Part2: 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 patch allows the server to open old tables that have
"bad" generated columns (i.e. indexed virtual generated columns,
persistent generated columns) that depend on sql_mode,
for general things like SELECT, INSERT, DROP, etc.
Warning are issued in such cases.

Only these commands are now disallowed and return an error:
- CREATE TABLE introducing a "bad" generated column
- ALTER TABLE introducing a "bad" generated column
- CREATE INDEX introdicing a "bad" generated column
  (i.e. adding an index on a virtual generated column
   that depends on sql_mode).

Note, these commands are allowed:
- ALTER TABLE removing a "bad" generate column
- ALTER TABLE removing an index from a "bad" virtual generated column
- DROP INDEX removing an index from a "bad" virtual generated column
but only if the table does not have any "bad" columns as a result.

1 files changed, 15 insertions, 1 deletions

diff --git a/sql/table.h b/sql/table.h
index 7786679982f..8f6a9e7aa86 100644
--- a/sql/table.h
+++ b/sql/table.h
@@ -325,6 +325,20 @@ enum tmp_table_type
 };
 enum release_type { RELEASE_NORMAL, RELEASE_WAIT_FOR_DROP };
 
+
+enum vcol_init_mode
+{
+  VCOL_INIT_DEPENDENCY_FAILURE_IS_WARNING= 1,
+  VCOL_INIT_DEPENDENCY_FAILURE_IS_ERROR= 2
+  /*
+    There may be new flags here.
+    e.g. to automatically remove sql_mode dependency:
+      GENERATED ALWAYS AS (char_col) ->
+      GENERATED ALWAYS AS (RTRIM(char_col))
+  */
+};
+
+
 enum enum_vcol_update_mode
 {
   VCOL_UPDATE_FOR_READ= 0,
@@ -2736,7 +2750,7 @@ bool fix_session_vcol_expr(THD *thd, Virtual_column_info *vcol);
 bool fix_session_vcol_expr_for_read(THD *thd, Field *field,
                                     Virtual_column_info *vcol);
 bool parse_vcol_defs(THD *thd, MEM_ROOT *mem_root, TABLE *table,
-                     bool *error_reported);
+                     bool *error_reported, vcol_init_mode expr);
 TABLE_SHARE *alloc_table_share(const char *db, const char *table_name,
                                const char *key, uint key_length);
 void init_tmp_table_share(THD *thd, TABLE_SHARE *share, const char *key,