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Message #04648
Re: Igor please review: [Commits] Rev 3464: BUG#951937: Wrong result (missing rows) with semijoin+materialization, IN subquery, InnoDB, TEMPTABLE view in file:///home/psergey/dev2/5.3-look60/]
On 03/23/2012 02:41 PM, Sergei Petrunia wrote:
> Hello Igor,
>
> Could you please review the below:
Hi Sergey,
Here's my feedback:
>
> ----- Forwarded message from Sergey Petrunya <psergey@xxxxxxxxxxxx> -----
>
> From: Sergey Petrunya <psergey@xxxxxxxxxxxx>
> To: commits@xxxxxxxxxxx
> X-Mailer: mail (GNU Mailutils 1.2)
> Date: Sat, 24 Mar 2012 01:40:02 +0400 (GST)
> Subject: [Commits] Rev 3464: BUG#951937: Wrong result (missing rows) with
> semijoin+materialization, IN subquery, InnoDB,
> TEMPTABLE view in file:///home/psergey/dev2/5.3-look60/
>
> At file:///home/psergey/dev2/5.3-look60/
>
> ------------------------------------------------------------
> revno: 3464
> revision-id: psergey@xxxxxxxxxxxx-20120323213956-ohxb9jitekne7yya
> parent: psergey@xxxxxxxxxxxx-20120321071820-t2azo8xxlm73mezd
> committer: Sergey Petrunya <psergey@xxxxxxxxxxxx>
> branch nick: 5.3-look60
> timestamp: Sat 2012-03-24 01:39:56 +0400
> message:
> BUG#951937: Wrong result (missing rows) with semijoin+materialization, IN subquery, InnoDB, TEMPTABLE view
> - Fix equality propagation to work with SJM nests and OR clauses (full descirption of problem and
> solution in the comment in the patch)
> === modified file 'mysql-test/r/subselect_sj2.result'
> --- a/mysql-test/r/subselect_sj2.result 2012-02-25 00:50:22 +0000
> +++ b/mysql-test/r/subselect_sj2.result 2012-03-23 21:39:56 +0000
> @@ -903,5 +903,48 @@
> 3 1 1
> 4 1 1
> DROP TABLE t1,t2;
> +#
> +# BUG#951937: Wrong result (missing rows) with semijoin+materialization, IN subquery, InnoDB, TEMPTABLE view
> +#
> +CREATE TABLE t1 (
> +a VARCHAR(1),
> +b VARCHAR(1) NOT NULL,
> +KEY(a)
> +) ENGINE=InnoDB;
> +INSERT INTO t1 VALUES
> +('j','j'),('v','v'),('c','c'),('m','m'),('d','d'),
> +('y','y'),('t','t'),('d','d'),('s','s'),('r','r'),
> +('m','m'),('b','b'),('x','x'),('g','g'),('p','p'),
> +('q','q'),('w','w'),('d','d'),('e','e');
> +CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
> +SELECT * FROM v1
> +WHERE ( a, a ) IN (
> +SELECT alias2.b, alias2.a
> +FROM t1 AS alias1, t1 AS alias2
> +WHERE alias2.b = alias1.a
> +AND ( alias1.b >= alias1.a OR alias2.b = 'z' )
> +);
> +a b
> +j j
> +v v
> +c c
> +m m
> +m m
> +d d
> +d d
> +d d
> +y y
> +t t
> +s s
> +r r
> +b b
> +x x
> +g g
> +p p
> +q q
> +w w
> +e e
> +DROP VIEW v1;
> +DROP TABLE t1;
> # This must be the last in the file:
> set optimizer_switch=@subselect_sj2_tmp;
>
> === modified file 'mysql-test/r/subselect_sj2_jcl6.result'
> --- a/mysql-test/r/subselect_sj2_jcl6.result 2012-02-25 00:50:22 +0000
> +++ b/mysql-test/r/subselect_sj2_jcl6.result 2012-03-23 21:39:56 +0000
> @@ -917,6 +917,49 @@
> 3 1 1
> 4 1 1
> DROP TABLE t1,t2;
> +#
> +# BUG#951937: Wrong result (missing rows) with semijoin+materialization, IN subquery, InnoDB, TEMPTABLE view
> +#
> +CREATE TABLE t1 (
> +a VARCHAR(1),
> +b VARCHAR(1) NOT NULL,
> +KEY(a)
> +) ENGINE=InnoDB;
> +INSERT INTO t1 VALUES
> +('j','j'),('v','v'),('c','c'),('m','m'),('d','d'),
> +('y','y'),('t','t'),('d','d'),('s','s'),('r','r'),
> +('m','m'),('b','b'),('x','x'),('g','g'),('p','p'),
> +('q','q'),('w','w'),('d','d'),('e','e');
