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WL#3527: Extend IGNORE INDEX so places where index is ignored
can be specified Currently MySQL allows one to specify what indexes to ignore during join optimization. The scope of the current USE/FORCE/IGNORE INDEX statement is only the FROM clause, while all other clauses are not affected. However, in certain cases, the optimizer may incorrectly choose an index for sorting and/or grouping, and produce an inefficient query plan. This task provides the means to specify what indexes are ignored/used for what operation in a more fine-grained manner, thus making it possible to manually force a better plan. We do this by extending the current IGNORE/USE/FORCE INDEX syntax to: IGNORE/USE/FORCE INDEX [FOR {JOIN | ORDER | GROUP BY}] so that: - if no FOR is specified, the index hint will apply everywhere. - if MySQL is started with the compatibility option --old_mode then an index hint without a FOR clause works as in 5.0 (i.e, the index will only be ignored for JOINs, but can still be used to compute ORDER BY). See the WL#3527 for further details.
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@ -2109,9 +2109,9 @@ int SQL_SELECT::test_quick_select(THD *thd, key_map keys_to_use,
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param.key_parts_end=key_parts;
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/* Calculate cost of full index read for the shortest covering index */
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if (!head->used_keys.is_clear_all())
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if (!head->covering_keys.is_clear_all())
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{
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int key_for_use= find_shortest_key(head, &head->used_keys);
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int key_for_use= find_shortest_key(head, &head->covering_keys);
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double key_read_time= (get_index_only_read_time(¶m, records,
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key_for_use) +
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(double) records / TIME_FOR_COMPARE);
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@ -4646,7 +4646,7 @@ static TRP_RANGE *get_key_scans_params(PARAM *param, SEL_TREE *tree,
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param->needed_reg->set_bit(keynr);
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bool read_index_only= index_read_must_be_used ? TRUE :
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(bool) param->table->used_keys.is_set(keynr);
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(bool) param->table->covering_keys.is_set(keynr);
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found_records= check_quick_select(param, idx, *key, update_tbl_stats);
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if (param->is_ror_scan)
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@ -8988,7 +8988,7 @@ get_best_group_min_max(PARAM *param, SEL_TREE *tree)
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cur_index_info++, cur_index++)
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{
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/* Check (B1) - if current index is covering. */
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if (!table->used_keys.is_set(cur_index))
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if (!table->covering_keys.is_set(cur_index))
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goto next_index;
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/*
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