Views do not help or hurt performance. Views encapsulate complex queries.
If you have a slow running query, the usual way to get help is to post:
*) explain analyze results (most important)
*) the query (important)
*) interesting tables/indexes (somewhat important)
----------------------
These are 2 queries for example...
The first runs with 55ms, the 2nd with views is executed in 4500ms...
:confused:
SELECT DISTINCT table_0.term1, table_1.term2 FROM TC table_0 , TO table_1
WHERE table_1.term1='c' AND table_0.term2=table_1.term2
UNION
SELECT DISTINCT table_0.term1, table_1.term1 FROM TC table_0 , TB table_1
WHERE table_0.term2=table_1.term1 AND table_1.term2='c'
----------------------------------------------------------
SELECT DISTINCT V2TC.term1 AS term1,V2TO.term2 AS term2
FROM V2TO,V2TC
WHERE V2TO.term2=V2TC.term2 AND V2TO.term1='c'
---------Definition of tables and views involved-------------
-- Table: TC
CREATE TABLE TC(
term1 character varying(100),
term2 character varying(100)
)
WITH (OIDS=FALSE);
ALTER TABLE TC OWNER TO postgres;
-- Index: TC_index1
CREATE INDEX TC_index1
ON TC
USING btree
(term1);
-- Index: TC_index2
CREATE INDEX TC_index2
ON TC
USING btree
(term2);
--TO and TB are more or less equal to TC
-- View: v2TC
CREATE OR REPLACE VIEW v2TC AS
SELECT DISTINCT TC.term1, TC.term2
FROM TC
ORDER BY TC.term1, TC.term2;
ALTER TABLE v2TC OWNER TO postgres;
-- View: v2TO
CREATE OR REPLACE VIEW v2TO AS ( SELECT DISTINCT TO.term1, TO.term2
FROM TO
ORDER BY TO.term1, TO.term2)
UNION
SELECT TB.term2 AS term1, TB.term1 AS term2
FROM TB;
ALTER TABLE v2TO OWNER TO postgres;
--
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