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MDEV-24910 Crash with SELECT that uses table value constructor as a subselect

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This bug caused crashes of the server when processing queries with table
value constructors (TVC) that contained subqueries and were used itself as
subselects. For such TVCs the following transformation is applied at the
prepare stage:
  VALUES (v1), ... (vn) => SELECT * FROM (VALUES (v1), ... (vn)) tvc_x.
This transformation allows to reduce the problem of evaluation of TVCs used
as subselects to the problem of evaluation of regular subselects.
The transformation is implemented in the wrap_tvc(). The code the function
to mimic the behaviour of the parser when processing the result of the
transformation. However this imitation was not free of some flaws. First
the function called the method exclude() that completely destroyed the
select tree structures below the transformed TVC. Second the function
used the procedure mysql_new_select to create st_select_lex nodes for
both wrapping select of the transformation and TVC. This also led to
constructing of invalid select tree structures.
The patch actually re-engineers the code of wrap_tvc().

Approved by Oleksandr Byelkin <sanja@mariadb.com>
This commit is contained in:
Igor Babaev
2021-02-24 13:51:47 -08:00
parent 13f0e1e139
commit bf6484e7bb
6 changed files with 233 additions and 33 deletions
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4
mysql-test/suite/compat/oracle/r/table_value_constr.result
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@ -746,7 +746,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
3 MATERIALIZED <derived2> ALL NULL NULL NULL NULL 2 100.00
2 DERIVED NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1003 select "test"."t1"."a" AS "a","test"."t1"."b" AS "b" from "test"."t1" semi join ((values (1)) "tvc_0") where 1
Note 1003 /* select#1 */ select "test"."t1"."a" AS "a","test"."t1"."b" AS "b" from "test"."t1" semi join ((values (1)) "tvc_0") where 1
explain extended select * from t1
where a in (select * from (values (1)) as tvc_0);
id select_type table type possible_keys key key_len ref rows filtered Extra
@ -981,7 +981,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
3 MATERIALIZED <derived2> ALL NULL NULL NULL NULL 2 100.00
2 DERIVED NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1003 select "test"."t1"."a" AS "a","test"."t1"."b" AS "b" from "test"."t1" semi join ((values (1),(2)) "tvc_0") where 1
Note 1003 /* select#1 */ select "test"."t1"."a" AS "a","test"."t1"."b" AS "b" from "test"."t1" semi join ((values (1),(2)) "tvc_0") where 1
explain extended select * from t1
where a = any (select * from (values (1),(2)) as tvc_0);
id select_type table type possible_keys key key_len ref rows filtered Extra