Commit d33ac37b authored by unknown's avatar unknown
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BUG#15935: In mysql_update, don't use full index scan when we could have used quick select scan. 


mysql-test/r/update.result:
  Testcase for BUG#15935
mysql-test/t/update.test:
  Testcase for BUG#15935
sql/sql_update.cc:
  BUG#15935: 
  - Do account for the fact that used_index!=MAX_KEY is also true for cases
    when quick select is used, and use quick select then (and not full index scan).
  - Also removed the redundant "used_index= MAX_KEY" statement
parent 52ff597a

mysql-test/r/update.result

+15 −0
Original line number Diff line number Diff line
@@ -358,3 +358,18 @@ update t2,t1 set f1=3,f2=3 where f1=f2 and f1=1; 
affected rows: 3

info: Rows matched: 3  Changed: 3  Warnings: 0

drop table t1,t2;

create table t1 (a int);

insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);

create table t2 (a int, filler1 char(200), filler2 char(200), key(a));

insert into t2 select A.a + 10*B.a, 'filler','filler' from t1 A, t1 B;

flush status;

update t2 set a=3 where a=2;

show status like 'handler_read%';

Variable_name	Value

Handler_read_first	0

Handler_read_key	1

Handler_read_next	1

Handler_read_prev	0

Handler_read_rnd	1

Handler_read_rnd_next	0

drop table t1, t2;

mysql-test/t/update.test

+12 −0
Original line number Diff line number Diff line
@@ -287,4 +287,16 @@ update t1 set f1=1 where f1=3; 
update t2,t1 set f1=3,f2=3 where f1=f2 and f1=1;

--disable_info

drop table t1,t2;





# BUG#15935

create table t1 (a int);

insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);

create table t2 (a int, filler1 char(200), filler2 char(200), key(a));

insert into t2 select A.a + 10*B.a, 'filler','filler' from t1 A, t1 B;

flush status;

update t2 set a=3 where a=2;

show status like 'handler_read%';

drop table t1, t2;



# End of 4.1 tests

sql/sql_update.cc

+1 −2
Original line number Diff line number Diff line
@@ -212,7 +212,6 @@ int mysql_update(THD *thd, 
      SORT_FIELD  *sortorder;

      ha_rows examined_rows;



      used_index= MAX_KEY;                   // For call to init_read_record()

      table->sort.io_cache = (IO_CACHE *) my_malloc(sizeof(IO_CACHE),

						    MYF(MY_FAE | MY_ZEROFILL));

      if (!(sortorder=make_unireg_sortorder(order, &length)) ||
@@ -244,7 +243,7 @@ int mysql_update(THD *thd, 
			   DISK_BUFFER_SIZE, MYF(MY_WME)))

	goto err;



      if (used_index == MAX_KEY)

      if (used_index == MAX_KEY || (select && select->quick))

        init_read_record(&info,thd,table,select,0,1);

      else

        init_read_record_idx(&info, thd, table, 1, used_index);