MDEV-16584 SP with a cursor inside a loop wastes THD memory aggressively

Problem:

push_handler() created sp_handler_entry instances on THD::main_mem_root,
which is freed only after the SP instructions execution.
So in case of a CONTINUE HANDLER inside a loop (e.g. WHILE) this approach
leaked thread memory on every loop iteration.

Changes:
- Removing sp_handler_entry declaration, it's not really needed.
- Fixing the data type of sp_rcontext::m_handlers from
  Dynamic_array<sp_handler_entry*> to Dynamic_array<sp_instr_hpush_jump*>
- Fixing sp_rcontext::push_handler() to push the pointer to
  an sp_instr_hpush_jump instance to the handler stack.
  This instance contains everything we need.
  There is no a need to allocate anything else.

1 files changed, 50 insertions, 0 deletions

diff --git a/mysql-test/main/sp-condition-handler.test b/mysql-test/main/sp-condition-handler.test
new file mode 100644
index 00000000000..29f841607e2
--- /dev/null
+++ b/mysql-test/main/sp-condition-handler.test
@@ -0,0 +1,50 @@
+
+--echo #
+--echo # Start of 10.3 tests
+--echo #
+
+--echo #
+--echo # MDEV-16595 SP with a CONTINUE HANDLER inside a loop wastes THD memory aggressively
+--echo #
+
+DELIMITER $$;
+CREATE PROCEDURE p1()
+BEGIN
+  DECLARE mem_used_old BIGINT UNSIGNED DEFAULT
+    (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.SESSION_STATUS
+     WHERE VARIABLE_NAME='MEMORY_USED');
+  DECLARE i INT DEFAULT 1;
+  WHILE i <= 1000
+  DO
+    BEGIN
+      DECLARE msg TEXT;
+      DECLARE mem_used_cur BIGINT UNSIGNED DEFAULT
+        (SELECT VARIABLE_VALUE FROM INFORMATION_SCHEMA.SESSION_STATUS
+         WHERE VARIABLE_NAME='MEMORY_USED');
+      DECLARE CONTINUE HANDLER FOR SQLSTATE '23000' SET @x=1;
+      DECLARE CONTINUE HANDLER FOR SQLSTATE '23001' SET @x=1;
+      DECLARE CONTINUE HANDLER FOR SQLSTATE '23002' SET @x=1;
+      DECLARE CONTINUE HANDLER FOR SQLSTATE '23003' SET @x=1;
+      DECLARE CONTINUE HANDLER FOR SQLSTATE '23004' SET @x=1;
+      DECLARE CONTINUE HANDLER FOR SQLSTATE '23005' SET @x=1;
+      DECLARE CONTINUE HANDLER FOR SQLSTATE '23006' SET @x=1;
+      DECLARE CONTINUE HANDLER FOR SQLSTATE '23007' SET @x=1;
+      DECLARE CONTINUE HANDLER FOR SQLSTATE '23008' SET @x=1;
+      IF (mem_used_cur >= mem_used_old * 1.1) THEN
+        SHOW STATUS LIKE 'Memory_used';
+        SET msg=CONCAT('Memory leak detected: i=', i, ' mem_used_old=',mem_used_old,' mem_used_cur=', mem_used_cur);
+        SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT=msg;
+      END IF;
+    END;
+    SET i=i+1;
+  END WHILE;
+END;
+$$
+DELIMITER ;$$
+CALL p1;
+DROP PROCEDURE p1;
+
+
+--echo #
+--echo # End of 10.3 tests
+--echo #