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, 43 insertions, 0 deletions

diff --git a/mysql-test/main/sp-condition-handler.result b/mysql-test/main/sp-condition-handler.result
new file mode 100644
index 00000000000..350c5d2bd3d
--- /dev/null
+++ b/mysql-test/main/sp-condition-handler.result
@@ -0,0 +1,43 @@
+#
+# Start of 10.3 tests
+#
+#
+# MDEV-16595 SP with a CONTINUE HANDLER inside a loop wastes THD memory aggressively
+#
+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;
+$$
+CALL p1;
+DROP PROCEDURE p1;
+#
+# End of 10.3 tests
+#