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MDEV-12136 SELECT COUNT(DISTINCT) returns the wrong value when tmp_table_size is limited

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Same MDEV, second bug.
Merge buffer must fit at least MERGEBUFF2 (that is, 15) key values.
Because merge_index() can merge that many buffers, and
merge_many_buff() leaves that many buffers unmerged.
This commit is contained in:
Sergei Golubchik 2017-07-12 19:31:01 +02:00
commit 27bc13b7a2
3 changed files with 12 additions and 2 deletions
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8
sql/uniques.cc
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@ -607,11 +607,15 @@ bool Unique::walk(TABLE *table, tree_walk_action action, void *walk_action_arg)
return 1;
if (flush_io_cache(&file) || reinit_io_cache(&file, READ_CACHE, 0L, 0, 0))
return 1;
size_t buff_sz= (max_in_memory_size / full_size + 1) * full_size;
/*
merge_buffer must fit at least MERGEBUFF2 keys, because
merge_index() can merge that many BUFFPEKs at once.
*/
size_t buff_sz= max(MERGEBUFF2, max_in_memory_size/full_size+1) * full_size;
if (!(merge_buffer = (uchar *)my_malloc(buff_sz, MYF(MY_WME))))
return 1;
if (buff_sz < (ulong) (full_size * (file_ptrs.elements + 1)))
res= merge(table, merge_buffer, buff_sz >= full_size * MERGEBUFF2) ;
res= merge(table, merge_buffer, true) ;
if (!res)
{