when a BETWEEN
predicate containing the MIN/MAX value followed a strict inequality.

Approved by dmitry.shulga@mariadb.com

2021-03-18 09:54:49 -07:00

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