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

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, 94 insertions, 0 deletions

diff --git a/sql/sql_schema.cc b/sql/sql_schema.cc
index 0bf4a63c2f8..e2993f51c6d 100644
--- a/sql/sql_schema.cc
+++ b/sql/sql_schema.cc
@@ -32,6 +32,16 @@ public:
       return thd->type_handler_for_datetime();
     return src;
   }
+
+  Create_func *find_native_function_builder(THD*, const LEX_CSTRING&) const;
+
+  Item *make_item_func_substr(THD *thd,
+                              const Lex_substring_spec_st &spec) const;
+  Item *make_item_func_trim(THD *thd, const Lex_trim_st &spec) const;
+  Item *make_item_func_replace(THD *thd,
+                               Item *subj,
+                               Item *find,
+                               Item *replace) const;
 };
 
 
@@ -56,6 +66,7 @@ Schema        mariadb_schema(Lex_cstring(STRING_WITH_LEN("mariadb_schema")));
 Schema_oracle oracle_schema(Lex_cstring(STRING_WITH_LEN("oracle_schema")));
 Schema_maxdb  maxdb_schema(Lex_cstring(STRING_WITH_LEN("maxdb_schema")));
 
+const Schema &oracle_schema_ref= oracle_schema;
 
 Schema *Schema::find_by_name(const LEX_CSTRING &name)
 {
@@ -78,3 +89,86 @@ Schema *Schema::find_implied(THD *thd)
     return &maxdb_schema;
   return &mariadb_schema;
 }
+
+
+Create_func *
+Schema::find_native_function_builder(THD *thd, const LEX_CSTRING &name) const
+{
+  return native_functions_hash.find(thd, name);
+}
+
+
+Create_func *
+Schema_oracle::find_native_function_builder(THD *thd,
+                                            const LEX_CSTRING &name) const
+{
+  Create_func *create= native_functions_hash_oracle_overrides.find(thd, name);
+  if (create)
+    return create;
+  return native_functions_hash.find(thd, name);
+}
+
+
+Item *Schema::make_item_func_call_native(THD *thd,
+                                         const Lex_ident_sys &name,
+                                         List<Item> *args) const
+{
+  Create_func *builder= find_native_function_builder(thd, name);
+  if (builder)
+    return builder->create_func(thd, &name, args);
+  my_error(ER_FUNCTION_NOT_DEFINED, MYF(0), name.str);
+  return NULL;
+}
+
+
+Item *Schema::make_item_func_trim(THD *thd, const Lex_trim_st &spec) const
+{
+  return spec.make_item_func_trim_std(thd);
+}
+
+
+Item *Schema::make_item_func_substr(THD *thd,
+                                    const Lex_substring_spec_st &spec) const
+{
+  return spec.m_for ?
+    new (thd->mem_root) Item_func_substr(thd, spec.m_subject, spec.m_from,
+                                              spec.m_for) :
+    new (thd->mem_root) Item_func_substr(thd, spec.m_subject, spec.m_from);
+}
+
+
+Item *Schema_oracle::make_item_func_substr(THD *thd,
+                                    const Lex_substring_spec_st &spec) const
+{
+  return spec.m_for ?
+    new (thd->mem_root) Item_func_substr_oracle(thd, spec.m_subject,
+                                                     spec.m_from,
+                                                     spec.m_for) :
+    new (thd->mem_root) Item_func_substr_oracle(thd, spec.m_subject,
+                                                     spec.m_from);
+}
+
+
+Item *Schema_oracle::make_item_func_trim(THD *thd,
+                                         const Lex_trim_st &spec) const
+{
+  return spec.make_item_func_trim_oracle(thd);
+}
+
+
+Item *Schema::make_item_func_replace(THD *thd,
+                                     Item *subj,
+                                     Item *find,
+                                     Item *replace) const
+{
+  return new (thd->mem_root) Item_func_replace(thd, subj, find, replace);
+}
+
+
+Item *Schema_oracle::make_item_func_replace(THD *thd,
+                                            Item *subj,
+                                            Item *find,
+                                            Item *replace) const
+{
+  return new (thd->mem_root) Item_func_replace_oracle(thd, subj, find, replace);
+}