> +CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
> +SELECT * FROM v1
> +WHERE ( a, a ) IN (
> +SELECT alias2.b, alias2.a
> +FROM t1 AS alias1, t1 AS alias2
> +WHERE alias2.b = alias1.a
> +AND ( alias1.b >= alias1.a OR alias2.b = 'z' )
> +);
> +a b
> +j j
> +v v
> +c c
> +m m
> +m m
> +d d
> +d d
> +d d
> +y y
> +t t
> +s s
> +r r
> +b b
> +x x
> +g g
> +p p
> +q q
> +w w
> +e e
> +DROP VIEW v1;
> +DROP TABLE t1;
> # This must be the last in the file:
> set optimizer_switch=@subselect_sj2_tmp;
> #
>
> === modified file 'mysql-test/r/subselect_sj2_mat.result'
> --- a/mysql-test/r/subselect_sj2_mat.result 2012-02-25 00:50:22 +0000
> +++ b/mysql-test/r/subselect_sj2_mat.result 2012-03-23 21:39:56 +0000
> @@ -905,6 +905,49 @@
> 3 1 1
> 4 1 1
> DROP TABLE t1,t2;
> +#
> +# BUG#951937: Wrong result (missing rows) with semijoin+materialization, IN subquery, InnoDB, TEMPTABLE view
> +#
> +CREATE TABLE t1 (
> +a VARCHAR(1),
> +b VARCHAR(1) NOT NULL,
> +KEY(a)
> +) ENGINE=InnoDB;
> +INSERT INTO t1 VALUES
> +('j','j'),('v','v'),('c','c'),('m','m'),('d','d'),
> +('y','y'),('t','t'),('d','d'),('s','s'),('r','r'),
> +('m','m'),('b','b'),('x','x'),('g','g'),('p','p'),
> +('q','q'),('w','w'),('d','d'),('e','e');
> +CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
> +SELECT * FROM v1
> +WHERE ( a, a ) IN (
> +SELECT alias2.b, alias2.a
> +FROM t1 AS alias1, t1 AS alias2
> +WHERE alias2.b = alias1.a
> +AND ( alias1.b >= alias1.a OR alias2.b = 'z' )
> +);
> +a b
> +j j
> +v v
> +c c
> +m m
> +m m
> +d d
> +d d
> +d d
> +y y
> +t t
> +s s
> +r r
> +b b
> +x x
> +g g
> +p p
> +q q
> +w w
> +e e
> +DROP VIEW v1;
> +DROP TABLE t1;
> # This must be the last in the file:
> set optimizer_switch=@subselect_sj2_tmp;
> set optimizer_switch=default;
>
> === modified file 'mysql-test/t/subselect_sj2.test'
> --- a/mysql-test/t/subselect_sj2.test 2012-01-19 19:44:43 +0000
> +++ b/mysql-test/t/subselect_sj2.test 2012-03-23 21:39:56 +0000
> @@ -1090,5 +1090,32 @@
>
> DROP TABLE t1,t2;
>
> +--echo #
> +--echo # BUG#951937: Wrong result (missing rows) with semijoin+materialization, IN subquery, InnoDB, TEMPTABLE view
> +--echo #
> +CREATE TABLE t1 (
> + a VARCHAR(1),
> + b VARCHAR(1) NOT NULL,
> + KEY(a)
> +) ENGINE=InnoDB;
> +INSERT INTO t1 VALUES
> +('j','j'),('v','v'),('c','c'),('m','m'),('d','d'),
> +('y','y'),('t','t'),('d','d'),('s','s'),('r','r'),
> +('m','m'),('b','b'),('x','x'),('g','g'),('p','p'),
> +('q','q'),('w','w'),('d','d'),('e','e');
> +
> +CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
> +
> +# This query returns 6 rows instead of 19
> +
> +SELECT * FROM v1
> +WHERE ( a, a ) IN (
> + SELECT alias2.b, alias2.a
> + FROM t1 AS alias1, t1 AS alias2
> + WHERE alias2.b = alias1.a
> + AND ( alias1.b >= alias1.a OR alias2.b = 'z' )
> +);
> +DROP VIEW v1;
> +DROP TABLE t1;
> --echo # This must be the last in the file:
> set optimizer_switch=@subselect_sj2_tmp;
I tried a test case without any view:
MariaDB [test]> CREATE TABLE t2 (a VARCHAR(1), b VARCHAR(1) NOT NULL,
KEY(a)) ENGINE=InnoDB;
Query OK, 0 rows affected (0.02 sec)
MariaDB [test]> INSERT INTO t2 SELECT * FROM t1;
Query OK, 19 rows affected (0.00 sec)
Records: 19 Duplicates: 0 Warnings: 0
MariaDB [test]> INSERT INTO t2 SELECT * FROM t1;
Query OK, 19 rows affected (0.00 sec)
Records: 19 Duplicates: 0 Warnings: 0
MariaDB [test]> EXPLAIN EXTENDED SELECT * FROM t2 WHERE ( a, a ) IN (
