On Wed, Jun 21, 2006 at 04:12:08PM +0200, Alban Hertroys wrote: > Martijn van Oosterhout wrote: > >ISTM that what would really work well is some kind of "Merge Sort" node > >that would work by having multiple subnodes which are already sorted > >and merging them into one sorted list. > > Would... So this isn't available yet? Not AFAIK. > >It would push the ORDER BY down to the subqueries and then merge the > >results. If the subqueries can be read efficiently sorted (via an index > >for example) then you would get very quick output, especially if you > >have a LIMIT clause. > > I just realized that OFFSET kind of complicates the problem. > > If PostgreSQL would handle this (for inheritance as well, I hope), it'd > need to keep track of how many records came from which tables to set the > offsets in the subqueries appropriately, which of course depends on the > previous query... Well, I said it complicates things... OFFSET is not a problem at all. It's just code for "throw away first N rows". Once you have the above node type, the executor would simply throw away somed rows, whichever table they came from. Have a nice day, -- Martijn van Oosterhout <kleptog@xxxxxxxxx> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to litigate.
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