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Hi, I am seeing a performance problem with postgresql v 11.7 on views, and I am wondering if anyone can tell me why or has any suggestion. A table is created as: CREATE TABLE "FBNK_CUSTOMER" (RECID VARCHAR(255) NOT NULL
PRIMARY KEY, XMLRECORD VARCHAR) And contains only 180 rows. Doing an explain plan on the view created over this gives: EXPLAIN
ANALYZE select RECID
from
"V_FBNK_CUSTOMER" Subquery Scan on "V_FBNK_CUSTOMER" (cost=0.00..19014.60 rows=180 width=7) (actual time=459.601..78642.189 rows=180 loops=1) -> Seq Scan on "FBNK_CUSTOMER" a (cost=0.00..19012.80 rows=180 width=14575) (actual time=459.600..78641.950 rows=180 loops=1) Planning Time: 0.679 ms Execution Time: 78642.616 ms Yet an Explain plan on the underlying table( on select RECID from “FBNK_CUSTOMER”) gives: Seq Scan on "FBNK_CUSTOMER" (cost=0.00..22.80 rows=180 width=7) (actual time=0.004..0.272 rows=180 loops=1) Planning Time: 0.031 ms Execution Time: 0.288 ms So you can see that postgresql is not using the primary key index for RECID.
THIS IS NOT THE CASE FOR ORACLE where the primary key index is used in the explain plan The view is created similar to the following where extractValueJS is a stored procedure that extracts a value from the VARCHAR XMLRECORD column. CREATE VIEW "V_FBNK_CUSTOMER" as
SELECT a.RECID, a.XMLRECORD "THE_RECORD" ,a.RECID "CUSTOMER_CODE" ,a.RECID "CUSTOMER_NO" ,extractValueJS(a.XMLRECORD, 1, 0) "MNEMONIC" ,extractValueJS(a.XMLRECORD, 2, 0) "SHORT_NAME" ,extractValueJS(a.XMLRECORD, 2, -1) "SHORT_NAME_2" , etc ,
extractValueJS(a.XMLRECORD, 179, 9) "TESTER" FROM "FBNK_CUSTOMER" a As well, the problem gets worse as columns are added to the view,
irrespective of the SELECTION columns and it seems to perform some activity behind. Creating an empty view, CREATE
VIEW
"V_FBNK_CUSTOMER_TEST"
as
SELECT a.RECID, a.XMLRECORD
"THE_RECORD" ,a.RECID
"CUSTOMER_CODE" ,a.RECID
"CUSTOMER_NO" FROM
"FBNK_CUSTOMER" a ------------- > 3 ms
select RECID
from
"V_FBNK_CUSTOMER_TEST"
CREATE
VIEW
"V_FBNK_CUSTOMER_TEST"
as
SELECT a.RECID, a.XMLRECORD
"THE_RECORD" ,a.RECID
"CUSTOMER_CODE" ,a.RECID
"CUSTOMER_NO" ,extractValueJS(a.XMLRECORD,
1,
0)
"MNEMONIC" FROM
"FBNK_CUSTOMER" a ----------------à
54 ms select RECID
from
"V_FBNK_CUSTOMER_TEST" CREATE
VIEW
"V_FBNK_CUSTOMER_TEST"
as
SELECT a.RECID, a.XMLRECORD
"THE_RECORD" ,a.RECID
"CUSTOMER_CODE" ,a.RECID
"CUSTOMER_NO" ,extractValueJS(a.XMLRECORD,
1,
0)
"MNEMONIC" ,extractValueJS(a.XMLRECORD,
2,
0)
"SHORT_NAME" FROM
"FBNK_CUSTOMER" a ----------------------à
118 ms select RECID
from
"V_FBNK_CUSTOMER_TEST" The following query takes an extremely long time for only 180 rows, and what this means is that we would have to index anything appearing in the where clause
for every table in order to use views because the views seem not to consider the select clause. Why is that and does anyone know a way around this? SELECT RECID
FROM
"V_FBNK_CUSTOMER"
WHERE
"TESTER" =
'5.00'
ORDER
BY RECID Sort (cost=19015.06..19015.06 rows=1 width=7) (actual time=102172.500..102172.501 rows=1 loops=1) Sort Key: "V_FBNK_CUSTOMER".recid Sort Method: quicksort Memory: 25kB -> Subquery Scan on "V_FBNK_CUSTOMER" (cost=0.00..19015.05 rows=1 width=7) (actual time=91242.866..102172.474 rows=1 loops=1) Filter: (("V_FBNK_CUSTOMER"."TESTER")::text = '5.00'::text) Rows Removed by Filter: 179 -> Seq Scan on "FBNK_CUSTOMER" a (cost=0.00..19012.80 rows=180 width=14575) (actual time=613.455..102172.175 rows=180 loops=1) Planning Time: 1.674 ms Execution Time: 102174.015 ms The information in this e-mail and any attachments is confidential and may be legally privileged. It is intended solely for the addressee or addressees. Any use or disclosure of the contents of this e-mail/attachments by a not intended recipient is unauthorized and may be unlawful. If you have received this e-mail in error please notify the sender. Please note that any views or opinions presented in this e-mail are solely those of the author and do not necessarily represent those of TEMENOS. We recommend that you check this e-mail and any attachments against viruses. TEMENOS accepts no liability for any damage caused by any malicious code or virus transmitted by this e-mail. |
