Re: No Index-Only Scan on Partial Index

On Tuesday, October 1, 2013, David E. Wheeler <<a href="mailto:david@justatheory.com">david@justatheory.com</a>>
wrote:<br/>> On Oct 1, 2013, at 3:56 PM, Merlin Moncure <<a
href="mailto:mmoncure@gmail.com">mmoncure@gmail.com</a>>wrote:<br /> ><br />>> I don't think it has
anythingto do with the conditional index -- it's<br />>> the functional based.  For some reason postgres always
wantsto post<br />>> filter (note the filter step below):<br /> >><br />>> postgres=# create index on
try(upper_inf(irange));<br/>>> CREATE INDEX<br />>> Time: 12.001 ms<br />>> postgres=# explain select
*from try where upper_inf(irange);<br />>>                                  QUERY PLAN<br /> >>
-------------------------------------------------------------------------------<br/>>> Index Scan using
try_upper_inf_idxon try  (cost=0.00..9.25 rows=33 width=40)<br />>>   Index Cond: (upper_inf(irange) = true)<br
/>>>   Filter: upper_inf(irange)<br />><br />> Hrm. I get a seq scan for that query:<br />><br />>
createindex on try(upper_inf(irange));<br />> explain select * from try where upper_inf(irange);<br />>          
             QUERY PLAN<br /> > -----------------------------------------------------------<br />>  Seq Scan on
try (cost=0.00..1887.00 rows=33333 width=68)<br />>    Filter: upper_inf(irange)<br />><br />> True also if I
justselect the irange. Is the filter the issue, here?<br /><br />Turn off seq scan...<br /><br />merlin