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BUG#13126: When choosing join order for join with nested joins, don't produce join

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orders that cannot be handled by the executioner.


mysql-test/r/bigint.result:
  Added mssing "drop table if exists"
mysql-test/r/join_nested.result:
  Testcase for BUG#13126
mysql-test/t/bigint.test:
  Added mssing "drop table if exists"
mysql-test/t/join_nested.test:
  Testcase for BUG#13126
sql/mysql_priv.h:
  BUG#13126: Added nested_join_map type.
sql/sql_prepare.cc:
  BUG#13126: Don't set NESTED_JOIN::counter to 0 here as it is reset in other place now.
sql/sql_select.cc:
  BUG#13126: When choosing join order for join with nested joins, don't produce join orders
  that the executioner cannot handle. The work is done by check_interleaving_with_nj() and 
  restore_prev_nj_state() functions that are used from the join optimizer to avoid building
  invalid join orders.
sql/sql_select.h:
  BUG#13126: Added JOIN_TAB::embedding_map and JOIN::cur_embedding_map.
sql/table.h:
  BUG#13126: In NESTED_JOIN: added nj_map, added comment about where counter is used.
This commit is contained in:
unknown 2005-10-25 19:28:27 +04:00
parent 11541107b8
commit 2b7f5a45e9
9 changed files with 397 additions and 17 deletions
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2
mysql-test/r/bigint.result
View file

@ -1,4 +1,4 @@
drop table if exists t1;
drop table if exists t1, t2;
select 0,256,00000000000000065536,2147483647,-2147483648,2147483648,+4294967296;
0 256 00000000000000065536 2147483647 -2147483648 2147483648 4294967296
0 256 65536 2147483647 -2147483648 2147483648 4294967296

64
mysql-test/r/join_nested.result
View file

@ -1403,3 +1403,67 @@ SELECT v2.x FROM v2 JOIN t2 ON e=b JOIN t3 ON e=c JOIN t4 USING(d);
ERROR 42S22: Unknown column 'v2.x' in 'field list'
DROP VIEW v1, v2;
DROP TABLE t1, t2, t3, t4, t5, t6;
create table t1 (id1 int(11) not null);
insert into t1 values (1),(2);
create table t2 (id2 int(11) not null);
insert into t2 values (1),(2),(3),(4);
create table t3 (id3 char(16) not null);
insert into t3 values ('100');
create table t4 (id2 int(11) not null, id3 char(16));
create table t5 (id1 int(11) not null, key (id1));
insert into t5 values (1),(2),(1);
create view v1 as
select t4.id3 from t4 join t2 on t4.id2 = t2.id2;
select t1.id1 from t1 inner join (t3 left join v1 on t3.id3 = v1.id3);
id1
1
2
drop view v1;
drop table t1, t2, t3, t4, t5;
create table t0 (a int);
insert into t0 values (0),(1),(2),(3);
create table t1(a int);
insert into t1 select A.a + 10*(B.a) from t0 A, t0 B;
create table t2 (a int, b int);
insert into t2 values (1,1), (2,2), (3,3);
create table t3(a int, b int, filler char(200), key(a));
insert into t3 select a,a,'filler' from t1;
insert into t3 select a,a,'filler' from t1;
create table t4 like t3;
insert into t4 select * from t3;
insert into t4 select * from t3;
create table t5 like t4;
insert into t5 select * from t4;
insert into t5 select * from t4;
create table t6 like t5;
insert into t6 select * from t5;
insert into t6 select * from t5;
create table t7 like t6;
insert into t7 select * from t6;
insert into t7 select * from t6;
explain select * from t4 join
t2 left join (t3 join t5 on t5.a=t3.b) on t3.a=t2.b where t4.a<=>t3.b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL X
1 SIMPLE t3 ref a a 5 test.t2.b X
1 SIMPLE t5 ref a a 5 test.t3.b X
1 SIMPLE t4 ref a a 5 test.t3.b X Using where
explain select * from (t4 join t6 on t6.a=t4.b) right join t3 on t4.a=t3.b
join t2 left join (t5 join t7 on t7.a=t5.b) on t5.a=t2.b where t3.a<=>t2.b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL X
1 SIMPLE t3 ref a a 5 test.t2.b X Using where
1 SIMPLE t4 ref a a 5 test.t3.b X
1 SIMPLE t6 ref a a 5 test.t4.b X
1 SIMPLE t5 ref a a 5 test.t2.b X
1 SIMPLE t7 ref a a 5 test.t5.b X
explain select * from t2 left join
(t3 left join (t4 join t6 on t6.a=t4.b) on t4.a=t3.b
join t5 on t5.a=t3.b) on t3.a=t2.b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL X
1 SIMPLE t3 ref a a 5 test.t2.b X
1 SIMPLE t4 ref a a 5 test.t3.b X
1 SIMPLE t6 ref a a 5 test.t4.b X
1 SIMPLE t5 ref a a 5 test.t3.b X
drop table t0, t1, t2, t4, t5, t6;

