On Sat, Oct 1, 2011 at 2:30 PM, Jeff Adams <jeff.ad...@noaa.gov> wrote: > Greetings, > > I have a large table (~19 million records). Records contains a field > identifying a vessel and a field containing an time (epoch). Using the > current rows vessel and time values, I need to be able to find the next > lowest time value for the vessel and use it to compute how much time has > elapsed between the records. I have tried a scalar subquery in the SELECT, > which works, but it runs quite slowly. Is there an alternative approach that > might perform better for this type of query. Any information would be > greatly appreciated. Thanks... > How many rows per vessel?
Either way it seems to me we are talking about selecting the current record, and then selecting the max of another record within a timeframe. I would probably use a plpgsql function that would do this in two stages, ideally being able to do an index scan twice.... Best Wishes, Chris Travers -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