SELECT alias2.b, alias2.a FROM t1 AS alias1, t1 AS alias2 WHERE alias2.b
= alias1.a AND ( alias1.b >= alias1.a OR alias2.b = 'z' ) );
+----+--------------+-------------+------+---------------+------+---------+---------------+------+----------+------------------------------------+
| id | select_type | table | type | possible_keys | key |
key_len | ref | rows | filtered | Extra
|
+----+--------------+-------------+------+---------------+------+---------+---------------+------+----------+------------------------------------+
| 1 | PRIMARY | <subquery2> | ALL | distinct_key | NULL | NULL
| NULL | 19 | 100.00 | |
| 1 | PRIMARY | t2 | ref | a | a | 4
| test.alias1.a | 1 | 100.00 | Using index condition; Using where |
| 2 | MATERIALIZED | alias1 | ALL | a | NULL | NULL
| NULL | 19 | 100.00 | Using where |
| 2 | MATERIALIZED | alias2 | ref | a | a | 4
| test.alias1.a | 1 | 100.00 | Using where |
+----+--------------+-------------+------+---------------+------+---------+---------------+------+----------+------------------------------------+
4 rows in set, 1 warning (0.00 sec)
MariaDB [test]> SHOW WARNINGS;
+-------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Level | Code | Message
|
+-------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Note | 1003 | select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`
from `test`.`t2` semi join (`test`.`t1` `alias1` join `test`.`t1`
`alias2`) where ((`test`.`alias2`.`a` = `test`.`alias1`.`a`) and
(`test`.`alias2`.`b` = `test`.`alias1`.`a`) and (`test`.`t2`.`a` =
`test`.`alias1`.`a`) and ((`test`.`alias1`.`b` >= `test`.`alias1`.`a`)
or ((`test`.`alias1`.`a` = 'z') and (`test`.`t2`.`a` = 'z')))) |
+-------+------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
MariaDB [test]> SELECT * FROM t2 WHERE ( a, a ) IN ( SELECT alias2.b,
alias2.a FROM t1 AS alias1, t1 AS alias2 WHERE alias2.b = alias1.a AND (
alias1.b >= alias1.a OR alias2.b = 'z' ) );
+------+---+
| a | b |
+------+---+
| c | c |
| c | c |
| d | d |
| d | d |
| d | d |
| d | d |
| d | d |
| d | d |
| b | b |
| b | b |
| e | e |
| e | e |
+------+---+
12 rows in set (0.01 sec)
As you can see here 5.3 also have similar problems.
I would suggest this test case as the main one for this bug.
I would preserve the old one as well.
>
> === modified file 'sql/item_cmpfunc.cc'
> --- a/sql/item_cmpfunc.cc 2012-02-28 14:41:55 +0000
> +++ b/sql/item_cmpfunc.cc 2012-03-23 21:39:56 +0000
> @@ -5388,7 +5388,7 @@
> */
>
> Item_equal::Item_equal(Item *f1, Item *f2, bool with_const_item)
> - : Item_bool_func(), eval_item(0), cond_false(0)
> + : Item_bool_func(), eval_item(0), cond_false(0), context_field(NULL)
> {
> const_item_cache= 0;
> with_const= with_const_item;
> @@ -5411,7 +5411,7 @@
> */
>
> Item_equal::Item_equal(Item_equal *item_equal)
> - : Item_bool_func(), eval_item(0), cond_false(0)
> + : Item_bool_func(), eval_item(0), cond_false(0), context_field(NULL)
> {
> const_item_cache= 0;
> List_iterator_fast<Item> li(item_equal->equal_items);
>
> === modified file 'sql/item_cmpfunc.h'
> --- a/sql/item_cmpfunc.h 2012-01-19 22:11:53 +0000
> +++ b/sql/item_cmpfunc.h 2012-03-23 21:39:56 +0000
> @@ -1700,9 +1700,16 @@
> as datetimes. The comparator is used only if compare_as_dates=TRUE
> */
> Arg_comparator cmp;
> +
> + /*
> + For Item_equal objects inside an OR clause: one of the fields that were
> + used in the original comparison.
