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Fixed LP bug #675922.

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The bug happened when BKA join algorithm used an incremental buffer
and some of the fields over which access keys were constructed
- were allocated in the previous join buffers
- were non-nullable
- belonged to inner tables of outer joins.
For such fields an offset to the field value in the record is saved
in the postfix of the record, and a zero offset indicates that the value 
is null. Before the key using the field value is constructed the
value is read into the corresponding field of the record buffer and
the null bit is set for the field if the offset is 0. However if
the field is non-nullable the table->null_row must be set to 1
for null values and to 0 for non-null values  to ensure proper reading
of the value from the record buffer.
This commit is contained in:
Igor Babaev 2010-11-19 07:38:02 -08:00
parent 0a3922fca8
commit ae4b5a32a6
3 changed files with 113 additions and 3 deletions
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52
mysql-test/r/join_cache.result
View File

@ -6004,4 +6004,56 @@ a1 a2 b2 a3 b3
SET SESSION optimizer_switch = 'outer_join_with_cache=off';
SET SESSION join_cache_level = DEFAULT;
DROP TABLE t1,t2,t3;
#
# Bug #675922: incremental buffer for BKA with access from previous
# buffers from non-nullable columns whose values may be null
#
CREATE TABLE t1 (a1 varchar(32)) ;
INSERT INTO t1 VALUES ('s'),('k');
CREATE TABLE t2 (a2 int PRIMARY KEY, b2 varchar(32)) ;
INSERT INTO t2 VALUES (7,'s');
CREATE TABLE t3 (a3 int PRIMARY KEY, b3 varchar(32)) ;
INSERT INTO t3 VALUES (7,'s');
CREATE TABLE t4 (a4 int) ;
INSERT INTO t4 VALUES (9);
CREATE TABLE t5(a5 int PRIMARY KEY, b5 int) ;
INSERT INTO t5 VALUES (7,0);
SET SESSION optimizer_switch = 'outer_join_with_cache=on';
SET SESSION join_cache_level = 0;
EXPLAIN
SELECT t4.a4, t5.b5
FROM ((t1 LEFT JOIN (t2 JOIN t3 ON t2.a2 = t3.a3) ON t2.b2 = t1.a1)
LEFT JOIN t4 ON t4.a4 <> 0) LEFT JOIN t5 ON t5.a5 = t2.a2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 2
1 SIMPLE t2 ALL PRIMARY NULL NULL NULL 1 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t2.a2 1 Using index
1 SIMPLE t4 ALL NULL NULL NULL NULL 1 Using where
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t2.a2 1 Using where
SELECT t4.a4, t5.b5
FROM ((t1 LEFT JOIN (t2 JOIN t3 ON t2.a2 = t3.a3) ON t2.b2 = t1.a1)
LEFT JOIN t4 ON t4.a4 <> 0) LEFT JOIN t5 ON t5.a5 = t2.a2;
a4 b5
9 0
9 NULL
SET SESSION join_cache_level = 6;
EXPLAIN
SELECT t4.a4, t5.b5
FROM ((t1 LEFT JOIN (t2 JOIN t3 ON t2.a2 = t3.a3) ON t2.b2 = t1.a1)
LEFT JOIN t4 ON t4.a4 <> 0) LEFT JOIN t5 ON t5.a5 = t2.a2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 2
1 SIMPLE t2 ALL PRIMARY NULL NULL NULL 1 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t2.a2 1 Using index
1 SIMPLE t4 ALL NULL NULL NULL NULL 1 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t2.a2 1 Using where; Using join buffer (incremental, BKA join)
SELECT t4.a4, t5.b5
FROM ((t1 LEFT JOIN (t2 JOIN t3 ON t2.a2 = t3.a3) ON t2.b2 = t1.a1)
LEFT JOIN t4 ON t4.a4 <> 0) LEFT JOIN t5 ON t5.a5 = t2.a2;
a4 b5
9 0
9 NULL
SET SESSION optimizer_switch = 'outer_join_with_cache=off';
SET SESSION join_cache_level = DEFAULT;
DROP TABLE t1,t2,t3,t4,t5;
set @@optimizer_switch=@save_optimizer_switch;

