Reason of Slowness of query

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

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