2
mysql-test/t/bigint.test
View file

@ -2,7 +2,7 @@
# Initialize
--disable_warnings
drop table if exists t1;
drop table if exists t1, t2;
--enable_warnings
#

68
mysql-test/t/join_nested.test
View file

@ -832,3 +832,71 @@ SELECT v2.x FROM v2 JOIN t2 ON e=b JOIN t3 ON e=c JOIN t4 USING(d);
DROP VIEW v1, v2;
DROP TABLE t1, t2, t3, t4, t5, t6;
#
# BUG#13126 -test case from bug report
#
create table t1 (id1 int(11) not null);
insert into t1 values (1),(2);
create table t2 (id2 int(11) not null);
insert into t2 values (1),(2),(3),(4);
create table t3 (id3 char(16) not null);
insert into t3 values ('100');
create table t4 (id2 int(11) not null, id3 char(16));
create table t5 (id1 int(11) not null, key (id1));
insert into t5 values (1),(2),(1);
create view v1 as
select t4.id3 from t4 join t2 on t4.id2 = t2.id2;
select t1.id1 from t1 inner join (t3 left join v1 on t3.id3 = v1.id3);
drop view v1;
drop table t1, t2, t3, t4, t5;
create table t0 (a int);
insert into t0 values (0),(1),(2),(3);
create table t1(a int);
insert into t1 select A.a + 10*(B.a) from t0 A, t0 B;
create table t2 (a int, b int);
insert into t2 values (1,1), (2,2), (3,3);
create table t3(a int, b int, filler char(200), key(a));
insert into t3 select a,a,'filler' from t1;
insert into t3 select a,a,'filler' from t1;
create table t4 like t3;
insert into t4 select * from t3;
insert into t4 select * from t3;
create table t5 like t4;
insert into t5 select * from t4;
insert into t5 select * from t4;
create table t6 like t5;
insert into t6 select * from t5;
insert into t6 select * from t5;
create table t7 like t6;
insert into t7 select * from t6;
insert into t7 select * from t6;
--replace_column 9 X
explain select * from t4 join
t2 left join (t3 join t5 on t5.a=t3.b) on t3.a=t2.b where t4.a<=>t3.b;
--replace_column 9 X
explain select * from (t4 join t6 on t6.a=t4.b) right join t3 on t4.a=t3.b
join t2 left join (t5 join t7 on t7.a=t5.b) on t5.a=t2.b where t3.a<=>t2.b;
--replace_column 9 X
explain select * from t2 left join
(t3 left join (t4 join t6 on t6.a=t4.b) on t4.a=t3.b
join t5 on t5.a=t3.b) on t3.a=t2.b;
drop table t0, t1, t2, t4, t5, t6;

5
sql/mysql_priv.h
View file

@ -44,6 +44,11 @@
typedef ulonglong table_map; /* Used for table bits in join */
typedef Bitmap<64> key_map; /* Used for finding keys */
typedef ulong key_part_map; /* Used for finding key parts */
/*
Used for nested join bits within a scope of a join (applicable to non-unary
nested joins that have not been simplified away)
*/
typedef ulonglong nested_join_map;
/* query_id */
typedef ulonglong query_id_t;

2
sql/sql_prepare.cc
View file

@ -2105,8 +2105,6 @@ void reinit_stmt_before_use(THD *thd, LEX *lex)
were closed in the end of previous prepare or execute call.
*/
tables->table= 0;
if (tables->nested_join)
tables->nested_join->counter= 0;
if (tables->prep_on_expr)
{

