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-rw-r--r--sql/sql_select.cc64
1 files changed, 38 insertions, 26 deletions
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 2f417fc2618..cd6ff415070 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -104,7 +104,7 @@ static COND *make_cond_for_table(COND *cond,table_map table,
static Item* part_of_refkey(TABLE *form,Field *field);
static uint find_shortest_key(TABLE *table, key_map usable_keys);
static bool test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,
- ha_rows select_limit);
+ ha_rows select_limit, bool no_changes);
static int create_sort_index(JOIN_TAB *tab,ORDER *order,ha_rows select_limit);
static int remove_duplicates(JOIN *join,TABLE *entry,List<Item> &fields);
static int remove_dup_with_compare(THD *thd, TABLE *entry, Field **field,
@@ -154,7 +154,7 @@ mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &fields,COND *conds,
TABLE *tmp_table;
int error,tmp;
bool need_tmp,hidden_group_fields;
- bool simple_order,simple_group,no_order;
+ bool simple_order,simple_group,no_order, skip_sort_order;
Item::cond_result cond_value;
SQL_SELECT *select;
DYNAMIC_ARRAY keyuse;
@@ -169,7 +169,7 @@ mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &fields,COND *conds,
select_distinct=test(select_options & SELECT_DISTINCT);
tmp_table=0;
select=0;
- no_order=0;
+ no_order=skip_sort_order=0;
bzero((char*) &keyuse,sizeof(keyuse));
thd->proc_info="init";
thd->used_tables=0; // Updated by setup_fields
@@ -433,8 +433,10 @@ mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &fields,COND *conds,
select_distinct=0;
}
else if (select_distinct && join.tables - join.const_tables == 1 &&
- (order || thd->select_limit == HA_POS_ERROR ||
- (join.select_options & OPTION_FOUND_ROWS)))
+ (thd->select_limit == HA_POS_ERROR ||
+ (join.select_options & OPTION_FOUND_ROWS) ||
+ order &&
+ !(skip_sort_order=test_if_skip_sort_order(&join.join_tab[join.const_tables], order, thd->select_limit,1))))
{
if ((group=create_distinct_group(order,fields)))
{
@@ -518,7 +520,7 @@ mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &fields,COND *conds,
if (!(select_options & SELECT_BIG_RESULT) &&
((group && join.const_tables != join.tables &&
!test_if_skip_sort_order(&join.join_tab[join.const_tables], group,
- HA_POS_ERROR)) ||
+ thd->select_limit,0)) ||
select_distinct) &&
join.tmp_table_param.quick_group && !procedure)
{
@@ -532,10 +534,9 @@ mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &fields,COND *conds,
if (order &&
(join.const_tables == join.tables ||
test_if_skip_sort_order(&join.join_tab[join.const_tables], order,
- (having || group ||
- join.const_tables != join.tables - 1 ||
+ (join.const_tables != join.tables - 1 ||
(join.select_options & OPTION_FOUND_ROWS)) ?
- HA_POS_ERROR : thd->select_limit)))
+ HA_POS_ERROR : thd->select_limit,0)))
order=0;
select_describe(&join,need_tmp,
(order != 0 &&
@@ -571,7 +572,7 @@ mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &fields,COND *conds,
group : (ORDER*) 0),
group ? 0 : select_distinct,
group && simple_group,
- order == 0 &&
+ (order == 0 || skip_sort_order) &&
!(join.select_options & OPTION_FOUND_ROWS),
join.select_options)))
goto err; /* purecov: inspected */
@@ -622,6 +623,13 @@ mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &fields,COND *conds,
break;
join_tab->not_used_in_distinct=1;
} while (join_tab-- != join.join_tab);
+ /* Optimize "select distinct b from t1 order by key_part_1 limit #" */
+ if (order && skip_sort_order)
+ {
+ (void) test_if_skip_sort_order(&join.join_tab[join.const_tables],
+ order, thd->select_limit,0);
+ order=0;
+ }
}
/* Copy data to the temporary table */
@@ -4757,15 +4765,15 @@ end_write(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
if (create_myisam_from_heap(table, &join->tmp_table_param, error,1))
DBUG_RETURN(1); // Not a table_is_full error
table->uniques=0; // To ensure rows are the same
- if (++join->send_records >= join->tmp_table_param.end_write_records &
- join->do_send_rows)
- {
- if (!(join->select_options & OPTION_FOUND_ROWS))
- DBUG_RETURN(-3);
- join->do_send_rows=0;
- join->thd->select_limit = HA_POS_ERROR;
- DBUG_RETURN(0);
- }
+ }
+ if (++join->send_records >= join->tmp_table_param.end_write_records &
+ join->do_send_rows)
+ {
+ if (!(join->select_options & OPTION_FOUND_ROWS))
+ DBUG_RETURN(-3);
+ join->do_send_rows=0;
+ join->thd->select_limit = HA_POS_ERROR;
+ DBUG_RETURN(0);
}
}
}
@@ -5162,7 +5170,8 @@ static uint find_shortest_key(TABLE *table, key_map usable_keys)
/* Return 1 if we don't have to do file sorting */
static bool
-test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit)
+test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit,
+ bool no_changes)
{
int ref_key;
TABLE *table=tab->table;
@@ -5217,11 +5226,14 @@ test_if_skip_sort_order(JOIN_TAB *tab,ORDER *order,ha_rows select_limit)
int flag;
if ((flag=test_if_order_by_key(order,table,nr)))
{
- tab->index=nr;
- tab->read_first_record= (flag > 0 ? join_init_read_first_with_key:
- join_init_read_last_with_key);
- table->file->index_init(nr);
- tab->type=JT_NEXT; // Read with index_first(), index_next()
+ if (!no_changes)
+ {
+ tab->index=nr;
+ tab->read_first_record= (flag > 0 ? join_init_read_first_with_key:
+ join_init_read_last_with_key);
+ table->file->index_init(nr);
+ tab->type=JT_NEXT; // Read with index_first(), index_next()
+ }
DBUG_RETURN(1);
}
}
@@ -5239,7 +5251,7 @@ create_sort_index(JOIN_TAB *tab,ORDER *order,ha_rows select_limit)
SQL_SELECT *select=tab->select;
DBUG_ENTER("create_sort_index");
- if (test_if_skip_sort_order(tab,order,select_limit))
+ if (test_if_skip_sort_order(tab,order,select_limit,0))
DBUG_RETURN(0);
if (!(sortorder=make_unireg_sortorder(order,&length)))
goto err; /* purecov: inspected */
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