diff options
Diffstat (limited to 'sql/sql_select.cc')
| -rw-r--r-- | sql/sql_select.cc | 98 |
1 files changed, 75 insertions, 23 deletions
diff --git a/sql/sql_select.cc b/sql/sql_select.cc index d126d0e4ec6..10884a95b74 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -44,7 +44,7 @@ #include "sql_partition.h" // make_used_partitions_str #include "sql_acl.h" // *_ACL #include "sql_test.h" // print_where, print_keyuse_array, - // print_sjm, print_plan + // print_sjm, print_plan, TEST_join #include "records.h" // init_read_record, end_read_record #include "filesort.h" // filesort_free_buffers #include "sql_union.h" // mysql_union @@ -90,8 +90,10 @@ static bool best_extension_by_limited_search(JOIN *join, double read_time, uint depth, uint prune_level); static uint determine_search_depth(JOIN* join); +C_MODE_START static int join_tab_cmp(const void* ptr1, const void* ptr2); static int join_tab_cmp_straight(const void* ptr1, const void* ptr2); +C_MODE_END /* TODO: 'find_best' is here only temporarily until 'greedy_search' is tested and approved. @@ -1126,9 +1128,8 @@ JOIN::optimize() } } - if (conds &&!outer_join && const_table_map != found_const_table_map && - (select_options & SELECT_DESCRIBE) && - select_lex->master_unit() == &thd->lex->unit) // upper level SELECT + if (conds && const_table_map != found_const_table_map && + (select_options & SELECT_DESCRIBE)) { conds=new Item_int((longlong) 0,1); // Always false } @@ -1145,13 +1146,13 @@ JOIN::optimize() elements may be lost during further having condition transformation in JOIN::exec. */ - if (having && !having->with_sum_func) + if (having && const_table_map) { - COND *const_cond= make_cond_for_table(having, const_table_map, 0); - DBUG_EXECUTE("where", print_where(const_cond, "const_having_cond", - QT_ORDINARY);); - if (const_cond && !const_cond->val_int()) + having->update_used_tables(); + having= remove_eq_conds(thd, having, &having_value); + if (having_value == Item::COND_FALSE) { + having= new Item_int((longlong) 0,1); zero_result_cause= "Impossible HAVING noticed after reading const tables"; error= 0; DBUG_RETURN(0); @@ -3006,8 +3007,7 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables_arg, COND *conds, s->quick=select->quick; s->needed_reg=select->needed_reg; select->quick=0; - if (records == 0 && s->table->reginfo.impossible_range && - (s->table->file->ha_table_flags() & HA_STATS_RECORDS_IS_EXACT)) + if (records == 0 && s->table->reginfo.impossible_range) { /* Impossible WHERE or ON expression @@ -5162,6 +5162,11 @@ greedy_search(JOIN *join, if (best_extension_by_limited_search(join, remaining_tables, idx, record_count, read_time, search_depth, prune_level)) DBUG_RETURN(TRUE); + /* + 'best_read < DBL_MAX' means that optimizer managed to find + some plan and updated 'best_positions' array accordingly. + */ + DBUG_ASSERT(join->best_read < DBL_MAX); if (size_remain <= search_depth) { @@ -8942,8 +8947,14 @@ simplify_joins(JOIN *join, List<TABLE_LIST> *join_list, COND *conds, bool top) we still make the inner tables dependent on the outer tables. It would be enough to set dependency only on one outer table for them. Yet this is really a rare case. + Note: + RAND_TABLE_BIT mask should not be counted as it + prevents update of inner table dependences. + For example it might happen if RAND() function + is used in JOIN ON clause. */ - if (!(prev_table->on_expr->used_tables() & ~prev_used_tables)) + if (!((prev_table->on_expr->used_tables() & ~RAND_TABLE_BIT) & + ~prev_used_tables)) prev_table->dep_tables|= used_tables; } } @@ -9199,6 +9210,46 @@ static bool check_interleaving_with_nj(JOIN_TAB *next_tab) /** Nested joins perspective: Remove the last table from the join order. + The algorithm is the reciprocal of check_interleaving_with_nj(), hence + parent join nest nodes are updated only when the last table in its child + node is removed. The ASCII graphic below will clarify. + + %A table nesting such as <tt> t1 x [ ( t2 x t3 ) x ( t4 x t5 ) ] </tt>is + represented by the below join nest tree. + + @verbatim + NJ1 + _/ / \ + _/ / NJ2 + _/ / / \ + / / / \ + t1 x [ (t2 x t3) x (t4 x t5) ] + @endverbatim + + At the point in time when check_interleaving_with_nj() adds the table t5 to + the query execution plan, QEP, it also directs the node named NJ2 to mark + the table as covered. NJ2 does so by incrementing its @c counter + member. Since all of NJ2's tables are now covered by the QEP, the algorithm + proceeds up the tree to NJ1, incrementing its counter as well. All join + nests are now completely covered by the QEP. + + restore_prev_nj_state() does the above in reverse. As seen above, the node + NJ1 contains the nodes t2, t3, and NJ2. Its counter being equal to 3 means + that the plan covers t2, t3, and NJ2, @e and that the sub-plan (t4 x t5) + completely covers NJ2. The removal of t5 from the partial plan will first + decrement NJ2's counter to 1. It will then detect that NJ2 went from being + completely to partially covered, and hence the algorithm must continue + upwards to NJ1 and decrement its counter to 2. %A subsequent removal of t4 + will however not influence NJ1 since it did not un-cover the last table in + NJ2. + + SYNOPSIS + restore_prev_nj_state() + last join table to remove, it is assumed to be the last in current + partial join order. + + DESCRIPTION + Remove the last table from the partial join order and update the nested joins counters and join->cur_embedding_map. It is ok to call this function for the first table in join order (for which @@ -9212,19 +9263,20 @@ static void restore_prev_nj_state(JOIN_TAB *last) { TABLE_LIST *last_emb= last->table->pos_in_table_list->embedding; JOIN *join= last->join; - while (last_emb) + for (;last_emb != NULL; last_emb= last_emb->embedding) { - if (!(--last_emb->nested_join->counter)) - join->cur_embedding_map&= ~last_emb->nested_join->nj_map; - else if (last_emb->nested_join->join_list.elements-1 == - last_emb->nested_join->counter) - { - join->cur_embedding_map|= last_emb->nested_join->nj_map; - break; - } - else + NESTED_JOIN *nest= last_emb->nested_join; + DBUG_ASSERT(nest->counter > 0); + + bool was_fully_covered= nest->is_fully_covered(); + + if (--nest->counter == 0) + join->cur_embedding_map&= ~nest->nj_map; + + if (!was_fully_covered) break; - last_emb= last_emb->embedding; + + join->cur_embedding_map|= nest->nj_map; } } |