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3fa99f0c0e
The main difference in code path between EQ_REF and REF is that for REF we have to do an extra read_next on the index to check that there is no more matching rows. Before this patch we added a preference of EQ_REF by ensuring that REF would always estimate to find at least 2 rows. This patch adds the cost of the extra key read_next to REF access and removes the code that limited REF to at least 2 rows. For some queries this can have a big effect as the total estimated rows will be halved for each REF table with 1 rows. multi_range cost calculations are also changed to take into account the difference between EQ_REF and REF. The effect of the patch to the test suite: - About 80 test case changed - Almost all changes where for EXPLAIN where estimated rows for REF where changed from 2 to 1. - A few test cases using explain extended had a change of 'filtered'. This is because of the estimated rows are now closer to the calculated selectivity. - A very few test had a change of table order. This is because the change of estimated rows from 2 to 1 or the small cost change for REF (main.subselect_sj_jcl6, main.group_by, main.dervied_cond_pushdown, main.distinct, main.join_nested, main.order_by, main.join_cache) - No key statistics and the estimated rows are now smaller which cased estimated filtering to be lower. (main.subselect_sj_mat) - The number of total rows are halved. (main.derived_cond_pushdown) - Plans with 1 row changed to use RANGE instead of REF. (main.group_min_max) - ALL changed to REF (main.key_diff) - Key changed from ref + index_only to PRIMARY key for InnoDB, as OPTIMIZER_ROW_LOOKUP_COST + OPTIMIZER_ROW_NEXT_FIND_COST is smaller than OPTIMIZER_KEY_LOOKUP_COST + OPTIMIZER_KEY_NEXT_FIND_COST. (main.join_outer_innodb) - Cost changes printouts (main.opt_trace*) - Result order change (innodb_gis.rtree) |
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| .. | ||
| alter.result | ||
| autoinc.result | ||
| binlog.result | ||
| commit_id.result | ||
| create.result | ||
| cte.result | ||
| data.result | ||
| debug.result | ||
| delete.result | ||
| delete_history.result | ||
| derived.result | ||
| foreign.result | ||
| insert.result | ||
| insert2.result | ||
| load_data.result | ||
| misc.result | ||
| not_embedded.result | ||
| online.result | ||
| optimized.result | ||
| partition,heap.rdiff | ||
| partition.result | ||
| replace.result | ||
| rpl.result | ||
| rpl_mix.result | ||
| rpl_row.result | ||
| rpl_stmt.result | ||
| select.result | ||
| select2,trx_id.rdiff | ||
| select2.result | ||
| simple.result | ||
| sysvars.result | ||
| trx_id.result | ||
| update,trx_id.rdiff | ||
| update-big.result | ||
| update.result | ||
| view.result | ||