Matthew Wakeling <matthew@xxxxxxxxxxx> wrote: > On Fri, 17 Jul 2009, Kevin Grittner wrote: >> but a factor of 100? > The Java code runs all in RAM, versus Postgres running all from OS > cache or Postgres shared buffer (bit hard to tell which of those > two it is - there is no hard drive activity anyway). The Java code > does no page locking, whereas Postgres does loads. The Java code is > emulating just the index, whereas Postgres is fetching the whole row > as well. Oh, well, if you load all the data into Java's heap and are accessing it through HashMap or similar, I guess a factor of 100 is about right. I see the big difference as the fact that the Java implementation is dealing with everything already set up in RAM, versus needing to deal with a "disk image" format, even if it is cached. Try serializing those Java objects to disk and storing the file name in the HashMap, retrieving and de-serializing the object for each reference. Even if it's all cached, I expect you'd be running about 100 times slower. The Java heap isn't a very safe place to persist long-term data, however. -Kevin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