250
sql/sql_select.cc
View file

@ -98,6 +98,12 @@ static COND* substitute_for_best_equal_field(COND *cond,
void *table_join_idx);
static COND *simplify_joins(JOIN *join, List<TABLE_LIST> *join_list,
COND *conds, bool top);
static bool check_interleaving_with_nj(JOIN_TAB *last, JOIN_TAB *next);
static void restore_prev_nj_state(JOIN_TAB *last);
static void reset_nj_counters(List<TABLE_LIST> *join_list);
static uint build_nj_bitmap_for_tables(JOIN *join, List<TABLE_LIST> *join_list,
uint first_unused);
static COND *optimize_cond(JOIN *join, COND *conds,
List<TABLE_LIST> *join_list,
Item::cond_result *cond_value);
@ -522,12 +528,14 @@ bool JOIN::test_in_subselect(Item **where)
return 0;
}
/*
global select optimisation.
return 0 - success
1 - error
error code saved in field 'error'
*/
int
JOIN::optimize()
{
@ -587,6 +595,7 @@ JOIN::optimize()
/* Convert all outer joins to inner joins if possible */
conds= simplify_joins(this, join_list, conds, TRUE);
build_nj_bitmap_for_tables(this, join_list, 0);
sel->prep_where= conds ? conds->copy_andor_structure(thd) : 0;
@ -699,7 +708,8 @@ JOIN::optimize()
DBUG_PRINT("error",("Error: make_select() failed"));
DBUG_RETURN(1);
}
reset_nj_counters(join_list);
make_outerjoin_info(this);
/*
@ -1961,14 +1971,19 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables, COND *conds,
continue;
}
outer_join|= table->map;
s->embedding_map= 0;
for (;embedding; embedding= embedding->embedding)
s->embedding_map|= embedding->nested_join->nj_map;
continue;
}
if (embedding)
{
/* s belongs to a nested join, maybe to several embedded joins */
s->embedding_map= 0;
do
{
NESTED_JOIN *nested_join= embedding->nested_join;
s->embedding_map|=nested_join->nj_map;
s->dependent|= embedding->dep_tables;
embedding= embedding->embedding;
outer_join|= nested_join->used_tables;
@ -3542,6 +3557,8 @@ choose_plan(JOIN *join, table_map join_tables)
bool straight_join= join->select_options & SELECT_STRAIGHT_JOIN;
DBUG_ENTER("choose_plan");
join->cur_embedding_map= 0;
reset_nj_counters(join->join_list);
/*
if (SELECT_STRAIGHT_JOIN option is set)
reorder tables so dependent tables come after tables they depend
@ -4022,7 +4039,9 @@ best_extension_by_limited_search(JOIN *join,
for (JOIN_TAB **pos= join->best_ref + idx ; (s= *pos) ; pos++)
{
table_map real_table_bit= s->table->map;
if ((remaining_tables & real_table_bit) && !(remaining_tables & s->dependent))
if ((remaining_tables & real_table_bit) &&
!(remaining_tables & s->dependent) &&
(!idx || !check_interleaving_with_nj(join->positions[idx-1].table, s)))
{
double current_record_count, current_read_time;
@ -4038,6 +4057,7 @@ best_extension_by_limited_search(JOIN *join,
{
DBUG_EXECUTE("opt", print_plan(join, read_time, record_count, idx,
"prune_by_cost"););
restore_prev_nj_state(s);
continue;
}
@ -4066,6 +4086,7 @@ best_extension_by_limited_search(JOIN *join,
{
DBUG_EXECUTE("opt", print_plan(join, read_time, record_count, idx,
"pruned_by_heuristic"););
restore_prev_nj_state(s);
continue;
}
}
@ -4100,9 +4121,11 @@ best_extension_by_limited_search(JOIN *join,
sizeof(POSITION) * (idx + 1));
join->best_read= current_read_time - 0.001;
}
DBUG_EXECUTE("opt",
print_plan(join, current_read_time, current_record_count, idx, "full_plan"););
DBUG_EXECUTE("opt", print_plan(join, current_read_time,
current_record_count, idx,
"full_plan"););
}
restore_prev_nj_state(s);
}
}
DBUG_VOID_RETURN;
@ -4147,7 +4170,8 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
for (JOIN_TAB **pos=join->best_ref+idx ; (s=*pos) ; pos++)
{
table_map real_table_bit=s->table->map;
if ((rest_tables & real_table_bit) && !(rest_tables & s->dependent))
if ((rest_tables & real_table_bit) && !(rest_tables & s->dependent) &&
(!idx|| !check_interleaving_with_nj(join->positions[idx-1].table, s)))
{
double best,best_time,records;
best=best_time=records=DBL_MAX;
@ -4485,10 +4509,10 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
join->unit->select_limit_cnt >= records)
join->sort_by_table= (TABLE*) 1; // Must use temporary table
/*
/*
Go to the next level only if there hasn't been a better key on
this level! This will cut down the search for a lot simple cases!
*/
*/
double current_record_count=record_count*records;
double current_read_time=read_time+best;
if (best_record_count > current_record_count ||
@ -4509,6 +4533,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
return;
swap_variables(JOIN_TAB*, join->best_ref[idx], *pos);
}
restore_prev_nj_state(s);
if (join->select_options & SELECT_STRAIGHT_JOIN)
break; // Don't test all combinations
}
@ -5094,7 +5119,7 @@ add_found_match_trig_cond(JOIN_TAB *tab, COND *cond, JOIN_TAB *root_tab)
This function can be called only after the execution plan
has been chosen.
*/
static void
make_outerjoin_info(JOIN *join)
{
@ -7255,11 +7280,11 @@ propagate_cond_constants(THD *thd, I_List<COND_CMP> *save_list,
ascent all attributes are calculated, all outer joins that can be
converted are replaced and then all unnecessary braces are removed.
As join list contains join tables in the reverse order sequential
elimination of outer joins does not requite extra recursive calls.
elimination of outer joins does not require extra recursive calls.
EXAMPLES
Here is an example of a join query with invalid cross references:
SELECT * FROM t1 LEFT JOIN t2 ON t2.a=t3.a LEFT JOIN ON t3.b=t1.b
SELECT * FROM t1 LEFT JOIN t2 ON t2.a=t3.a LEFT JOIN t3 ON t3.b=t1.b
RETURN VALUE
The new condition, if success
@ -7416,7 +7441,210 @@ simplify_joins(JOIN *join, List<TABLE_LIST> *join_list, COND *conds, bool top)
}
DBUG_RETURN(conds);
}
/*
Assign each nested join structure a bit in nested_join_map
