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Fix bug mdev-447: Wrong output from the EXPLAIN command of the test case for lp bug #714999

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The fix backports from MWL#182: Explain running statements the logic that
saves the original JOIN_TAB array of a query plan after optimization. This
array is later used during EXPLAIN to iterate over the original JOIN plan
nodes in the cases when this plan could be changed by early subquery
execution during the optimization phase of the outer query.
This commit is contained in:
unknown
2012-08-21 15:24:43 +03:00
parent a45c451e40
commit 80b3f74705
9 changed files with 52 additions and 31 deletions
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54
sql/sql_select.cc
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@@ -271,8 +271,11 @@ Item_equal *find_item_equal(COND_EQUAL *cond_equal, Field *field,
bool *inherited_fl);
JOIN_TAB *first_depth_first_tab(JOIN* join);
JOIN_TAB *next_depth_first_tab(JOIN* join, JOIN_TAB* tab);
JOIN_TAB *first_breadth_first_tab(JOIN *join);
JOIN_TAB *next_breadth_first_tab(JOIN *join, JOIN_TAB *tab);
enum enum_exec_or_opt {WALK_OPTIMIZATION_TABS , WALK_EXECUTION_TABS};
JOIN_TAB *first_breadth_first_tab(JOIN *join, enum enum_exec_or_opt tabs_kind);
JOIN_TAB *next_breadth_first_tab(JOIN *join, enum enum_exec_or_opt tabs_kind,
JOIN_TAB *tab);
/**
This handles SELECT with and without UNION.
@@ -6649,12 +6652,12 @@ double JOIN::get_examined_rows()
{
ha_rows examined_rows;
double prev_fanout= 1;
JOIN_TAB *tab= first_breadth_first_tab(this);
JOIN_TAB *tab= first_breadth_first_tab(this, WALK_OPTIMIZATION_TABS);
JOIN_TAB *prev_tab= tab;
examined_rows= tab->get_examined_rows();
while ((tab= next_breadth_first_tab(this, tab)))
while ((tab= next_breadth_first_tab(this, WALK_OPTIMIZATION_TABS, tab)))
{
prev_fanout *= prev_tab->records_read;
examined_rows+= (ha_rows) (tab->get_examined_rows() * prev_fanout);
@@ -7269,23 +7272,30 @@ prev_record_reads(POSITION *positions, uint idx, table_map found_ref)
Enumerate join tabs in breadth-first fashion, including const tables.
*/
JOIN_TAB *first_breadth_first_tab(JOIN *join)
JOIN_TAB *first_breadth_first_tab(JOIN *join, enum enum_exec_or_opt tabs_kind)
{
return join->join_tab; /* There's always one (i.e. first) table */
/* There's always one (i.e. first) table */
return (tabs_kind == WALK_EXECUTION_TABS)? join->join_tab:
join->table_access_tabs;
}
JOIN_TAB *next_breadth_first_tab(JOIN *join, JOIN_TAB *tab)
JOIN_TAB *next_breadth_first_tab(JOIN *join, enum enum_exec_or_opt tabs_kind,
JOIN_TAB *tab)
{
JOIN_TAB* const first_top_tab= first_breadth_first_tab(join, tabs_kind);
const uint n_top_tabs_count= (tabs_kind == WALK_EXECUTION_TABS)?
join->top_join_tab_count:
join->top_table_access_tabs_count;
if (!tab->bush_root_tab)
{
/* We're at top level. Get the next top-level tab */
tab++;
if (tab < join->join_tab + join->top_join_tab_count)
if (tab < first_top_tab + n_top_tabs_count)
return tab;
/* No more top-level tabs. Switch to enumerating SJM nest children */
tab= join->join_tab;
tab= first_top_tab;
}
else
{
@@ -7309,7 +7319,7 @@ JOIN_TAB *next_breadth_first_tab(JOIN *join, JOIN_TAB *tab)
Ok, "tab" points to a top-level table, and we need to find the next SJM
nest and enter it.
*/
for (; tab < join->join_tab + join->top_join_tab_count; tab++)
for (; tab < first_top_tab + n_top_tabs_count; tab++)
{
if (tab->bush_children)
return tab->bush_children->start;
@@ -7333,7 +7343,7 @@ JOIN_TAB *first_top_level_tab(JOIN *join, enum enum_with_const_tables with_const
JOIN_TAB *next_top_level_tab(JOIN *join, JOIN_TAB *tab)
{
tab= next_breadth_first_tab(join, tab);
tab= next_breadth_first_tab(join, WALK_EXECUTION_TABS, tab);
if (tab && tab->bush_root_tab)
tab= NULL;
return tab;
@@ -7633,6 +7643,12 @@ get_best_combination(JOIN *join)
join->top_join_tab_count= join->join_tab_ranges.head()->end -
join->join_tab_ranges.head()->start;
/*
Save pointers to select join tabs for SHOW EXPLAIN
*/
join->table_access_tabs= join->join_tab;
join->top_table_access_tabs_count= join->top_join_tab_count;
update_depend_map(join);
DBUG_RETURN(0);
}
@@ -21389,8 +21405,8 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
bool printing_materialize_nest= FALSE;
uint select_id= join->select_lex->select_number;
for (JOIN_TAB *tab= first_breadth_first_tab(join); tab;
tab= next_breadth_first_tab(join, tab))
for (JOIN_TAB *tab= first_breadth_first_tab(join, WALK_OPTIMIZATION_TABS); tab;
tab= next_breadth_first_tab(join, WALK_OPTIMIZATION_TABS, tab))
{
if (tab->bush_root_tab)
{
@@ -21473,16 +21489,8 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
else
{
TABLE_LIST *real_table= table->pos_in_table_list;
/*
Internal temporary tables have no corresponding table reference
object. Such a table may appear in EXPLAIN when a subquery that needs
a temporary table has been executed, and JOIN::exec replaced the
original JOIN with a plan to access the data in the temp table
(made by JOIN::make_simple_join).
*/
const char *tab_name= real_table ? real_table->alias :
"internal_tmp_table";
item_list.push_back(new Item_string(tab_name, strlen(tab_name), cs));
item_list.push_back(new Item_string(real_table->alias,
strlen(real_table->alias), cs));
}
/* "partitions" column */
if (join->thd->lex->describe & DESCRIBE_PARTITIONS)