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, 1 insertions, 1 deletions

diff --git a/sql/sp_head.cc b/sql/sp_head.cc
index 6b116cb4550..c2d42cd830f 100644
--- a/sql/sp_head.cc
+++ b/sql/sp_head.cc
@@ -4027,7 +4027,7 @@ sp_instr_hpush_jump::execute(THD *thd, uint *nextp)
 {
   DBUG_ENTER("sp_instr_hpush_jump::execute");
 
-  int ret= thd->spcont->push_handler(m_handler, m_ip + 1);
+  int ret= thd->spcont->push_handler(this);
 
   *nextp= m_dest;