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MDEV-27744 LPAD in vcol created in ORACLE mode makes table corrupted in non-ORACLE

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The crash happened with an indexed virtual column whose
value is evaluated using a function that has a different meaning
in sql_mode='' vs sql_mode=ORACLE:

- DECODE()
- LTRIM()
- RTRIM()
- LPAD()
- RPAD()
- REPLACE()
- SUBSTR()

For example:

CREATE TABLE t1 (
  b VARCHAR(1),
  g CHAR(1) GENERATED ALWAYS AS (SUBSTR(b,0,0)) VIRTUAL,
  KEY g(g)
);

So far we had replacement XXX_ORACLE() functions for all mentioned function,
e.g. SUBSTR_ORACLE() for SUBSTR(). So it was possible to correctly re-parse
SUBSTR_ORACLE() even in sql_mode=''.

But it was not possible to re-parse the MariaDB version of SUBSTR()
after switching to sql_mode=ORACLE. It was erroneously mis-interpreted
as SUBSTR_ORACLE().

As a result, this combination worked fine:

SET sql_mode=ORACLE;
CREATE TABLE t1 ... g CHAR(1) GENERATED ALWAYS AS (SUBSTR(b,0,0)) VIRTUAL, ...;
INSERT ...
FLUSH TABLES;
SET sql_mode='';
INSERT ...

But the other way around it crashed:

SET sql_mode='';
CREATE TABLE t1 ... g CHAR(1) GENERATED ALWAYS AS (SUBSTR(b,0,0)) VIRTUAL, ...;
INSERT ...
FLUSH TABLES;
SET sql_mode=ORACLE;
INSERT ...

At CREATE time, SUBSTR was instantiated as Item_func_substr and printed
in the FRM file as substr(). At re-open time with sql_mode=ORACLE, "substr()"
was erroneously instantiated as Item_func_substr_oracle.

Fix:

The fix proposes a symmetric solution. It provides a way to re-parse reliably
all sql_mode dependent functions to their original CREATE TABLE time meaning,
no matter what the open-time sql_mode is.

We take advantage of the same idea we previously used to resolve sql_mode
dependent data types.

Now all sql_mode dependent functions are printed by SHOW using a schema
qualifier when the current sql_mode differs from the function sql_mode:

SET sql_mode='';
CREATE TABLE t1 ... SUBSTR(a,b,c) ..;
SET sql_mode=ORACLE;
SHOW CREATE TABLE t1;   ->   mariadb_schema.substr(a,b,c)

SET sql_mode=ORACLE;
CREATE TABLE t2 ... SUBSTR(a,b,c) ..;
SET sql_mode='';
SHOW CREATE TABLE t1;   ->   oracle_schema.substr(a,b,c)

Old replacement names like substr_oracle() are still understood for
backward compatibility and used in FRM files (for downgrade compatibility),
but they are not printed by SHOW any more.
This commit is contained in:
Alexander Barkov
2022-04-04 14:50:21 +04:00
parent 228b7e4db5
commit 2b6d241ee4
34 changed files with 3754 additions and 126 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
mysql-test/suite/compat/oracle/r/func_decode.result
View File

@ -28,7 +28,7 @@ EXPLAIN EXTENDED SELECT DECODE(12,10,'x10',11,'x11','def');
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1003 select decode_oracle(12,10,'x10',11,'x11','def') AS "DECODE(12,10,'x10',11,'x11','def')"
Note 1003 select decode(12,10,'x10',11,'x11','def') AS "DECODE(12,10,'x10',11,'x11','def')"
CREATE TABLE decode (decode int);
DROP TABLE decode;
#
@ -46,22 +46,22 @@ EXPLAIN EXTENDED SELECT DECODE(12,10,'x10',11,'x11');
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1003 select decode_oracle(12,10,'x10',11,'x11') AS "DECODE(12,10,'x10',11,'x11')"
Note 1003 select decode(12,10,'x10',11,'x11') AS "DECODE(12,10,'x10',11,'x11')"
EXPLAIN EXTENDED SELECT DECODE(12,10,'x10',11,'x11','def');
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1003 select decode_oracle(12,10,'x10',11,'x11','def') AS "DECODE(12,10,'x10',11,'x11','def')"
Note 1003 select decode(12,10,'x10',11,'x11','def') AS "DECODE(12,10,'x10',11,'x11','def')"
EXPLAIN EXTENDED SELECT DECODE_ORACLE(12,10,'x10',11,'x11');
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1003 select decode_oracle(12,10,'x10',11,'x11') AS "DECODE_ORACLE(12,10,'x10',11,'x11')"
Note 1003 select decode(12,10,'x10',11,'x11') AS "DECODE_ORACLE(12,10,'x10',11,'x11')"
EXPLAIN EXTENDED SELECT DECODE_ORACLE(12,10,'x10',11,'x11','def');
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1003 select decode_oracle(12,10,'x10',11,'x11','def') AS "DECODE_ORACLE(12,10,'x10',11,'x11','def')"
Note 1003 select decode(12,10,'x10',11,'x11','def') AS "DECODE_ORACLE(12,10,'x10',11,'x11','def')"
CREATE TABLE t1 (a INT);
CREATE VIEW v1 AS
SELECT
@ -72,7 +72,7 @@ DECODE_ORACLE(a,1,'x1',NULL,'xNULL','xELSE') AS d4
FROM t1;
SHOW CREATE VIEW v1;
View Create View character_set_client collation_connection
v1 CREATE VIEW "v1" AS select decode_oracle("t1"."a",1,'x1',NULL,'xNULL') AS "d1",decode_oracle("t1"."a",1,'x1',NULL,'xNULL','xELSE') AS "d2",decode_oracle("t1"."a",1,'x1',NULL,'xNULL') AS "d3",decode_oracle("t1"."a",1,'x1',NULL,'xNULL','xELSE') AS "d4" from "t1" latin1 latin1_swedish_ci
v1 CREATE VIEW "v1" AS select decode("t1"."a",1,'x1',NULL,'xNULL') AS "d1",decode("t1"."a",1,'x1',NULL,'xNULL','xELSE') AS "d2",decode("t1"."a",1,'x1',NULL,'xNULL') AS "d3",decode("t1"."a",1,'x1',NULL,'xNULL','xELSE') AS "d4" from "t1" latin1 latin1_swedish_ci
DROP VIEW v1;
DROP TABLE t1;
SELECT DECODE(TIME'10:20:31','10:20:31','then1','10:20:32','then2','def');