^ an original equality (?)
> + */
> + Item_field *context_field;
> public:
> inline Item_equal()
> - : Item_bool_func(), with_const(FALSE), eval_item(0), cond_false(0)
> + : Item_bool_func(), with_const(FALSE), eval_item(0), cond_false(0),
> + context_field(NULL)
> { const_item_cache=0 ;}
> Item_equal(Item *f1, Item *f2, bool with_const_item);
> Item_equal(Item_equal *item_equal);
> @@ -1729,6 +1736,8 @@
> Item *transform(Item_transformer transformer, uchar *arg);
> virtual void print(String *str, enum_query_type query_type);
> CHARSET_INFO *compare_collation();
> +
> + void set_context_field(Item_field *ctx_field) { context_field= ctx_field; }
> friend class Item_equal_fields_iterator;
> friend Item *eliminate_item_equal(COND *cond, COND_EQUAL *upper_levels,
> Item_equal *item_equal);
>
> === modified file 'sql/opt_subselect.cc'
> --- a/sql/opt_subselect.cc 2012-03-18 19:58:20 +0000
> +++ b/sql/opt_subselect.cc 2012-03-23 21:39:56 +0000
> @@ -171,6 +171,246 @@
>
> */
>
> +/*
> +EqualityPropagationAndSjmNests
> +******************************
> +
> +The process of equality propagation has two parts
^Equalities are used for:
> +P1. Equality propagation
> +P2. Equality substitution [for a certain join order]
> +
> +The propagation part is not affected by SJM nests. In fact, it is done before
^The equality propagation is ...
> +we determine the execution plan, i.e. before we even know we will use
> +SJM-nests for execution.
> +
> +The substitution part is affected.
The equality substitution is ...
> +
> +Substitution without SJMs
> +=========================
> +When one doesn't have SJM nests, tables have a strict join order:
> +
> + --------------------------------->
> + t1 -- t2 -- t3 -- t4 --- t5
> +
> +
> + ? ^
> + \
> + --(part-of-WHERE)
> +
> +
> +parts WHERE/ON and ref. expressions are attached at some point along the axis.
> +Expression is allowed to refer to a table column if the table is to the left of
> +the attachment point. For any given expression, we have a goal:
> +
> + "Move leftmost allowed attachment point as much as possible to the left"
> +
> +Substitution with SJMs - task setting
> +=====================================
> +
> +When SJM nests are present, there is no global strict table ordering anymore:
> +
> +
> + --------------------------------->
> +
> + ot1 -- ot2 --- sjm -- ot4 --- ot5
> + |
> + | Main execution
> + - - - - - - - - - - - - - - - - - - - - - - - -
> + | Materialization
> + it1 -- it2 --/
> +
> +
> +Besides that, we must take into account that
> + - values for outer table columns, otN.col, are inaccessible at
> + materialization step (SJM-RULE)
> + - values for inner table columns, itN.col, are inaccessible at Main execution
> + step, except for SJ-Materialization-Scan and columns that are in the
> + subquery's select list. (SJM-RULE)
> +
> +Substitution with SJMs - solution
> +=================================
> +
> +First, we introduce global strict table ordering like this:
> +
> + ot1 - ot2 --\ /--- ot3 -- ot5
> + \--- it1 --- it2 --/
> +
> +Now, let's see how to meet (SJM-RULE).
> +
> +SJ-Materialization is only applicable for uncorrelated subqueries. From this, it
> +follows that any multiple equality will either
> +1. include only columns of outer tables, or
> +2. include only columns of inner tables, or
> +3. include columns of inner and outer tables, joined together through one
> + of IN-equalities.
> +
> +Cases #1 and #2 can be handled in the same way as with regular inner joins.
> +
> +Case #3 requires special handling, so that we don't construct violations of
> +(SJM-RULE). Let's consider possible ways to build violations.