45
mysql-test/t/join_cache.test
View File

@ -2655,5 +2655,50 @@ SET SESSION join_cache_level = DEFAULT;
DROP TABLE t1,t2,t3;
--echo #
--echo # Bug #675922: incremental buffer for BKA with access from previous
--echo # buffers from non-nullable columns whose values may be null
--echo #
CREATE TABLE t1 (a1 varchar(32)) ;
INSERT INTO t1 VALUES ('s'),('k');
CREATE TABLE t2 (a2 int PRIMARY KEY, b2 varchar(32)) ;
INSERT INTO t2 VALUES (7,'s');
CREATE TABLE t3 (a3 int PRIMARY KEY, b3 varchar(32)) ;
INSERT INTO t3 VALUES (7,'s');
CREATE TABLE t4 (a4 int) ;
INSERT INTO t4 VALUES (9);
CREATE TABLE t5(a5 int PRIMARY KEY, b5 int) ;
INSERT INTO t5 VALUES (7,0);
SET SESSION optimizer_switch = 'outer_join_with_cache=on';
SET SESSION join_cache_level = 0;
EXPLAIN
SELECT t4.a4, t5.b5
FROM ((t1 LEFT JOIN (t2 JOIN t3 ON t2.a2 = t3.a3) ON t2.b2 = t1.a1)
LEFT JOIN t4 ON t4.a4 <> 0) LEFT JOIN t5 ON t5.a5 = t2.a2;
SELECT t4.a4, t5.b5
FROM ((t1 LEFT JOIN (t2 JOIN t3 ON t2.a2 = t3.a3) ON t2.b2 = t1.a1)
LEFT JOIN t4 ON t4.a4 <> 0) LEFT JOIN t5 ON t5.a5 = t2.a2;
SET SESSION join_cache_level = 6;
EXPLAIN
SELECT t4.a4, t5.b5
FROM ((t1 LEFT JOIN (t2 JOIN t3 ON t2.a2 = t3.a3) ON t2.b2 = t1.a1)
LEFT JOIN t4 ON t4.a4 <> 0) LEFT JOIN t5 ON t5.a5 = t2.a2;
SELECT t4.a4, t5.b5
FROM ((t1 LEFT JOIN (t2 JOIN t3 ON t2.a2 = t3.a3) ON t2.b2 = t1.a1)
LEFT JOIN t4 ON t4.a4 <> 0) LEFT JOIN t5 ON t5.a5 = t2.a2;
SET SESSION optimizer_switch = 'outer_join_with_cache=off';
SET SESSION join_cache_level = DEFAULT;
DROP TABLE t1,t2,t3,t4,t5;
# this must be the last command in the file
set @@optimizer_switch=@save_optimizer_switch;

19
sql/sql_join_cache.cc
View File

@ -1776,7 +1776,13 @@ uint JOIN_CACHE::read_record_field(CACHE_FIELD *copy, bool blob_in_rec_buff)
If the value of *len is 0 then the function sets it to the total
length of the record fields including possible trailing offset
values. Otherwise *len is supposed to provide this value that
has been obtained earlier.
has been obtained earlier.
NOTE
If the value of the referenced field is null then the offset
for the value is set to 0. If the value of a field can be null
then the value of flag_fields is always positive. So the offset
for any non-null value cannot be 0 in this case.
RETURN VALUE
TRUE 'copy' points to a data descriptor of this join cache
@ -1805,14 +1811,21 @@ bool JOIN_CACHE::read_referenced_field(CACHE_FIELD *copy,
size_of_fld_ofs*
(referenced_fields+1-copy->referenced_field_no));
bool is_null= FALSE;
Field *field= copy->field;
if (offset == 0 && flag_fields)
is_null= TRUE;
if (is_null)
copy->field->set_null();
{
field->set_null();
if (!field->real_maybe_null())
field->table->null_row= 1;
}
else
{
uchar *save_pos= pos;
copy->field->set_notnull();
field->set_notnull();
if (!field->real_maybe_null())
field->table->null_row= 0;
pos= rec_ptr+offset;
read_record_field(copy, blob_data_is_in_rec_buff(rec_ptr));
pos= save_pos;