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MDEV-19834 Selectivity of an equality condition discounted twice

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When discounting selectivity of ref access, don't discount the
selectivity we've already discounted for range access.

The 10.1 version of the fix. Will need to adjust condition filtering
test results in 10.4
This commit is contained in:
Sergei Petrunia
2019-08-15 12:57:21 +03:00
parent 588e67956a
commit 1c75ad6eed
3 changed files with 67 additions and 6 deletions
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15
sql/sql_select.cc
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@ -7618,6 +7618,7 @@ double table_cond_selectivity(JOIN *join, uint idx, JOIN_TAB *s,
KEYUSE *keyuse= pos->key;
KEYUSE *prev_ref_keyuse= keyuse;
uint key= keyuse->key;
bool used_range_selectivity= false;
/*
Check if we have a prefix of key=const that matches a quick select.
@ -7643,6 +7644,7 @@ double table_cond_selectivity(JOIN *join, uint idx, JOIN_TAB *s,
keyparts++;
}
sel /= (double)table->quick_rows[key] / (double) table->stat_records();
used_range_selectivity= true;
}
}
@ -7678,13 +7680,14 @@ double table_cond_selectivity(JOIN *join, uint idx, JOIN_TAB *s,
if (keyparts > keyuse->keypart)
{
/* Ok this is the keyuse that will be used for ref access */
uint fldno;
if (is_hash_join_key_no(key))
fldno= keyuse->keypart;
else
fldno= table->key_info[key].key_part[keyparts-1].fieldnr - 1;
if (keyuse->val->const_item())
if (!used_range_selectivity && keyuse->val->const_item())
{
uint fldno;
if (is_hash_join_key_no(key))
fldno= keyuse->keypart;
else
fldno= table->key_info[key].key_part[keyparts-1].fieldnr - 1;
if (table->field[fldno]->cond_selectivity > 0)
{
sel /= table->field[fldno]->cond_selectivity;