> +
> +Equality propagation starts with the clause in this form
> +
> + top_query_where AND subquery_where AND in_equalities
> +
> +First, it builds multi-equalities. It can also build a mixed multi-equality
> +
> + multiple-equal(ot1.col, ot2.col, ... it1.col, itN.col)
> +
> +Multi-equalities are pushed down the OR-clauses in top_query_where and in
> +subquery_where, so it's possible that clauses like this one are built:
> +
> + subquery_cond OR (multiple-equal(it1.col, ot1.col,...) AND ...)
> + ^^^^^^^^^^^^^ \
> + | this must be evaluated
> + \- can only be invaluated on the main phase
^evaluated ^at
> + on materialization phase
^at the
> +
> +Finally, equality substitution is started. It does two operations:
> +
> +
> +1. Field reference substitution
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +(In the code, this is Item_field::replace_equal_field)
> +
> +This is a process of replacing each reference to "tblX.col"
> +with the first element of the multi-equality. (REF-SUBST-ORIG)
> +
> +This behaviour can cause problems with Semi-join nests. Suppose, we have a
> +condition:
> +
> + func(it1.col, it2.col)
> +
> +and a multi-equality(ot1.col, it1.col). Then, reference to "it1.col" will be
> +replaced with "ot1.col", constructing a condition
> +
> + func(ot1.col, it2.col)
> +
> +which will be a vioation of (SJM-RULE).
^violation
> +
> +In order to avoid this, (REF-SUBST-ORIG) is amended as follows:
> +
> +- references to tables "itX.col" that are inner wrt some SJM nest, are
> + replaced with references to the first inner table from the same SJM nest.
> +
> +- references to top-level tables "otX.col" are replaced with references to
> + the first element of the multi-equality, no matter if that first element is
> + a column of a top-level table or of table from some SJM nest.
> + (REF-SUBST-SJM)
> +
> + The case where the first element is a table from an SJM nest $SJM is ok,
> + because it can be proven that $SJM uses SJ-Materialization-Scan, and
> + "unpacks" correct column values to the first element during the main
> + execution phase.
> +
> +2. Item_equal elimination
> +~~~~~~~~~~~~~~~~~~~~~~~~~
> +(In the code: eliminate_item_equal) This is a process of taking
> +
> + multiple-equal(a,b,c,d,e)
> +
> +and replacing it with an equivalent expression which is an AND of pair-wise
> +equalities:
> +
> + a=b AND a=c AND ...
> +
> +The equalities are picked such that for any given join prefix (t1,t2...) the
> +subset of equalities that can be evaluated gives the most restrictive
> +filtering.
> +
> +Without SJM nests, it is sufficient to compare every multi-equality member
> +with the first one:
> +
> + elem1=elem2 AND elem1=elem3 AND elem1=elem4 ...
> +
> +When SJM nests are present, we should take care not to construct equalities
> +that violate the (SJM-RULE). This is achieved by generating separate sets of
> +equalites for top-level tables and for inner tables. That is, for the join
> +order
> +
> + ot1 - ot2 --\ /--- ot3 -- ot5
> + \--- it1 --- it2 --/
> +
> +we will generate
> + ot1.col=ot2.col
> + ot1.col=ot3.col
> + ot1.col=ot5.col
> + it2.col=it1.col
> +
> +
> +2.1 The problem with Item_equals and ORs
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +As has been mentioned above, multiple equalities are pushed down into OR
> +clauses, possibly building clauses like this:
> +
> + func(it.col2) OR multiple-equal(it1.col1, it1.col2, ot1.col) (1)
> +
> +where the first part of the clause has references to inner tables, while the
> +second has references to the top-level tables, which is a violation of
> +(SJM-RULE).
> +
> +AND-clauses of this kind do not create problems, because make_cond_for_table()
> +will take them apart. OR-clauses will not be split. It is possible to
> +split-out the part that's dependent on the inner table:
> +
> + func(it.col2) OR it1.col1=it1.col2
> +
> +but this is a less-restrictive condition than condition (1). Current execution
> +scheme will still try to generate the "remainder" condition:
> +
> + func(it.col2) OR it1.col1=ot1.col
> +
> +which is a violation of (SJM-RULE).
> +
> +QQ: "ot1.col=it1.col" is checked at the upper level. Why was it not removed
> +here?
> +AA: because has a proper subset of conditions that are found on this level.
