diff options
Diffstat (limited to 'sql/sql_select.cc')
| -rw-r--r-- | sql/sql_select.cc | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 39eebd25814..b3e4bf39a8f 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -9094,11 +9094,6 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields, keyinfo->key_length+= key_part_info->length; } } - else - { - set_if_smaller(table->s->max_rows, rows_limit); - param->end_write_records= rows_limit; - } if (distinct && field_count != param->hidden_field_count) { @@ -9113,8 +9108,6 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields, null_pack_length-=hidden_null_pack_length; keyinfo->key_parts= ((field_count-param->hidden_field_count)+ test(null_pack_length)); - set_if_smaller(share->max_rows, rows_limit); - param->end_write_records= rows_limit; table->distinct= 1; share->keys= 1; if (blob_count) @@ -9169,6 +9162,20 @@ create_tmp_table(THD *thd,TMP_TABLE_PARAM *param,List<Item> &fields, 0 : FIELDFLAG_BINARY; } } + + /* + Push the LIMIT clause to the temporary table creation, so that we + materialize only up to 'rows_limit' records instead of all result records. + This optimization is not applicable when there is GROUP BY or there is + no GROUP BY, but there are aggregate functions, because both must be + computed for all result rows. + */ + if (!group && !thd->lex->current_select->with_sum_func) + { + set_if_smaller(table->s->max_rows, rows_limit); + param->end_write_records= rows_limit; + } + if (thd->is_fatal_error) // If end of memory goto err; /* purecov: inspected */ share->db_record_offset= 1; |