> From: [EMAIL PROTECTED] 
> [mailto:[EMAIL PROTECTED] On Behalf Of 
> Dan Harris
> 
> After some digging, I've found that the planner is choosing 
> to apply a necessary seq scan to the table.  Unfortunately,
> it's scanning the whole table, when it seems that it could 
> have joined it to a smaller table first and reduce the
> amount of rows it would have to scan dramatically ( 70 
> million to about 5,000 ).
> 

Joining will reduce the amount of rows to scan for the filter, but
performing the join is non-trivial.  If postgres is going to join two tables
together without applying any filter first then it will have to do a seqscan
of one of the tables, and if it chooses the table with 5000 rows, then it
will have to do 5000 index scans on a table with 70 million records.  I
don't know which way would be faster. 

I wonder if you could find a way to use an index to do the text filter.
Maybe tsearch2?  I haven't used anything like that myself, maybe someone
else has more input.


---------------------------(end of broadcast)---------------------------
TIP 1: if posting/reading through Usenet, please send an appropriate
       subscribe-nomail command to [EMAIL PROTECTED] so that your
       message can get through to the mailing list cleanly

Reply via email to