MDEV-20763 Table corruption or Assertion `btr_validate_index(index, 0, false)'...

MDEV-20763 Table corruption or Assertion `btr_validate_index(index, 0, false)' failed in row_upd_sec_index_entry with virtual column and EMPTY_STRING_IS_NULL SQL mode

unset empty_string_is_null mode when parsing generated columns in a table,
this mode affects pasring.

mysql-test/main/empty_string_literal.result

@@ -179,3 +179,32 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 Warnings:
 Note	1003	select NULL AS `NULL`
+#
+# MDEV-20763 Table corruption or Assertion `btr_validate_index(index, 0, false)' failed in row_upd_sec_index_entry with virtual column and EMPTY_STRING_IS_NULL SQL mode
+#
+create table t1 (a int, b binary(1) generated always as (''), key(a,b));
+insert into t1 (a) values (1);
+set sql_mode= default;
+flush tables;
+update t1 set a = 2;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL,
+  `b` binary(1) GENERATED ALWAYS AS (NULL) VIRTUAL,
+  KEY `a` (`a`,`b`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;
+create table t1 (a int, b binary(1) generated always as (''), key(a,b));
+insert into t1 (a) values (1);
+set sql_mode= 'empty_string_is_null';
+flush tables;
+update t1 set a = 2;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL,
+  `b` binary(1) GENERATED ALWAYS AS ('') VIRTUAL,
+  KEY `a` (`a`,`b`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;

mysql-test/main/empty_string_literal.test

@@ -6,3 +6,22 @@ USE test;
 set @mode='EMPTY_STRING_IS_NULL';
 
 --source include/empty_string_literal.inc
+
+--echo #
+--echo # MDEV-20763 Table corruption or Assertion `btr_validate_index(index, 0, false)' failed in row_upd_sec_index_entry with virtual column and EMPTY_STRING_IS_NULL SQL mode
+--echo #
+create table t1 (a int, b binary(1) generated always as (''), key(a,b));
+insert into t1 (a) values (1);
+set sql_mode= default;
+flush tables;
+update t1 set a = 2;
+show create table t1;
+drop table t1;
+
+create table t1 (a int, b binary(1) generated always as (''), key(a,b));
+insert into t1 (a) values (1);
+set sql_mode= 'empty_string_is_null';
+flush tables;
+update t1 set a = 2;
+show create table t1;
+drop table t1;

sql/table.cc

@@ -1051,7 +1051,7 @@ bool parse_vcol_defs(THD *thd, MEM_ROOT *mem_root, TABLE *table,
   thd->stmt_arena= table->expr_arena;
   thd->update_charset(&my_charset_utf8mb4_general_ci, table->s->table_charset);
   expr_str.append(&parse_vcol_keyword);
-  thd->variables.sql_mode &= ~MODE_NO_BACKSLASH_ESCAPES;
+  thd->variables.sql_mode &= ~(MODE_NO_BACKSLASH_ESCAPES | MODE_EMPTY_STRING_IS_NULL);
 
   while (pos < end)
   {