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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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| .. | ||
| audit_null | ||
| auth_dialog | ||
| auth_ed25519 | ||
| auth_examples | ||
| auth_gssapi | ||
| auth_pam | ||
| auth_pipe | ||
| auth_socket | ||
| aws_key_management | ||
| cracklib_password_check | ||
| daemon_example | ||
| debug_key_management | ||
| disks | ||
| example_key_management | ||
| feedback | ||
| file_key_management | ||
| fulltext | ||
| func_test | ||
| handler_socket | ||
| hashicorp_key_management | ||
| locale_info | ||
| metadata_lock_info | ||
| password_reuse_check | ||
| provider_bzip2 | ||
| provider_lz4 | ||
| provider_lzma | ||
| provider_lzo | ||
| provider_snappy | ||
| qc_info | ||
| query_response_time | ||
| server_audit | ||
| simple_password_check | ||
| sql_errlog | ||
| test_sql_service | ||
| type_geom | ||
| type_inet | ||
| type_mysql_json | ||
| type_test | ||
| type_uuid | ||
| user_variables | ||
| userstat | ||
| versioning | ||
| win_auth_client | ||
| wsrep_info | ||