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

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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.
This commit is contained in:
Alexander Barkov 2018-06-28 16:55:42 +04:00
commit 724a5105cb
6 changed files with 107 additions and 48 deletions
Download patch file Download diff file Expand all files Collapse all files

24
sql/sp_rcontext.cc
View file

@ -448,19 +448,9 @@ void sp_rcontext::pop_cursors(THD *thd, size_t count)
}
bool sp_rcontext::push_handler(sp_handler *handler, uint first_ip)
bool sp_rcontext::push_handler(sp_instr_hpush_jump *entry)
{
/*
We should create handler entries in the callers arena, as
they could be (and usually are) used in several instructions.
*/
sp_handler_entry *he=
new (callers_arena->mem_root) sp_handler_entry(handler, first_ip);
if (he == NULL)
return true;
return m_handlers.append(he);
return m_handlers.append(entry);
}
@ -548,12 +538,12 @@ bool sp_rcontext::handle_sql_condition(THD *thd,
DBUG_ASSERT(found_condition);
sp_handler_entry *handler_entry= NULL;
sp_instr_hpush_jump *handler_entry= NULL;
for (size_t i= 0; i < m_handlers.elements(); ++i)
{
sp_handler_entry *h= m_handlers.at(i);
sp_instr_hpush_jump *h= m_handlers.at(i);
if (h->handler == found_handler)
if (h->get_handler() == found_handler)
{
handler_entry= h;
break;
@ -582,7 +572,7 @@ bool sp_rcontext::handle_sql_condition(THD *thd,
// Mark active conditions so that they can be deleted when the handler exits.
da->mark_sql_conditions_for_removal();
uint continue_ip= handler_entry->handler->type == sp_handler::CONTINUE ?
uint continue_ip= handler_entry->get_handler()->type == sp_handler::CONTINUE ?
cur_spi->get_cont_dest() : 0;
/* End aborted result set. */
@ -601,7 +591,7 @@ bool sp_rcontext::handle_sql_condition(THD *thd,
new (callers_arena->mem_root) Handler_call_frame(cond_info, continue_ip);
m_handler_call_stack.append(frame);
*ip= handler_entry->first_ip;
*ip= handler_entry->m_ip + 1;
DBUG_RETURN(true);
}