From f144ce2cfa086182fbd2b44408c70bd3456408f2 Mon Sep 17 00:00:00 2001
From: Sergei Golubchik <serg@mariadb.org>
Date: Tue, 5 Jan 2021 11:42:34 +0100
Subject: [PATCH] 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 | 29 +++++++++++++++++++++
 mysql-test/main/empty_string_literal.test   | 19 ++++++++++++++
 sql/table.cc                                |  2 +-
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/mysql-test/main/empty_string_literal.result b/mysql-test/main/empty_string_literal.result
index 2ca491a7dd8..bbcf27cf993 100644
--- a/mysql-test/main/empty_string_literal.result
+++ b/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;
diff --git a/mysql-test/main/empty_string_literal.test b/mysql-test/main/empty_string_literal.test
index 71e98d872bb..9174a7714a2 100644
--- a/mysql-test/main/empty_string_literal.test
+++ b/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;
diff --git a/sql/table.cc b/sql/table.cc
index 403b68551a0..22cf3357ac7 100644
--- a/sql/table.cc
+++ b/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)
   {