From d67c3f88883b616a9adf3abba43938c3a07a5eee Mon Sep 17 00:00:00 2001
From: Alexander Barkov <bar@mariadb.com>
Date: Mon, 4 Apr 2022 14:50:21 +0400
Subject: MDEV-27744 InnoDB: Failing assertion: !cursor->index->is_committed()
 in row0ins.cc (from row_ins_sec_index_entry_by_modify) | Assertion `0' failed
 in row_upd_sec_index_entry (debug) | Corruption

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.
---
 sql/sql_show.cc | 3 ---
 1 file changed, 3 deletions(-)

(limited to 'sql/sql_show.cc')

diff --git a/sql/sql_show.cc b/sql/sql_show.cc
index 2a3dbceb4cb..c8a78649696 100644
--- a/sql/sql_show.cc
+++ b/sql/sql_show.cc
@@ -74,9 +74,6 @@ extern size_t symbols_length;
 extern SYMBOL sql_functions[];
 extern size_t sql_functions_length;
 
-extern Native_func_registry func_array[];
-extern size_t func_array_length;
-
 enum enum_i_s_events_fields
 {
   ISE_EVENT_CATALOG= 0,
-- 
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