On Wed, Mar 23, 2011 at 11:58 AM, Adarsh Sharma <adarsh.sharma@xxxxxxxxxx> wrote:
Could you try just explaining the below query:
explain select distinct(p.crawled_page_id) from page_content p where NOT EXISTS (select 1 from clause2 c where c.source_id = p.crawled_page_id);
The idea here is to avoid directly using NOT operator.
Dear all,
I have 2 tables in my database name clause2( 4900 MB) & page_content(1582 MB).
My table definations are as :
page_content :-
CREATE TABLE page_content
(
content_id integer,
wkb_geometry geometry,
link_level integer,
isprocessable integer,
isvalid integer,
isanalyzed integer,
islocked integer,
content_language character(10),
url_id integer,
publishing_date character(40),
heading character(150),
category character(150),
crawled_page_url character(500),
keywords character(500),
dt_stamp timestamp with time zone,
"content" character varying,
crawled_page_id bigint,
id integer
)
WITH (
OIDS=FALSE
);
Indexes on it :-
CREATE INDEX idx_page_id ON page_content USING btree (crawled_page_id);
CREATE INDEX idx_page_id_content ON page_content USING btree (crawled_page_id, content_language, publishing_date, isprocessable);
CREATE INDEX pgweb_idx ON page_content USING gin (to_tsvector('english'::regconfig, content::text));
clause 2:-
CREATE TABLE clause2
(
id bigint NOT NULL DEFAULT nextval('clause_id_seq'::regclass),
source_id integer,
sentence_id integer,
clause_id integer,
tense character varying(30),
clause text,
CONSTRAINT pk_clause_demo_id PRIMARY KEY (id)
)WITH ( OIDS=FALSE);
Indexes on it :
CREATE INDEX idx_clause2_march10
ON clause2
USING btree
(id, source_id);
I perform a join query on it as :
explain analyze select distinct(p.crawled_page_id) from page_content p , clause2 c where p.crawled_page_id != c.source_id ;
What it takes more than 1 hour to complete. As I issue the explain analyze command and cannot able to wait for output but I send my explain output as :
QUERY PLAN
--------------------------------------------------------------------------------------------------------
Unique (cost=927576.16..395122387390.13 rows=382659 width=8)
-> Nested Loop (cost=927576.16..360949839832.15 rows=13669019023195 width=8)
Join Filter: (p.crawled_page_id <> c.source_id)
-> Index Scan using idx_page_id on page_content p (cost=0.00..174214.02 rows=428817 width=8)
-> Materialize (cost=927576.16..1370855.12 rows=31876196 width=4)
-> Seq Scan on clause2 c (cost=0.00..771182.96 rows=31876196 width=4)
(6 rows)
Please guide me how to make the above query run faster as I am not able to do that.
Thanks, Adarsh
Could you try just explaining the below query:
explain select distinct(p.crawled_page_id) from page_content p where NOT EXISTS (select 1 from clause2 c where c.source_id = p.crawled_page_id);
The idea here is to avoid directly using NOT operator.
Regards,
Chetan
--
Chetan Suttraway
EnterpriseDB, The Enterprise PostgreSQL company.
