Update of table using WHERE id = <cursor>.<id> ignores index on field ID
------------------------------------------------------------------------
Key: CORE-4675
URL: http://tracker.firebirdsql.org/browse/CORE-4675
Project: Firebird Core
Issue Type: Bug
Components: Engine
Reporter: Pavel Zotov
DDL:
====
recreate table ttt(id int primary key using index pk_ttt_id, x int, y int);
commit;
insert into ttt select row_number()over(), rand()*10, rand()*100 from
rdb$types, rdb$types rows 10000;
commit;
create index ttt_x on ttt(x);
commit;
Test-1 (fast):
==========
set term ^;
execute block as
declare a_x int;
declare v_id int;
declare v_x int;
declare v_y int;
declare c_upd cursor for (select id, x, y from ttt where x = :a_x);
begin
a_x = 5;
open c_upd;
while (1=1) do begin
fetch c_upd into v_id, v_x, v_y;
if (row_count = 0) then leave;
update ttt v set y = c_upd.x, x = c_upd.y
where v.id = :v_id; ------------------------------ ::: key is specified by
VARIABLE which has value from FETCH statement
end
close c_upd;
end
^ set term ;^
rollback;
Trace-1:
======
Select Expression
-> Filter
-> Table "TTT" as "C_UPD TTT" Access By ID
-> Bitmap
-> Index "TTT_X" Range Scan (full match)
Select Expression
-> Filter
-> Table "TTT" as "V" Access By ID
-> Bitmap
-> Index "PK_TTT_ID" Unique Scan
0 records fetched
26 ms, 165 read(s), 15 write(s), 18741 fetch(es), 3034 mark(s)
Table Natural Index Update Insert
************************************************************************
RDB$INDICES 14
RDB$RELATION_CONSTRAINTS 200
TTT 2016 1008
Test-2 (VERY slow):
===============
set term ^;
execute block as
declare a_x int;
declare v_id int;
declare v_x int;
declare v_y int;
declare c_upd cursor for (select id, x, y from ttt where x = :a_x);
begin
a_x = 5;
open c_upd;
while (1=1) do begin
fetch c_upd; -- into v_id, v_x, v_y;
if (row_count = 0) then leave;
update ttt v set y = c_upd.x, x = c_upd.y
where v.id = c_upd.id; --------------------------------- ::: key is
specified by CURSOR field using "cursor name + dot + field" syntax
end
close c_upd;
end
^ set term ;^
rollback;
Trace-2:
=======
Select Expression
-> Filter
-> Table "TTT" as "C_UPD TTT" Access By ID
-> Bitmap
-> Index "TTT_X" Range Scan (full match)
Select Expression
-> Filter
-> Table "TTT" as "V" Full Scan
0 records fetched
8669 ms, 20317223 fetch(es), 3015 mark(s)
Table Natural Index Update
**************************************************************
TTT 10080000 1008 1008
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