MDEV-31799 Unexpected ER_TRG_NO_SUCH_ROW_IN_TRG and server crash after ALTER TABLE

This bug report was caused by implementation of the task MDEV-5816
(Stored programs: validation of stored program statements).
Changing metadata of a table that has a trigger on AFTER UPDATE or AFTER DELETE
resulted in unexpected output of the error ER_TRG_NO_SUCH_ROW_IN_TR.
It was caused by the fact that characteristics of the trigger dependent on
changed table's metadata wasn't set in a new lex object created on re-parsing
of a failing trigger statement.

To fix the bug the data member lex->trg_chistics.action_time and
lex->trg_chistics.event must be set into real values of the trigger
whose statement being re-parsed.

mysql-test/main/sp_validation.result

@@ -1911,4 +1911,58 @@ CALL p1;
 # Clean up
 DROP PROCEDURE p1;
 DROP TABLE t1;
+#
+# MDEV-31799 Unexpected ER_TRG_NO_SUCH_ROW_IN_TRG and server crash after ALTER TABLE
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2),(3),(4);
+CREATE TABLE t2 (b INT);
+# Check that AFTER DELETE trigger is re-compiled on changing table's metadata
+CREATE TRIGGER tr AFTER DELETE ON t1 FOR EACH ROW INSERT INTO t2 (b) VALUES (OLD.a);
+DELETE FROM t1 LIMIT 1;
+SELECT * FROM t2;
+b
+1
+ALTER TABLE t2 FORCE;
+DELETE FROM t1 LIMIT 1;
+SELECT * FROM t2;
+b
+1
+2
+DELETE FROM t1 LIMIT 1;
+SELECT * FROM t2;
+b
+1
+2
+3
+DROP TRIGGER tr;
+# Check that AFTER UPDATE trigger is re-compiled on changing table's metadata
+CREATE TRIGGER tr AFTER UPDATE ON t1 FOR EACH ROW INSERT INTO t2 (b) VALUES (OLD.a);
+# Remove records interted by AFTER DELETE trogger
+TRUNCATE TABLE t1;
+TRUNCATE TABLE t2;
+INSERT INTO t1 VALUES (1);
+UPDATE t1 SET a = 2;
+# Above statement should insert the row (1) into the table t2
+# Expected output contains one row: (1)
+SELECT * FROM t2;
+b
+1
+ALTER TABLE t2 FORCE;
+# The following statement should insert the row (2) into the table t2
+UPDATE t1 SET a = 3;
+# Expected output contains two rows: (1), (2)
+SELECT * FROM t2;
+b
+1
+2
+# The following statement should insert the row (3) into the table t2
+UPDATE t1 SET a = 5;
+# Expected output contains three rows: (1), (2), (3)
+SELECT * FROM t2;
+b
+1
+2
+3
+DROP TABLE t1, t2;
 SET sql_mode = default;

mysql-test/main/sp_validation.test

@@ -2713,4 +2713,50 @@ CALL p1;
 DROP PROCEDURE p1;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-31799 Unexpected ER_TRG_NO_SUCH_ROW_IN_TRG and server crash after ALTER TABLE
+--echo #
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2),(3),(4);
+CREATE TABLE t2 (b INT);
+--echo # Check that AFTER DELETE trigger is re-compiled on changing table's metadata
+CREATE TRIGGER tr AFTER DELETE ON t1 FOR EACH ROW INSERT INTO t2 (b) VALUES (OLD.a);
+
+DELETE FROM t1 LIMIT 1;
+SELECT * FROM t2;
+
+ALTER TABLE t2 FORCE;
+
+DELETE FROM t1 LIMIT 1;
+SELECT * FROM t2;
+
+DELETE FROM t1 LIMIT 1;
+SELECT * FROM t2;
+
+DROP TRIGGER tr;
+--echo # Check that AFTER UPDATE trigger is re-compiled on changing table's metadata
+CREATE TRIGGER tr AFTER UPDATE ON t1 FOR EACH ROW INSERT INTO t2 (b) VALUES (OLD.a);
+--echo # Remove records interted by AFTER DELETE trogger
+TRUNCATE TABLE t1;
+TRUNCATE TABLE t2;
+INSERT INTO t1 VALUES (1);
+UPDATE t1 SET a = 2;
+--echo # Above statement should insert the row (1) into the table t2
+--echo # Expected output contains one row: (1)
+SELECT * FROM t2;
+ALTER TABLE t2 FORCE;
+
+--echo # The following statement should insert the row (2) into the table t2
+UPDATE t1 SET a = 3;
+--echo # Expected output contains two rows: (1), (2)
+SELECT * FROM t2;
+--echo # The following statement should insert the row (3) into the table t2
+UPDATE t1 SET a = 5;
+--echo # Expected output contains three rows: (1), (2), (3)
+SELECT * FROM t2;
+
+# Cleanup
+
+DROP TABLE t1, t2;
+
 SET sql_mode = default;

sql/sp_instr.cc

@@ -722,7 +722,21 @@ LEX* sp_lex_instr::parse_expr(THD *thd, sp_head *sp, LEX *sp_instr_lex)
     sp_instr_cursor_copy_struct) and in some cases for sp_instr_set.
   */
   if (sp_instr_lex == nullptr)
+  {
     thd->lex= new (thd->mem_root) st_lex_local;
+    lex_start(thd);
+    if (sp->m_handler->type() == SP_TYPE_TRIGGER)
+    {
+      /*
+        In case the trigger's statement being re-parsed, the correct trigger's
+        context (trigger event type and action time) should be copied from
+        trigger's sp_head to the new lex object.
+      */
+      thd->lex->trg_chistics.action_time=
+        thd->spcont->m_sp->m_trg->action_time;
+      thd->lex->trg_chistics.event= thd->spcont->m_sp->m_trg->event;
+    }
+  }
   else
   {
     sp_lex_cursor* cursor_lex= sp_instr_lex->get_lex_for_cursor();
@@ -742,8 +756,6 @@ LEX* sp_lex_instr::parse_expr(THD *thd, sp_head *sp, LEX *sp_instr_lex)
     DBUG_ASSERT(thd->lex == sp_instr_lex);
   }
 
-  lex_start(thd);
-
   thd->lex->sphead= sp;
   thd->lex->spcont= m_ctx;