Very slow inner join query Unacceptable latency.

<span style="font-family:Verdana; color:#000000; font-size:10pt;"><div>The SARS_ACTS table currently has 37,115,515
rows<br/><br />we have indexed: idx_sars_acts_acts_run_id ON SARS_ACTS USING btree (sars_run_id)<br />we have pk
constrainton the SARS_ACTS_RUN table; sars_acts_run_pkey PRIMARY KEY (id )<br /><br />serverdb=# explain select
count(*)as y0_ from SARS_ACTS this_ inner join SARS_ACTS_RUN tr1_ on this_.SARS_RUN_ID=<a
href="http://tr1_.ID">tr1_.ID</a>where tr1_.ALGORITHM='SMAT';<br />                                                   
QUERYPLAN<br
/>--------------------------------------------------------------------------------------------------------------------------<br
/>Aggregate (cost=4213952.17..4213952.18 rows=1 width=0)<br />  -> Hash Join  (cost=230573.06..4213943.93 rows=3296
width=0)<br/>       Hash Cond:  (this_.SARS_RUN_ID=<a href="http://tr1_.ID">tr1_.ID</a>)<br />       ->  Seq Scan om
sars_actsthis_  (cost=0.00..3844241.84 rows=37092284 width=8)<br />       ->  Hash  (cost=230565.81..230565.81
rows=580width=8)<br />              -> Seq Scan on sars_acts_run tr1_  (cost=0.00..230565.81 rows=580 width=8)<br
/>                  Filter:  ((algorithm)::text = 'SMAT'::text)<br />(7 rows)<br /><br />This query executes in
approximately5.3 minutes to complete, very very slow, our users are not happy.<br /><br />I did add an index on
SARS_ACTS_RUN.ALGORITHMcolumn but it didn't improve the run time. <br />The planner just changed the "Filter:" to an
"IndexScan:" improving the cost of the Seq Scan <br />on the sars_acts_run table, but the overall run time remained the
same.It seems like the bottleneck <br />is in the Seq Scan on the sars_acts table.<br /><br />              -> Seq
Scanon sars_acts_run tr1_  (cost=0.00..230565.81 rows=580 width=8)<br />                   Filter:  ((algorithm)::text
='SMAT'::text)<br /><br />Does anyone have suggestions about how to speed it up?<br /><a
href="mailto:pgsql-performance@postgresql.org"target="_blank"></a></div></span>