Bruce Momjian wrote: > Ron Mayer wrote: >> Bruce Momjian wrote: >>> Oleg Bartunov wrote: >>>> What is a basis of your assumption ? >> I think I asked about this kind of usage a couple years back;... >> >> http://archives.postgresql.org/pgsql-general/2005-10/msg00475.php >> http://archives.postgresql.org/pgsql-general/2005-10/msg00477.php >> >> ...why the functional index was >> slower than maintaining the extra column; with the explanation >> that the lossy index having to call the function (including >> parsing, dictionary lookup, etc) for re-checking the data ... >> ... >>> >>> Are you saying the majority of users have a separate column with a >>> trigger? >> I think so. At least when I was using it in 2005 the second >> column with the trigger was faster than using a functional index. > > OK, it is good you measured it. I wonder how GIN would behave because > it is not lossy.
Too bad I don't have the same database around anymore. It seems the re-parsing for re-checking for the lossy index was very expensive, tho. In the end, I suspect it depends greatly on what fraction of rows match. >>>> We need more feedback from users. >>> Well, I am waiting for other hackers to get involved, but if they don't, >>> I have to evaluate it myself on the email lists. >> Personally, I think documentation changes would be an OK way to >> to handle it. Something that makes it extremely clear to the >> user the advantages of having the extra column and the risks >> of avoiding them. > > Sure, but you have make sure you use the right configuration in the > trigger, no? Does the tsquery have to use the same configuration? I wish I knew this myself. :-) Whatever I had done happened to work but that was largely through people on IRC walking me through it. ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings