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mirror of https://github.com/MariaDB/server.git synced 2025-07-27 18:02:13 +03:00

Merge mysql.com:/home/psergey/mysql-5.0-bug14026-r2

into mysql.com:/home/psergey/mysql-5.0-oct03-push
This commit is contained in:
sergefp@mysql.com
2005-11-03 16:21:21 +03:00
9 changed files with 445 additions and 17 deletions

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_bitmap_for_nested_joins(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);
@ -520,12 +526,14 @@ 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()
{
@ -588,6 +596,7 @@ JOIN::optimize()
/* Convert all outer joins to inner joins if possible */
conds= simplify_joins(this, join_list, conds, TRUE);
build_bitmap_for_nested_joins(join_list, 0);
sel->prep_where= conds ? conds->copy_andor_structure(thd) : 0;
@ -700,7 +709,8 @@ JOIN::optimize()
DBUG_PRINT("error",("Error: make_select() failed"));
DBUG_RETURN(1);
}
reset_nj_counters(join_list);
make_outerjoin_info(this);
/*
@ -1968,14 +1978,19 @@ 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;
@ -3549,6 +3564,8 @@ 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
@ -4029,7 +4046,9 @@ 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;
@ -4045,6 +4064,7 @@ 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;
}
@ -4073,6 +4093,7 @@ 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;
}
}
@ -4107,9 +4128,11 @@ 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;
@ -4154,7 +4177,8 @@ 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;
@ -4492,10 +4516,10 @@ 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 ||
@ -4516,6 +4540,7 @@ 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
}
@ -5101,7 +5126,7 @@ 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)
{
@ -7262,11 +7287,11 @@ 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
@ -7423,7 +7448,257 @@ 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_bitmap_for_nested_joins()
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 "confluent" ones - those that
embed only one element) a bit in nested_join_map.
NOTE
This function is called after simplify_joins(), when there are no
redundant nested joins, #non_confluent_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_bitmap_for_nested_joins(List<TABLE_LIST> *join_list,
uint first_unused)
{
List_iterator<TABLE_LIST> li(*join_list);
TABLE_LIST *table;
DBUG_ENTER("build_bitmap_for_nested_joins");
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 the child
is an underlying table). We don't assign bits to such nested join
structures 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_bitmap_for_nested_joins(&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.
IMPLEMENTATION
LIMITATIONS ON JOIN ORDER
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.
HOW IT IS IMPLEMENTED
The limitations on join order can be rephrased as follows: for valid
join order one must be able to:
1. write down the used tables in the join order on one line.
2. for each nested join, put one '(' and one ')' on the said line
3. write "LEFT JOIN" and "ON (...)" where appropriate
4. get a query equivalent to the query we're trying to execute.
Calls to check_interleaving_with_nj() are equivalent to writing the
above described line from left to right.
A single check_interleaving_with_nj(A,B) call is equivalent to writing
table B and appropriate brackets on condition that table A and
appropriate brackets is the last what was written. Graphically the
transition is as follows:
+---- current position
|
... last_tab ))) | ( next_tab ) )..) | ...
X Y Z |
+- need to move to this
position.
Notes about the position:
The caller guarantees that there is no more then one X-bracket by
checking "!(remaining_tables & s->dependent)" before calling this
function. X-bracket may have a pair in Y-bracket.
When "writing" we store/update this auxilary info about the current
position:
1. join->cur_embedding_map - bitmap of pairs of brackets (aka nested
joins) we've opened but didn't close.
2. {each NESTED_JOIN structure not simplified away}->counter - number
of this nested join's children that have already been added to to
the partial join order.
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_tab, JOIN_TAB *next_tab)
{
TABLE_LIST *next_emb= next_tab->table->pos_in_table_list->embedding;
JOIN *join= last_tab->join;
if (join->cur_embedding_map & ~next_tab->embedding_map)
{
/*
next_tab is outside of the "pair of brackets" we're currently in.
Cannot add it.
*/
return TRUE;
}
/*
Do update counters for "pairs of brackets" that we've left (marked as
X,Y,Z in the above picture)
*/
for (;next_emb; next_emb= next_emb->embedding)
{
next_emb->nested_join->counter++;
if (next_emb->nested_join->counter == 1)
{
/*
next_emb is the first table inside a nested join we've "entered". In
the picture above, we're looking at the 'X' bracket. Don't exit yet as
X bracket might have Y pair bracket.
*/
join->cur_embedding_map |= next_emb->nested_join->nj_map;
}
if (next_emb->nested_join->join_list.elements !=
next_emb->nested_join->counter)
break;
/*
We're currently at Y or Z-bracket as depicted in the above picture.
Mark that we've left it and continue walking up the brackets hierarchy.
*/
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,