database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2026-01-06 05:22:24 +03:00
Code Activity

Bug#53806: Wrong estimates for range query in partitioned MyISAM table

Browse Source 
Bug#46754: 'rows' field doesn't reflect partition pruning

The EXPLAIN's result in 'rows' field
was evaluated to number of rows when the table was opened
(not from the table cache) and only the partitions left
after pruning was updated with its correct number
of rows.

The evaluation of the 'rows' field was using handler::records()
which is a potentially expensive call, and ignores the partitioning
pruning.

The fix was to use the handlers stats.records after updating it
with ::info(HA_STATUS_VARIABLE) instead.
This commit is contained in:
Mattias Jonsson
2010-08-26 17:14:18 +02:00
parent 6973c354de
commit 50150fd66a
3 changed files with 299 additions and 243 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
sql/sql_select.cc
View File

@@ -16640,7 +16640,15 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
if (tab->select && tab->select->quick)
examined_rows= tab->select->quick->records;
else if (tab->type == JT_NEXT || tab->type == JT_ALL)
examined_rows= tab->limit ? tab->limit : tab->table->file->records();
{
if (tab->limit)
examined_rows= tab->limit;
else
{
tab->table->file->info(HA_STATUS_VARIABLE);
examined_rows= tab->table->file->stats.records;
}
}
else
examined_rows=(ha_rows)join->best_positions[i].records_read;