> + consider a join order of ot, sjm(it)
> + and a condition
> + ot.col=it.col AND ( ot.col=it.col='foo' OR it.col2='bar')
> +
> + we will produce:
> + table ot: nothing
> + table it: ot.col=it.col AND (ot.col='foo' OR it.col2='bar')
> + ^^^^ ^^^^^^^^^^^^^^^^
> + | \ the problem is that
> + | this part condition didnt
> + | receive a substitution
> + |
> + +--- it was correct to subst, 'ot' is
> + the left-most.
> +
> +
> +Is there any merit in pushing inner=outer down into ORs?
^sense?
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +Yes, there is. Consider the query:
> +
> + select * from ot
> + where ot.col in (select it.col from it where (it.col='foo' OR it.col='bar'))
> +
> +here, it may be useful to infer that
> +
> + (ot.col='foo' OR ot.col='bar') (CASE-FOR-SUBST)
> +
> +and attach that condition to the table 'ot'.
> +
> +Solution #1
> +~~~~~~~~~~~
> +Let make_cond_for_table() chop off the bad parts of produced OR clause. If it
> +has produced an OR clause:
> +- check if all of its branches are evaluable for the context join_tab
> +- If some aren't, destroy the OR clause
> +
> +Solution #2
> +~~~~~~~~~~~
> +Before the equality propagation phase, none of the OR clauses violate the
> +(SJM-RULE). This way, if we remember which tables the original equality
> +referred to, we can only generate equalities that refer to outer or inner
> +tables. Note that this will disallow handling of cases like (CASE-FOR-SUBST).
> +*/
You have to say somewhere that Solution #2 is currently chosen.
> +
>
> static
> bool subquery_types_allow_materialization(Item_in_subselect *in_subs);
>
> === modified file 'sql/sql_select.cc'
> --- a/sql/sql_select.cc 2012-03-13 20:49:18 +0000
> +++ b/sql/sql_select.cc 2012-03-23 21:39:56 +0000
> @@ -10666,6 +10666,9 @@
> acceptable, as this happens rarely. The implementation without
> copying would be much more complicated.
>
> + For description of how equality propagation works with SJM nests, grep
> + for EqualityPropagationAndSjmNests.
> +
> @param left_item left term of the quality to be checked
> @param right_item right term of the equality to be checked
> @param item equality item if the equality originates from a condition
> @@ -10739,12 +10742,14 @@
> {
> /* left_item_equal of an upper level contains left_item */
> left_item_equal= new Item_equal(left_item_equal);
> + left_item_equal->set_context_field(((Item_field*) left_item));
> cond_equal->current_level.push_back(left_item_equal);
> }
> if (right_copyfl)
> {
> /* right_item_equal of an upper level contains right_item */
> right_item_equal= new Item_equal(right_item_equal);
> + right_item_equal->set_context_field(((Item_field*) right_item));
> cond_equal->current_level.push_back(right_item_equal);
> }
>
> @@ -10830,6 +10835,7 @@
> {
> item_equal= new Item_equal(item_equal);
> cond_equal->current_level.push_back(item_equal);
> + item_equal->set_context_field(field_item);
> }
> if (item_equal)
> {
> @@ -11480,6 +11486,8 @@
> Item_equal::get_first() also takes similar measures for dealing with
> equality substitution in presense of SJM nests.
>
> + Grep for EqualityPropagationAndSjmNests for a more verbose description.
> +
> @return
> - The condition with generated simple equalities or
> a pointer to the simple generated equality, if success.
> @@ -11543,9 +11551,13 @@
> on upper AND-levels.
> */
> if (upper)
> - {
> + {
> + TABLE_LIST *native_sjm= embedding_sjm(item_equal->context_field);
> if (item_const && upper->get_const())
> + {
> + /* Upper item also has "field_item=const". Don't produce equality here */
> item= 0;
> + }
> else
> {
> Item_equal_fields_iterator li(*item_equal);
> @@ -11556,6 +11568,8 @@
> break;
> }
> }
> + if (embedding_sjm(field_item) != native_sjm)
> + item= NULL; /* Don't produce equality */
> }
>
> bool produce_equality= test(item == field_item);
>
> _______________________________________________
> commits mailing list
> commits@xxxxxxxxxxx
> https://lists.askmonty.org/cgi-bin/mailman/listinfo/commits
>
> ----- End forwarded message -----
If you agree with what I said above and ready to correct the patch
appropriately you can push it.
>
References
