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Mark constant 'null_tables' with table->const_table=1

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This was done to make thing consistent. It gives the additional benefit
that EXPLAIN EXTENDED now treat null_tables like constant's and replaces
columns with NULL, in a similar way that it replaces columns with constants
for constant tables.

- Null tables are tables where all columns are always NULL. The most common
  NULL TABLE is a table used in a LEFT_JOIN that is never true.
- All result changes comes from replacing columns with NULL for null_tables.
- "Impossible where" is now also shows constants for const columns.
- Removed duplicated s->type= JT_CONST
- Reset found_const_table_map when JOIN is created (safety fix)
This commit is contained in:
Monty
2017-11-30 17:01:23 +02:00
parent ddac2d7a1e
commit c65911ac46
10 changed files with 15 additions and 11 deletions
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2
mysql-test/r/range.result
View File

@ -2284,7 +2284,7 @@ explain extended select * from t2 where (b > 25 and b < 15) or (a>55 and a<44);
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1003 select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`c` AS `c` from `test`.`t2` where 0
Note 1003 select 44 AS `a`,15 AS `b`,NULL AS `c` from `test`.`t2` where 0
drop table t1,t2;
#
# Start of 10.1 tests

2
mysql-test/r/range_mrr_icp.result
View File

@ -2286,7 +2286,7 @@ explain extended select * from t2 where (b > 25 and b < 15) or (a>55 and a<44);
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1003 select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t2`.`c` AS `c` from `test`.`t2` where 0
Note 1003 select 44 AS `a`,15 AS `b`,NULL AS `c` from `test`.`t2` where 0
drop table t1,t2;
#
# Start of 10.1 tests

2
mysql-test/r/select.result
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@ -5482,7 +5482,7 @@ WHERE i1 = i2 AND ( FALSE OR ( j1 > 27 AND j1 < 100 OR j1 <= 3 ) AND j1 = i2 );
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1003 select 1 AS `i1`,8 AS `j1`,`test`.`t2`.`i2` AS `i2` from `test`.`t2` where 0
Note 1003 select 1 AS `i1`,8 AS `j1`,NULL AS `i2` from `test`.`t2` where 0
SELECT * FROM t1, t2
WHERE i1 = i2 AND ( FALSE OR ( j1 > 27 AND j1 < 100 OR j1 <= 3 ) AND j1 = i2 );
i1 j1 i2

2
mysql-test/r/select_jcl6.result
View File

@ -5493,7 +5493,7 @@ WHERE i1 = i2 AND ( FALSE OR ( j1 > 27 AND j1 < 100 OR j1 <= 3 ) AND j1 = i2 );
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1003 select 1 AS `i1`,8 AS `j1`,`test`.`t2`.`i2` AS `i2` from `test`.`t2` where 0
Note 1003 select 1 AS `i1`,8 AS `j1`,NULL AS `i2` from `test`.`t2` where 0
SELECT * FROM t1, t2
WHERE i1 = i2 AND ( FALSE OR ( j1 > 27 AND j1 < 100 OR j1 <= 3 ) AND j1 = i2 );
i1 j1 i2

2
mysql-test/r/select_pkeycache.result
View File

@ -5482,7 +5482,7 @@ WHERE i1 = i2 AND ( FALSE OR ( j1 > 27 AND j1 < 100 OR j1 <= 3 ) AND j1 = i2 );
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1003 select 1 AS `i1`,8 AS `j1`,`test`.`t2`.`i2` AS `i2` from `test`.`t2` where 0
Note 1003 select 1 AS `i1`,8 AS `j1`,NULL AS `i2` from `test`.`t2` where 0
SELECT * FROM t1, t2
WHERE i1 = i2 AND ( FALSE OR ( j1 > 27 AND j1 < 100 OR j1 <= 3 ) AND j1 = i2 );
i1 j1 i2

4
mysql-test/r/selectivity.result
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@ -784,7 +784,7 @@ select * from t1 where a < 1 and a > 7;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1003 select `test`.`t1`.`a` AS `a` from `test`.`t1` where 0
Note 1003 select 7 AS `a` from `test`.`t1` where 0
select * from t1 where a < 1 and a > 7;
a
drop table t1;
@ -1508,7 +1508,7 @@ select * from t2 where col1 < 'b' and col1 > 'd';
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1003 select `test`.`t2`.`col1` AS `col1` from `test`.`t2` where 0
Note 1003 select 'd' AS `col1` from `test`.`t2` where 0
drop table t1,t2;
set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
set use_stat_tables=@save_use_stat_tables;

4
mysql-test/r/selectivity_innodb.result
View File

@ -791,7 +791,7 @@ select * from t1 where a < 1 and a > 7;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1003 select `test`.`t1`.`a` AS `a` from `test`.`t1` where 0
Note 1003 select 7 AS `a` from `test`.`t1` where 0
select * from t1 where a < 1 and a > 7;
a
drop table t1;
@ -1518,7 +1518,7 @@ select * from t2 where col1 < 'b' and col1 > 'd';
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1003 select `test`.`t2`.`col1` AS `col1` from `test`.`t2` where 0
Note 1003 select 'd' AS `col1` from `test`.`t2` where 0
drop table t1,t2;
set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
set use_stat_tables=@save_use_stat_tables;

1
sql/opt_table_elimination.cc
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@ -1810,6 +1810,7 @@ static void mark_as_eliminated(JOIN *join, TABLE_LIST *tbl)
{
DBUG_PRINT("info", ("Eliminated table %s", table->alias.c_ptr()));
tab->type= JT_CONST;
tab->table->const_table= 1;
join->eliminated_tables |= table->map;
join->const_table_map|= table->map;
set_position(join, join->const_tables++, tab, (KEYUSE*)0);

5
sql/sql_select.cc
View File

@ -4198,6 +4198,7 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
keyuse->val->is_null() && keyuse->null_rejecting)
{
s->type= JT_CONST;
s->table->const_table= 1;
mark_as_null_row(table);
found_const_table_map|= table->map;
join->const_table_map|= table->map;
@ -4303,6 +4304,7 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
s->type= JT_CONST;
join->const_table_map|=table->map;
set_position(join,const_count++,s,start_keyuse);
/* create_ref_for_key will set s->table->const_table */
if (create_ref_for_key(join, s, start_keyuse, FALSE,
found_const_table_map))
goto error;
@ -4508,12 +4510,12 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
join->const_table_map|= s->table->map;
set_position(join,const_count++,s,(KEYUSE*) 0);
s->type= JT_CONST;
s->table->const_table= 1;
if (*s->on_expr_ref)
{
/* Generate empty row */
s->info= ET_IMPOSSIBLE_ON_CONDITION;
found_const_table_map|= s->table->map;
s->type= JT_CONST;
mark_as_null_row(s->table); // All fields are NULL
}
}
@ -19533,6 +19535,7 @@ join_read_system(JOIN_TAB *tab)
{
if (error != HA_ERR_END_OF_FILE)
return report_error(table, error);
table->const_table= 1;
mark_as_null_row(tab->table);
empty_record(table); // Make empty record
return -1;

2
sql/sql_select.h
View File

@ -1436,7 +1436,7 @@ public:
table_count= 0;
top_join_tab_count= 0;
const_tables= 0;
const_table_map= 0;
const_table_map= found_const_table_map= 0;
aggr_tables= 0;
eliminated_tables= 0;
join_list= 0;