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MDEV-23799 CREATE .. SELECT wrong result on join versioned table

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For join to work correctly versioning condition must be added to table
on_expr. Without that JOIN_CACHE gets expression (1)

  trigcond(xtitle.row_end = TIMESTAMP'2038-01-19 06:14:07.999999') and
  trigcond(xtitle.elementId = x.`id` and xtitle.pkey = 'title')

instead of (2)

  trigcond(xtitle.elementId = x.`id` and xtitle.pkey = 'title')

for join_null_complements(). It is NULL-row of xtitle for
complementing the join and the above comparisons of course FALSE, but
trigcond (Item_func_trig_cond) makes them TRUE via its trig_var
property which is bound to some boolean properties of JOIN_TAB.

Expression (2) evaluated to TRUE because its trig_var is bound to
first_inner_tab->not_null_compl. The expression (1) does not evaluate
correctly because row_end comparison's trig_var is bound to
first_inner->found earlier. As a result JOIN_CACHE::check_match()
skipped the row for join_null_complements().

When we add versioning condition to table's on_expr the optimizer in
make_join_select() distributes conditions differently. tmp_cond
inherits on_expr value and in Good case it is full expression

xgender.elementId = x.`id` and xgender.pkey = 'gender' and
xgender.row_end = TIMESTAMP'2038-01-19 06:14:07.999999'

while in Bad case it is only

xgender.elementId = x.`id` and xgender.pkey = 'gender'.

Later in Good row_end condition is optimized out and we get one
trigcond in form of (2).
This commit is contained in:
Aleksey Midenkov
2020-10-20 10:49:54 +03:00
parent 7b7ea33124
commit a3c379ea61
3 changed files with 43 additions and 0 deletions
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21
mysql-test/suite/versioning/r/select.result
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@ -609,6 +609,27 @@ ERROR 22007: Incorrect date value: 'foo' for column `test`.`t2`.`b` at row 1
drop prepare stmt;
drop procedure pr;
drop table t1, t2;
#
# MDEV-23799 CREATE .. SELECT wrong result on join versioned table
#
create or replace table x (id Int) with system versioning;
create or replace table x_p (elementId Int, pkey varchar(20), pvalue varchar(20)) with system versioning;
insert into x values (1), (2), (3);
insert into x_p values (1, 'gender', 'male');
insert into x_p values (2, 'gender', 'female');
insert into x_p values (3, 'gender', 'male');
create table tmp1
select xgender.pvalue as gender, xtitle.pvalue as title
from x
left join x_p as xgender on x.id = xgender.elementId and xgender.pkey = 'gender'
left join x_p as xtitle on x.id = xtitle.elementId and xtitle.pkey = 'title';
select * from tmp1;
gender title
male NULL
female NULL
male NULL
drop table tmp1;
drop tables x, x_p;
call verify_trt_dummy(34);
No A B C D
1 1 1 1 1