MDEV-18156 Assertion `0' failed or `btr_validate_index(index, 0, false)' in row_upd_sec_index_entry or error code 126: Index is corrupted upon DELETE with PAD_CHAR_TO_FULL_LENGTH

This change takes into account a column's GENERATED ALWAYS AS
expression dependcy on sql_mode's PAD_CHAR_TO_FULL_LENGTH and
NO_UNSIGNED_SUBTRACTION flags.

Indexed virtual columns as well as persistent generated columns are
now not allowed to have such dependencies to avoid inconsistent data
or index files on sql_mode changes.
So an error is now returned in cases like this:

  CREATE OR REPLACE TABLE t1
  (
    a CHAR(5),
    v VARCHAR(5) AS (a) PERSISTENT -- CHAR->VARCHAR or CHAR->TEXT = ERROR
  );

Functions RPAD() and RTRIM() can now remove dependency on
PAD_CHAR_TO_FULL_LENGTH. So this can be used instead:

  CREATE OR REPLACE TABLE t1
  (
    a CHAR(5),
    v VARCHAR(5) AS (RTRIM(a)) PERSISTENT
  );

Note, unlike CHAR->VARCHAR and CHAR->TEXT this still works,
not RPAD(a) is needed:

  CREATE OR REPLACE TABLE t1
  (
    a CHAR(5),
    v CHAR(5) AS (a) PERSISTENT -- CHAR->CHAR is OK
  );

More sql_mode flags may affect values of generated columns.
They will be addressed separately.

See comments in sql_mode.h for implementation details.

1 files changed, 34 insertions, 0 deletions

diff --git a/sql/sql_mode.cc b/sql/sql_mode.cc
new file mode 100644
index 00000000000..9eea6ccdb52
--- /dev/null
+++ b/sql/sql_mode.cc
@@ -0,0 +1,34 @@
+/*
+   Copyright (c) 2019, MariaDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */
+
+#include "mysqld.h"
+#include "set_var.h"
+
+void Sql_mode_dependency::push_dependency_warnings(THD *thd)
+{
+  sql_mode_t all= m_hard | m_soft;
+  for (uint i= 0; all ; i++, all >>= 1)
+  {
+    if (all & 1)
+    {
+      // TODO-10.5: add a new error code
+      push_warning_printf(thd,
+                          Sql_condition::WARN_LEVEL_WARN, ER_UNKNOWN_ERROR,
+                          "Expression depends on the @@%s value %s",
+                          "sql_mode", sql_mode_string_representation(i));
+    }
+  }
+}