am 03.05.2006, um 20:20:55 +0200 mailte Florian G. Pflug folgendes: > >of the index scan ? The table is quite big, might be possible. I still > >wonder why would be seqscan+sort faster than index scan... the sort will > >for sure have to write to disk too given the size of the table... > > When using an indexscan, postgres will read the actual rows in index-order, > rathen then in the order they appear on-disk. > For 200 million rows this means doing at least 200 million > disk seeks. Assuming that each seek takes just 1ms, thats > still amount to 200.000 seconds. Yepp, it is much cheaper to read the table seq and order later. Andreas -- Andreas Kretschmer (Kontakt: siehe Header) Heynitz: 035242/47215, D1: 0160/7141639 GnuPG-ID 0x3FFF606C http://wwwkeys.de.pgp.net === Schollglas Unternehmensgruppe ===
