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) | Corruptionbb-10.3-bar-MDEV-27744

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.

1 files changed, 14 insertions, 1 deletions

diff --git a/sql/mysqld.h b/sql/mysqld.h
index f7d0fce910f..aa1bf855380 100644
--- a/sql/mysqld.h
+++ b/sql/mysqld.h
@@ -740,12 +740,25 @@ enum enum_query_type
                         QT_ITEM_SUBSELECT_ID_ONLY,
 
   QT_SHOW_SELECT_NUMBER= (1<<10),
+
+  //QT_ITEM_IDENT_DISABLE_DB_TABLE_NAMES= (1 <<11), -- this is taken in 10.5
+
+  /// Print sql_mode-dependent functions with the schema qualifier
+  /// even if the currently implied (by sql_mode) schema is equal to
+  /// to the function schema, e.g. mariadb_schema.concat('a').
+  QT_ITEM_FUNC_FORCE_SCHEMA_NAME= (1 << 12),
+
+  /// Print for FRM file. Focus on parse-back.
+  /// e.g. VIEW expressions and virtual column expressions
+  QT_FOR_FRM= (1 << 13),
+
   /// This is used for EXPLAIN EXTENDED extra warnings / Be more detailed
   /// Be more detailed than QT_EXPLAIN.
   /// Perhaps we should eventually include QT_ITEM_IDENT_SKIP_CURRENT_DATABASE
   /// here, as it would give better readable results
   QT_EXPLAIN_EXTENDED=  QT_TO_SYSTEM_CHARSET|
-                        QT_SHOW_SELECT_NUMBER,
+                        QT_SHOW_SELECT_NUMBER|
+                        QT_ITEM_FUNC_FORCE_SCHEMA_NAME,
 
   // If an expression is constant, print the expression, not the value
   // it evaluates to. Should be used for error messages, so that they