Sergei Petrunia 8db9aa496c MDEV-28268: Server crashes in Expression_cache_tracker::fetch_current_stats ...

(cherry-pick into preview-10.9-MDEV-27021-explain tree)

Expression_cache_tmptable object uses an Expression_cache_tracker object
to report the statistics.

In the common scenario, Expression_cache_tmptable destructor sets
tracker->cache=NULL. The tracker object survives after the expression
cache is deleted and one may call cache_tracker->fetch_current_stats()
for it with no harm.

However a degenerate cache with no parameters does not set
tracker->cache=NULL in Expression_cache_tmptable destructor which
results in an attempt to use freed data in the
cache_tracker->fetch_current_stats() call.

Fixed by setting tracker->cache to NULL and wrapping the assignment into
a function.

2022-04-29 11:00:37 +03:00

9.4 KiB

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