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Commit 6fba16ea authored by kostja@oak.local's avatar kostja@oak.local
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Applied Monty corrections to the FULL SCAN 

optimiser bug patch.
parent f13d9312
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Showing with 43 additions and 32 deletions
mysql-test/r/distinct.result
View file @ 6fba16ea
......@@ -173,9 +173,9 @@ INSERT INTO t2 values (1),(2),(3);
INSERT INTO t3 VALUES (1,'1'),(2,'2'),(1,'1'),(2,'2');
explain SELECT distinct t3.a FROM t3,t2,t1 WHERE t3.a=t1.b AND t1.a=t2.a;
table type possible_keys key key_len ref rows Extra
t2 index a a 4 NULL 5 Using index; Using temporary
t1 eq_ref PRIMARY PRIMARY 4 t2.a 1
t3 index a a 5 NULL 5 Using where; Using index
t3 index a a 5 NULL 6 Using index; Using temporary
t2 index a a 4 NULL 5 Using index; Distinct
t1 eq_ref PRIMARY PRIMARY 4 t2.a 1 Using where; Distinct
SELECT distinct t3.a FROM t3,t2,t1 WHERE t3.a=t1.b AND t1.a=t2.a;
a
1
......
mysql-test/r/order_by.result
View file @ 6fba16ea
......@@ -307,17 +307,17 @@ table type possible_keys key key_len ref rows Extra
t1 range a a 9 NULL 8 Using where; Using index
explain select * from t1 where a = 2 and b >0 order by a desc,b desc;
table type possible_keys key key_len ref rows Extra
t1 range a a 9 NULL 4 Using where; Using index
t1 range a a 9 NULL 5 Using where; Using index
explain select * from t1 where a = 2 and b is null order by a desc,b desc;
table type possible_keys key key_len ref rows Extra
t1 ref a a 9 const,const 1 Using where; Using index; Using filesort
explain select * from t1 where a = 2 and (b is null or b > 0) order by a
desc,b desc;
table type possible_keys key key_len ref rows Extra
t1 range a a 9 NULL 5 Using where; Using index
t1 range a a 9 NULL 6 Using where; Using index
explain select * from t1 where a = 2 and b > 0 order by a desc,b desc;
table type possible_keys key key_len ref rows Extra
t1 range a a 9 NULL 4 Using where; Using index
t1 range a a 9 NULL 5 Using where; Using index
explain select * from t1 where a = 2 and b < 2 order by a desc,b desc;
table type possible_keys key key_len ref rows Extra
t1 range a a 9 NULL 2 Using where; Using index
......@@ -466,8 +466,8 @@ t2 eq_ref PRIMARY,uid PRIMARY 4 t1.gid 1
t3 eq_ref PRIMARY PRIMARY 2 t2.uid 1 Using where; Using index
EXPLAIN SELECT t1.gid, t3.uid from t1, t3 where t1.gid = t3.uid order by t1.gid,t3.skr;
table type possible_keys key key_len ref rows Extra
t1 index PRIMARY PRIMARY 4 NULL 6 Using index
t3 eq_ref PRIMARY PRIMARY 2 t1.gid 1 Using where
t3 ALL PRIMARY NULL NULL NULL 6 Using temporary; Using filesort
t1 eq_ref PRIMARY PRIMARY 4 t3.uid 1 Using where; Using index
EXPLAIN SELECT t1.gid, t2.sid, t3.uid from t2, t1, t3 where t2.gid = t1.gid and t2.uid = t3.uid order by t3.uid, t1.gid;
table type possible_keys key key_len ref rows Extra
t1 index PRIMARY PRIMARY 4 NULL 6 Using index; Using temporary; Using filesort
......@@ -475,8 +475,8 @@ t2 eq_ref PRIMARY,uid PRIMARY 4 t1.gid 1
t3 eq_ref PRIMARY PRIMARY 2 t2.uid 1 Using where; Using index
EXPLAIN SELECT t1.gid, t3.uid from t1, t3 where t1.gid = t3.uid order by t3.skr,t1.gid;
table type possible_keys key key_len ref rows Extra
t1 index PRIMARY PRIMARY 4 NULL 6 Using index; Using temporary; Using filesort
t3 eq_ref PRIMARY PRIMARY 2 t1.gid 1 Using where
t3 ALL PRIMARY NULL NULL NULL 6 Using temporary; Using filesort
t1 eq_ref PRIMARY PRIMARY 4 t3.uid 1 Using where; Using index
EXPLAIN SELECT t1.gid, t3.uid from t1, t3 where t1.skr = t3.uid order by t1.gid,t3.skr;
table type possible_keys key key_len ref rows Extra
t1 ALL NULL NULL NULL NULL 6 Using temporary; Using filesort
......
sql/sql_select.cc
View file @ 6fba16ea
......@@ -1898,7 +1898,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
best=best_time=records=DBL_MAX;
KEYUSE *best_key=0;
uint best_max_key_part=0;
my_bool found_constrain= 0;
my_bool found_constraint= 0;
if (s->keyuse)
{ /* Use key if possible */
......@@ -1979,7 +1979,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
}
else
{
found_constrain= 1;
found_constraint= 1;
/*
Check if we found full key
*/
......@@ -2133,12 +2133,28 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
s->table->used_keys && best_key) &&
!(s->table->force_index && best_key))
{ // Check full join
ha_rows rnd_records= s->found_records;
/* Estimate cost of reading table. */
tmp= (double) s->read_time;
tmp= s->table->file->scan_time();
/*
If there is a restriction on the table, assume that 25% of the
rows can be skipped on next part.
This is to force tables that this table depends on before this
table
*/
if (found_constraint)
rnd_records-= rnd_records/4;
if (s->on_expr) // Can't use join cache
{
/* We have to read the whole table for each record */
tmp*= record_count;
tmp= record_count *
/* We have to read the whole table for each record */
(tmp +
/*
And we have to skip rows which does not satisfy join
condition for each record.
*/
(s->records - rnd_records)/(double) TIME_FOR_COMPARE);
}
else
{
......@@ -2146,30 +2162,25 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
tmp*= (1.0 + floor((double) cache_record_length(join,idx) *
record_count /
(double) thd->variables.join_buff_size));
/*
We don't make full cartesian product between rows in the scanned
table and existing records because we skip all rows from the
scanned table, which does not satisfy join condition when
we read the table (see flush_cached_records for details). Here we
take into account cost to read and skip these records.
*/
tmp+= (s->records - rnd_records)/(double) TIME_FOR_COMPARE;
}
/*
We estimate the cost of making full cortesian product between
rows in the scanned table and generated records as
record_count*s->records/TIME_FOR_COMPARE. Taking into account
cost of evaluating WHERE clause for s->found_records is not
necessary because it costs much less than the cost mentioned
above.
We estimate the cost of evaluating WHERE clause for found records
as record_count * rnd_records + TIME_FOR_COMPARE. This cost plus
tmp give us total cost of using TABLE SCAN
*/
if (best == DBL_MAX ||
(tmp + record_count/(double) TIME_FOR_COMPARE*s->records <
(tmp + record_count/(double) TIME_FOR_COMPARE*rnd_records <
best + record_count/(double) TIME_FOR_COMPARE*records))
{
/*
If there is a restriction on the table, assume that 25% of the
rows can be skipped on next part.
This is to force tables that this table depends on before this
table
*/
ha_rows rnd_records= s->found_records;
if (found_constrain)
rnd_records-= rnd_records/4;
/*
If the table has a range (s->quick is set) make_join_select()
will ensure that this will be used
......
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