From dc719597ee0b11da722e9813639e8b48018a8c10 Mon Sep 17 00:00:00 2001
From: Alexander Barkov <bar@mariadb.com>
Date: Mon, 26 Aug 2019 15:28:32 +0400
Subject: 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.
---
 sql/item.h | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

(limited to 'sql/item.h')

diff --git a/sql/item.h b/sql/item.h
index 2239544dc88..ff4cfd6c1b8 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -1216,6 +1216,32 @@ public:
   double val_real_from_decimal();
   double val_real_from_date();
 
+  /*
+    Returns true if this item can be calculated during
+    value_depends_on_sql_mode()
+  */
+  bool value_depends_on_sql_mode_const_item()
+  {
+    /*
+      Currently we use value_depends_on_sql_mode() only for virtual
+      column expressions. They should not contain any expensive items.
+      If we ever get a crash on the assert below, it means
+      check_vcol_func_processor() is badly implemented for this item.
+    */
+    DBUG_ASSERT(!is_expensive());
+    /*
+      It should return const_item() actually.
+      But for some reasons Item_field::const_item() returns true
+      at value_depends_on_sql_mode() call time.
+      This should be checked and fixed.
+    */
+    return basic_const_item();
+  }
+  virtual Sql_mode_dependency value_depends_on_sql_mode() const
+  {
+    return Sql_mode_dependency();
+  }
+
   // Get TIME, DATE or DATETIME using proper sql_mode flags for the field type
   bool get_temporal_with_sql_mode(MYSQL_TIME *ltime);
   // Check NULL value for a TIME, DATE or DATETIME expression
@@ -2694,6 +2720,10 @@ public:
   {
     return MONOTONIC_STRICT_INCREASING;
   }
+  Sql_mode_dependency value_depends_on_sql_mode() const
+  {
+    return Sql_mode_dependency(0, field->value_depends_on_sql_mode());
+  }
   longlong val_int_endpoint(bool left_endp, bool *incl_endp);
   bool get_date(MYSQL_TIME *ltime, ulonglong fuzzydate);
   bool get_date_result(MYSQL_TIME *ltime,ulonglong fuzzydate);
@@ -4102,6 +4132,7 @@ public:
   inline Item **arguments() const { return args; }
   inline uint argument_count() const { return arg_count; }
   inline void remove_arguments() { arg_count=0; }
+  Sql_mode_dependency value_depends_on_sql_mode_bit_or() const;
 };
 
 
@@ -4334,6 +4365,10 @@ public:
   bool const_item() const { return const_item_cache; }
   table_map used_tables() const { return used_tables_cache; }
   Item* build_clone(THD *thd, MEM_ROOT *mem_root);
+  Sql_mode_dependency value_depends_on_sql_mode() const
+  {
+    return Item_args::value_depends_on_sql_mode_bit_or().soft_to_hard();
+  }
 };
 
 
-- 
cgit v1.2.1