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MDEV-334: Backport of UNION ALL optimization from mysql-5.7.

Browse Source 
Although the original code of mysql-5.7 was adjusted
to the current MariaDB code the main ideas of the optimization
were preserved.
This commit is contained in:
Igor Babaev
2014-10-14 09:36:50 -07:00
parent fec5ab5a56
commit 3c4bb0e872
31 changed files with 853 additions and 327 deletions
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76
sql/sql_select.cc
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@ -351,7 +351,7 @@ bool handle_select(THD *thd, LEX *lex, select_result *result,
else
{
SELECT_LEX_UNIT *unit= &lex->unit;
unit->set_limit(unit->global_parameters);
unit->set_limit(unit->global_parameters());
/*
'options' of mysql_select will be set in JOIN, as far as JOIN for
every PS/SP execution new, we will not need reset this flag if
@ -792,7 +792,8 @@ JOIN::prepare(Item ***rref_pointer_array,
ref_pointer_array= *rref_pointer_array;
/* Resolve the ORDER BY that was skipped, then remove it. */
if (skip_order_by && select_lex != select_lex->master_unit()->global_parameters)
if (skip_order_by && select_lex !=
select_lex->master_unit()->global_parameters())
{
if (setup_order(thd, (*rref_pointer_array), tables_list, fields_list,
all_fields, select_lex->order_list.first))
@ -2481,13 +2482,6 @@ void JOIN::exec_inner()
thd->set_examined_row_count(0);
DBUG_VOID_RETURN;
}
/*
Don't reset the found rows count if there're no tables as
FOUND_ROWS() may be called. Never reset the examined row count here.
It must be accumulated from all join iterations of all join parts.
*/
if (table_count)
thd->limit_found_rows= 0;
/*
Evaluate expensive constant conditions that were not evaluated during
@ -3091,7 +3085,6 @@ void JOIN::exec_inner()
*curr_fields_list),
Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF);
error= do_select(curr_join, curr_fields_list, NULL, procedure);
thd->limit_found_rows= curr_join->send_records;
if (curr_join->order && curr_join->filesort_found_rows)
{
/* Use info provided by filesort. */
@ -3257,7 +3250,7 @@ mysql_select(THD *thd, Item ***rref_pointer_array,
if (select_lex->linkage != GLOBAL_OPTIONS_TYPE)
{
//here is EXPLAIN of subselect or derived table
if (join->change_result(result))
if (join->change_result(result, NULL))
{
DBUG_RETURN(TRUE);
}
@ -12088,6 +12081,14 @@ return_zero_rows(JOIN *join, select_result *result, List<TABLE_LIST> &tables,
if (having && having->val_int() == 0)
send_row=0;
}
/* Update results for FOUND_ROWS */
if (!join->send_row_on_empty_set())
{
join->thd->set_examined_row_count(0);
join->thd->limit_found_rows= 0;
}
if (!(result->send_result_set_metadata(fields,
Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF)))
{
@ -12097,9 +12098,6 @@ return_zero_rows(JOIN *join, select_result *result, List<TABLE_LIST> &tables,
if (!send_error)
result->send_eof(); // Should be safe
}
/* Update results for FOUND_ROWS */
join->thd->limit_found_rows= 0;
join->thd->set_examined_row_count(0);
DBUG_RETURN(0);
}
@ -17300,6 +17298,9 @@ do_select(JOIN *join,List<Item> *fields,TABLE *table,Procedure *procedure)
if (error == NESTED_LOOP_QUERY_LIMIT)
error= NESTED_LOOP_OK; /* select_limit used */
}
join->thd->limit_found_rows= join->send_records;
if (error == NESTED_LOOP_NO_MORE_ROWS || join->thd->killed == ABORT_QUERY)
error= NESTED_LOOP_OK;
@ -23257,7 +23258,7 @@ int print_fake_select_lex_join(select_result_sink *result, bool on_the_fly,
/* rows */
item_list.push_back(item_null);
/* extra */
if (select_lex->master_unit()->global_parameters->order_list.first)
if (select_lex->master_unit()->global_parameters()->order_list.first)
item_list.push_back(new Item_string("Using filesort",
14, cs));
else
@ -23934,16 +23935,19 @@ bool mysql_explain_union(THD *thd, SELECT_LEX_UNIT *unit, select_result *result)
if (unit->is_union())
{
unit->fake_select_lex->select_number= FAKE_SELECT_LEX_ID; // jost for initialization
unit->fake_select_lex->type= "UNION RESULT";
unit->fake_select_lex->options|= SELECT_DESCRIBE;
if (unit->union_needs_tmp_table())
{
unit->fake_select_lex->select_number= FAKE_SELECT_LEX_ID; // just for initialization
unit->fake_select_lex->type= "UNION RESULT";
unit->fake_select_lex->options|= SELECT_DESCRIBE;
}
if (!(res= unit->prepare(thd, result, SELECT_NO_UNLOCK | SELECT_DESCRIBE)))
res= unit->exec();
}
else
{
thd->lex->current_select= first;
unit->set_limit(unit->global_parameters);
unit->set_limit(unit->global_parameters());
res= mysql_select(thd, &first->ref_pointer_array,
first->table_list.first,
first->with_wild, first->item_list,
@ -24427,28 +24431,34 @@ void st_select_lex::print(THD *thd, String *str, enum_query_type query_type)
/**
change select_result object of JOIN.
Change the select_result object of the JOIN.
@param res new select_result object
If old_result is not used, forward the call to the current
select_result in case it is a wrapper around old_result.
@retval
FALSE OK
@retval
TRUE error
Call prepare() and prepare2() on the new select_result if we decide
to use it.
@param new_result New select_result object
@param old_result Old select_result object (NULL to force change)
@retval false Success
@retval true Error
*/
bool JOIN::change_result(select_result *res)
bool JOIN::change_result(select_result *new_result, select_result *old_result)
{
DBUG_ENTER("JOIN::change_result");
result= res;
if (tmp_join)
tmp_join->result= res;
if (!procedure && (result->prepare(fields_list, select_lex->master_unit()) ||
result->prepare2()))
if (old_result == NULL || result == old_result)
{
DBUG_RETURN(TRUE);
result= new_result;
if (result->prepare(fields_list, select_lex->master_unit()) ||
result->prepare2())
DBUG_RETURN(true); /* purecov: inspected */
DBUG_RETURN(false);
}
DBUG_RETURN(FALSE);
else
DBUG_RETURN(result->change_result(new_result));
}