SYNOPSIS
build_nj_bitmap_for_tables()
join Join being processed
join_list List of tables
first_unused Number of first unused bit in nested_join_map before the
call
DESCRIPTION
Assign each nested join structure (except for unary nested joins, see
below) a bit in nested_join_map.
NOTE
This function is called after simplify_joins(), when there are no
redundant nested joins, #non_unary_nested_joins <= #tables_in_join so we
will not run out of bits in nested_join_map.
RETURN
First unused bit in nested_join_map after the call.
*/
static uint build_nj_bitmap_for_tables(JOIN *join, List<TABLE_LIST> *join_list,
uint first_unused)
{
List_iterator<TABLE_LIST> li(*join_list);
TABLE_LIST *table;
DBUG_ENTER("build_nj_bitmap_for_tables");
while ((table= li++))
{
NESTED_JOIN *nested_join;
if ((nested_join= table->nested_join))
{
/*
It is guaranteed by simplify_joins() function that a nested join
that has only one child represents a single table VIEW (and a child
is an underlying table). We don't assign a bit to the nested join
because
1. it is redundant (a "sequence" of one table cannot be interleaved
with anything)
2. we could run out bits in nested_join_map otherwise.
*/
if (nested_join->join_list.elements != 1)
{
nested_join->nj_map= 1 << first_unused++;
first_unused= build_nj_bitmap_for_tables(join, &nested_join->join_list,
first_unused);
}
}
}
DBUG_RETURN(first_unused);
}
/*
Set NESTED_JOIN::counter=0 in all nested joins in passed list
SYNOPSIS
reset_nj_counters()
join_list List of nested joins to process. It may also contain base
tables which will be ignored.
DESCRIPTION
Recursively set NESTED_JOIN::counter=0 for all nested joins contained in
the passed join_list.
*/
static void reset_nj_counters(List<TABLE_LIST> *join_list)
{
List_iterator<TABLE_LIST> li(*join_list);
TABLE_LIST *table;
DBUG_ENTER("reset_nj_counters");
while ((table= li++))
{
NESTED_JOIN *nested_join;
if ((nested_join= table->nested_join))
{
nested_join->counter= 0;
reset_nj_counters(&nested_join->join_list);
}
}
DBUG_VOID_RETURN;
}
/*
Check interleaving with an inner tables of an outer join for extension table
SYNOPSIS
check_interleaving_with_nj()
join Join being processed
last_tab Last table in current partial join order (this function is
not called for empty partial join orders)
next_tab Table we're going to extend the current partial join with
DESCRIPTION
Check if table next_tab can be added to current partial join order, and
if yes, record that it has been added.
The function assumes that both current partial join order and its
extension with next_tab are valid wrt table dependencies.
NOTE
The nested joins aspect of information about current partial join order is
stored in join->cur_embedding_map and
{each_join_table}->pos_in_table_list (->embedding)+ ->nested_join->counter
Joins optimizer calls check_interleaving_with_nj() and
restore_prev_nj_state() to update this info and avoid constructing invalid
join orders. There is no need for any initialization of
{each_join_table}->...->counter before the join optimizer run.
IMPLEMENTATION
The nested [outer] joins executioner algorithm imposes these limitations
on join order:
1. "Outer tables first" - any "outer" table must be before any
corresponding "inner" table.
2. "No interleaving" - tables inside a nested join must form a continuous
sequence in join order (i.e. the sequence must not be interrupted by
tables that are outside of this nested join).
#1 is checked elsewhere, this function checks #2 provided that #1 has been
already checked.
WHY NEED NON-INTERLEAVING
Consider an example:
select * from t0 join t1 left join (t2 join t3) on cond1
The join order "t1 t2 t0 t3" is invalid:
table t0 is outside of the nested join, so WHERE condition for t0 is
attached directly to t0 (without triggers, and it may be used to access
t0). Applying WHERE(t0) to (t2,t0,t3) record is invalid as we may miss
combinations of (t1, t2, t3) that satisfy condition cond1, and produce a
null-complemented (t1, t2.NULLs, t3.NULLs) row, which should not have
been produced.
If table t0 is not between t2 and t3, the problem doesn't exist:
* If t0 is located after (t2,t3), WHERE(t0) is applied after nested join
processing has finished.
* If t0 is located before (t2,t3), predicates like WHERE_cond(t0, t2) are
wrapped into condition triggers, which takes care of correct nested
join processing.
RETURN
FALSE Join order extended, nested joins info about current join order
(see NOTE section) updated.
TRUE Requested join order extension not allowed.
*/
static bool check_interleaving_with_nj(JOIN_TAB *last, JOIN_TAB *next)
{
TABLE_LIST *next_emb= next->table->pos_in_table_list->embedding;
JOIN *join= last->join;
if (join->cur_embedding_map & ~next->embedding_map)
return TRUE;
for (;next_emb; next_emb= next_emb->embedding)
{
next_emb->nested_join->counter++;
if (next_emb->nested_join->counter == 1)
{
/* next_emb is a first table inside a nested join */
join->cur_embedding_map |= next_emb->nested_join->nj_map;
}
if (next_emb->nested_join->join_list.elements !=
next_emb->nested_join->counter)
break;
join->cur_embedding_map &= ~next_emb->nested_join->nj_map;
}
return FALSE;
}
/*
Nested joins perspective: Remove the last table from the join order
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
check_interleaving_with_nj has not been called)
*/
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 && !(--last_emb->nested_join->counter))
{
join->cur_embedding_map &= last_emb->nested_join->nj_map;
last_emb= last_emb->embedding;
}
}
static COND *
optimize_cond(JOIN *join, COND *conds, List<TABLE_LIST> *join_list,

