MDEV-26453 Assertion `0' failed in row_upd_sec_index_entry & corruption

Long UNIQUE HASH index silently creates virtual column index, which should
be impossible for base columns featuring AUTO_INCREMENT.

Fix: add a relevant check; add new vcol type for a prettier error message.

4 files changed, 38 insertions, 0 deletions

diff --git a/mysql-test/main/long_unique_bugs.result b/mysql-test/main/long_unique_bugs.result
index 5d6c0562c8a..738744867c0 100644
--- a/mysql-test/main/long_unique_bugs.result
+++ b/mysql-test/main/long_unique_bugs.result
@@ -288,3 +288,17 @@ Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_par
 t2	0	a	1	a	A	NULL	NULL	NULL	YES	HASH		
 t2	0	a	2	b	A	NULL	NULL	NULL	YES	HASH		
 DROP TABLE t1,t2;
+#
+# MDEV-26453 Assertion `0' failed in row_upd_sec_index_entry & corruption
+#
+CREATE TABLE t (c INT AUTO_INCREMENT KEY, UNIQUE USING HASH(c));
+ERROR HY000: Function or expression 'AUTO_INCREMENT' cannot be used in the USING HASH clause of `c`
+CREATE TABLE t (c INT AUTO_INCREMENT KEY);
+CREATE UNIQUE INDEX i USING HASH ON t (c);
+ERROR HY000: Function or expression 'AUTO_INCREMENT' cannot be used in the USING HASH clause of `c`
+INSERT INTO t VALUES (0);
+SELECT * FROM t;
+c
+1
+DELETE FROM t;
+DROP TABLE t;
diff --git a/mysql-test/main/long_unique_bugs.test b/mysql-test/main/long_unique_bugs.test
index 34d02b1c8f4..319940690ea 100644
--- a/mysql-test/main/long_unique_bugs.test
+++ b/mysql-test/main/long_unique_bugs.test
@@ -368,3 +368,19 @@ show index from t2;
 
 # Cleanup
 DROP TABLE t1,t2;
+
+--echo #
+--echo # MDEV-26453 Assertion `0' failed in row_upd_sec_index_entry & corruption
+--echo #
+
+--error ER_GENERATED_COLUMN_FUNCTION_IS_NOT_ALLOWED
+CREATE TABLE t (c INT AUTO_INCREMENT KEY, UNIQUE USING HASH(c));
+
+CREATE TABLE t (c INT AUTO_INCREMENT KEY);
+--error ER_GENERATED_COLUMN_FUNCTION_IS_NOT_ALLOWED
+CREATE UNIQUE INDEX i USING HASH ON t (c);
+INSERT INTO t VALUES (0);
+SELECT * FROM t;
+DELETE FROM t;
+
+DROP TABLE t;
diff --git a/sql/field.h b/sql/field.h
index a51f279e59b..c19a501f1f9 100644
--- a/sql/field.h
+++ b/sql/field.h
@@ -475,6 +475,7 @@ enum enum_vcol_info_type
 {
   VCOL_GENERATED_VIRTUAL, VCOL_GENERATED_STORED,
   VCOL_DEFAULT, VCOL_CHECK_FIELD, VCOL_CHECK_TABLE,
+  VCOL_USING_HASH,
   /* Additional types should be added here */
   /* Following is the highest value last   */
   VCOL_TYPE_NONE = 127 // Since the 0 value is already in use
@@ -492,6 +493,8 @@ static inline const char *vcol_type_name(enum_vcol_info_type type)
   case VCOL_CHECK_FIELD:
   case VCOL_CHECK_TABLE:
     return "CHECK";
+  case VCOL_USING_HASH:
+    return "USING HASH";
   case VCOL_TYPE_NONE:
     return "UNTYPED";
   }
diff --git a/sql/table.cc b/sql/table.cc
index 9a2b2819455..4df5af7a6c3 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -1065,6 +1065,8 @@ static void mysql57_calculate_null_position(TABLE_SHARE *share,
   }
 }
 
+static bool fix_and_check_vcol_expr(THD *thd, TABLE *table,
+                                    Virtual_column_info *vcol);
 
 /** Parse TABLE_SHARE::vcol_defs
 
@@ -1256,6 +1258,9 @@ bool parse_vcol_defs(THD *thd, MEM_ROOT *mem_root, TABLE *table,
       Virtual_column_info *v= new (mem_root) Virtual_column_info();
       field->vcol_info= v;
       field->vcol_info->expr= hash_item;
+      field->vcol_info->set_vcol_type(VCOL_USING_HASH);
+      if (fix_and_check_vcol_expr(thd, table, v))
+        goto end;
       key->user_defined_key_parts= key->ext_key_parts= key->usable_key_parts= 1;
       key->key_part+= parts;