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, 41 insertions, 12 deletions

diff --git a/sql/item_create.h b/sql/item_create.h
index 894e9777b8d..3fadaecb090 100644
--- a/sql/item_create.h
+++ b/sql/item_create.h
@@ -145,16 +145,6 @@ protected:
 
 
 /**
-  Find the native function builder associated with a given function name.
-  @param thd The current thread
-  @param name The native function name
-  @return The native function builder associated with the name, or NULL
-*/
-extern Create_func *find_native_function_builder(THD *thd,
-                                                 const LEX_CSTRING *name);
-
-
-/**
   Find the function builder for qualified functions.
   @param thd The current thread
   @return A function builder for qualified functions
@@ -215,9 +205,48 @@ struct Native_func_registry
   Create_func *builder;
 };
 
+
+class Native_functions_hash: public HASH
+{
+public:
+  Native_functions_hash()
+  {
+    bzero(this, sizeof(*this));
+  }
+  ~Native_functions_hash()
+  {
+    /*
+      No automatic free.
+      The the upper level code should call cleanup() explicitly.
+    */
+    DBUG_ASSERT(!records);
+  }
+  bool init(size_t count);
+  bool init(const Native_func_registry array[], size_t count)
+  {
+    return init(count) || append(array);
+  }
+  bool append(const Native_func_registry array[]);
+  bool remove(const Native_func_registry array[]);
+  void cleanup();
+  /**
+    Find the native function builder associated with a given function name.
+    @param thd The current thread
+    @param name The native function name
+    @return The native function builder associated with the name, or NULL
+  */
+  Create_func *find(THD *thd, const LEX_CSTRING &name) const;
+};
+
+extern Native_functions_hash native_functions_hash;
+extern Native_functions_hash native_functions_hash_oracle_overrides;
+
+extern const Native_func_registry func_array[];
+extern const size_t func_array_length;
+
 int item_create_init();
-int item_create_append(Native_func_registry array[]);
-int item_create_remove(Native_func_registry array[]);
+int item_create_append(const Native_func_registry array[]);
+int item_create_remove(const Native_func_registry array[]);
 void item_create_cleanup();
 
 Item *create_func_dyncol_create(THD *thd, List<DYNCALL_CREATE_DEF> &list);