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bug#13949735: crash regression from bug#13694811.

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There can be cases when the optimizer calls ha_partition::records_in_range
when there are no matching partitions. So the DBUG_ASSERT of
!tot_used_partitions does assert.

Fixed by returning 0 instead when no matching partitions are found.

This will avoid the crash. records_in_range will then try to find the
biggest used partition, which will not find any partition and
records_in_range will then return 0, meaning non rows can be found.

Patch contributed by Davi Arnaut at twitter.
This commit is contained in:
Mattias Jonsson 2012-05-15 12:45:52 +02:00
parent 18fec1e9c1
commit bed97f20ae
1 changed files with 11 additions and 1 deletions
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12
sql/ha_partition.cc
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@ -6322,7 +6322,17 @@ ha_rows ha_partition::min_rows_for_estimate()
DBUG_ENTER("ha_partition::min_rows_for_estimate"); DBUG_ENTER("ha_partition::min_rows_for_estimate");
tot_used_partitions= bitmap_bits_set(&m_part_info->used_partitions); tot_used_partitions= bitmap_bits_set(&m_part_info->used_partitions);
DBUG_ASSERT(tot_used_partitions);
/*
All partitions might have been left as unused during partition pruning
due to, for example, an impossible WHERE condition. Nonetheless, the
optimizer might still attempt to perform (e.g. range) analysis where an
estimate of the the number of rows is calculated using records_in_range.
Hence, to handle this and other possible cases, use zero as the minimum
number of rows to base the estimate on if no partition is being used.
*/
if (!tot_used_partitions)
DBUG_RETURN(0);
/* /*
Allow O(log2(tot_partitions)) increase in number of used partitions. Allow O(log2(tot_partitions)) increase in number of used partitions.