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, 1 insertions, 0 deletions

diff --git a/libmysqld/CMakeLists.txt b/libmysqld/CMakeLists.txt
index 2236d306318..6ed51eff2f4 100644
--- a/libmysqld/CMakeLists.txt
+++ b/libmysqld/CMakeLists.txt
@@ -107,6 +107,7 @@ SET(SQL_EMBEDDED_SOURCES emb_qcache.cc libmysqld.c lib_sql.cc
            ../sql/sql_analyze_stmt.cc ../sql/sql_analyze_stmt.h
            ../sql/compat56.cc
            ../sql/sql_type.cc ../sql/sql_type.h
+           ../sql/sql_mode.cc
            ../sql/table_cache.cc ../sql/mf_iocache_encr.cc
            ../sql/item_inetfunc.cc
            ../sql/wsrep_dummy.cc ../sql/encryption.cc