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They were based on the maximum possible key tuple length, which can be much larger than the real data size. The return value is used by handler::keyread_time(), which is used to estimate the cost of range access. This could cause range access not to be picked, even if it uses the clustered PK and reads about 8% of the table. The fix is to add KEY::stat_storage_length (next to KEY::rec_per_key) and have the storage engine fill it in handler::info(HA_STATUS_CONST). Currently, only InnoDB fills this based on its internal statistics: index->stat_index_size and ib_table->stat_n_rows. Also changed: - In handler::calculate_costs(), use ha_keyread_clustered_time() when computing clustered PK read cost, not ha_keyread_time(). The fix is OFF by default and enabled by setting FIX_INDEX_LOOKUP_COST flag in @@new_mode. |
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| archive | ||
| blackhole | ||
| columnstore | ||
| connect | ||
| csv | ||
| example | ||
| federated | ||
| federatedx | ||
| heap | ||
| innobase | ||
| maria | ||
| mroonga | ||
| myisam | ||
| myisammrg | ||
| oqgraph | ||
| perfschema | ||
| rocksdb | ||
| sequence | ||
| sphinx | ||
| spider | ||
| test_sql_discovery | ||