diff options
Diffstat (limited to 'sql')
| -rw-r--r-- | sql/sql_select.cc | 100 |
1 files changed, 61 insertions, 39 deletions
diff --git a/sql/sql_select.cc b/sql/sql_select.cc index 5912f3021dc..8ee1fbca6a5 100644 --- a/sql/sql_select.cc +++ b/sql/sql_select.cc @@ -1,4 +1,4 @@ -/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB +/* Copyright (C) 2000-2003 MySQL AB & MySQL Finland AB & TCX DataKonsult AB This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -1256,7 +1256,6 @@ make_join_statistics(JOIN *join,TABLE_LIST *tables,COND *conds, table_map found_const_table_map,all_table_map; TABLE **table_vector; JOIN_TAB *stat,*stat_end,*s,**stat_ref; - SQL_SELECT *select; KEYUSE *keyuse,*start_keyuse; table_map outer_join=0; JOIN_TAB *stat_vector[MAX_TABLES+1]; @@ -1268,7 +1267,6 @@ make_join_statistics(JOIN *join,TABLE_LIST *tables,COND *conds, table_vector=(TABLE**) join->thd->alloc(sizeof(TABLE*)*(table_count*2)); if (!stat || !stat_ref || !table_vector) DBUG_RETURN(1); // Eom /* purecov: inspected */ - select=0; join->best_ref=stat_vector; @@ -1452,7 +1450,7 @@ make_join_statistics(JOIN *join,TABLE_LIST *tables,COND *conds, { // Found everything for ref. int tmp; ref_changed = 1; - s->type=JT_CONST; + s->type= JT_CONST; join->const_table_map|=table->map; set_position(join,const_count++,s,start_keyuse); if (create_ref_for_key(join, s, start_keyuse, @@ -1503,23 +1501,44 @@ make_join_statistics(JOIN *join,TABLE_LIST *tables,COND *conds, if (s->const_keys) { ha_rows records; - if (!select) - select=make_select(s->table, found_const_table_map, - found_const_table_map, - and_conds(conds,s->on_expr),&error); - records=get_quick_record_count(select,s->table, s->const_keys, - join->row_limit); + SQL_SELECT *select; + select= make_select(s->table, found_const_table_map, + found_const_table_map, + s->on_expr ? s->on_expr : conds, + &error); + records= get_quick_record_count(select,s->table, s->const_keys, + join->row_limit); s->quick=select->quick; s->needed_reg=select->needed_reg; select->quick=0; + if (records == 0 && s->table->reginfo.impossible_range) + { + /* + Impossible WHERE or ON expression + In case of ON, we mark that the we match one empty NULL row. + In case of WHERE, don't set found_const_table_map to get the + caller to abort with a zero row result. + */ + join->const_table_map|= s->table->map; + set_position(join,const_count++,s,(KEYUSE*) 0); + s->type= JT_CONST; + if (s->on_expr) + { + /* Generate empty row */ + s->info= "Impossible ON condition"; + found_const_table_map|= s->table->map; + s->type= JT_CONST; + mark_as_null_row(s->table); // All fields are NULL + } + } if (records != HA_POS_ERROR) { s->found_records=records; s->read_time= (ha_rows) (s->quick ? s->quick->read_time : 0.0); } + delete select; } } - delete select; /* Find best combination and return it */ join->join_tab=stat; @@ -2615,7 +2634,7 @@ static bool create_ref_for_key(JOIN *join, JOIN_TAB *j, KEYUSE *org_keyuse, keyparts != keyinfo->key_parts) j->type=JT_REF; /* Must read with repeat */ else if (ref_key == j->ref.key_copy) - { /* Should never be reached */ + { /* This happen if we are using a constant expression in the ON part of an LEFT JOIN. @@ -7729,37 +7748,40 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order, if (tab->info) item_list.push_back(new Item_string(tab->info,strlen(tab->info), default_charset_info)); - else if (tab->select) + else { - if (tab->use_quick == 2) + if (tab->select) { - sprintf(buff_ptr,"; Range checked for each record (index map: %u)", - tab->keys); - buff_ptr=strend(buff_ptr); + if (tab->use_quick == 2) + { + sprintf(buff_ptr,"; Range checked for each record (index map: %u)", + tab->keys); + buff_ptr=strend(buff_ptr); + } + else + buff_ptr=strmov(buff_ptr,"; Using where"); } - else - buff_ptr=strmov(buff_ptr,"; Using where"); - } - if (key_read) - buff_ptr= strmov(buff_ptr,"; Using index"); - if (table->reginfo.not_exists_optimize) - buff_ptr= strmov(buff_ptr,"; Not exists"); - if (need_tmp_table) - { - need_tmp_table=0; - buff_ptr= strmov(buff_ptr,"; Using temporary"); - } - if (need_order) - { - need_order=0; - buff_ptr= strmov(buff_ptr,"; Using filesort"); + if (key_read) + buff_ptr= strmov(buff_ptr,"; Using index"); + if (table->reginfo.not_exists_optimize) + buff_ptr= strmov(buff_ptr,"; Not exists"); + if (need_tmp_table) + { + need_tmp_table=0; + buff_ptr= strmov(buff_ptr,"; Using temporary"); + } + if (need_order) + { + need_order=0; + buff_ptr= strmov(buff_ptr,"; Using filesort"); + } + if (distinct & test_all_bits(used_tables,thd->used_tables)) + buff_ptr= strmov(buff_ptr,"; Distinct"); + if (buff_ptr == buff) + buff_ptr+= 2; // Skip inital "; " + item_list.push_back(new Item_string(buff+2,(uint) (buff_ptr - buff)-2, + default_charset_info)); } - if (distinct & test_all_bits(used_tables,thd->used_tables)) - buff_ptr= strmov(buff_ptr,"; Distinct"); - if (buff_ptr == buff) - buff_ptr+= 2; // Skip inital "; " - item_list.push_back(new Item_string(buff+2,(uint) (buff_ptr - buff)-2, - default_charset_info)); // For next iteration used_tables|=table->map; if (result->send_data(item_list)) |