11
sql/sql_select.h
View file

@ -136,7 +136,9 @@ typedef struct st_join_table {
TABLE_REF ref;
JOIN_CACHE cache;
JOIN *join;
/* Bitmap of nested joins this table is part of */
nested_join_map embedding_map;
void cleanup();
} JOIN_TAB;
@ -193,6 +195,13 @@ class JOIN :public Sql_alloc
*/
ha_rows fetch_limit;
POSITION positions[MAX_TABLES+1],best_positions[MAX_TABLES+1];
/*
Bitmap of nested joins embedding the position at the end of the current
partial join (valid only during join optimizer run).
*/
nested_join_map cur_embedding_map;
double best_read;
List<Item> *fields;
List<Cached_item> group_fields, group_fields_cache;

10
sql/table.h
View file

@ -757,7 +757,15 @@ typedef struct st_nested_join
table_map used_tables; /* bitmap of tables in the nested join */
table_map not_null_tables; /* tables that rejects nulls */
struct st_join_table *first_nested;/* the first nested table in the plan */
uint counter; /* to count tables in the nested join */
/*
Used to count tables in the nested join in 2 isolated places:
1. In make_outerjoin_info().
2. check_interleaving_with_nj/restore_prev_nj_state (these are called
by the join optimizer.
Before each use the counters are zeroed by reset_nj_counters.
*/
uint counter;
nested_join_map nj_map; /* Bit used to identify this nested join*/
} NESTED_JOIN;