2013/5/15 Robert Haas <robertmhaas@xxxxxxxxx>
I was playing with the query a while ago and put it aside since then,
--
Victor Y. Yegorov
Apologies for resurrecting an old thread, but I just came across this> Original query looks like this ( http://explain.depesz.com/s/pzv ):
>
> After a while I added row_number() to the inner part (
> http://explain.depesz.com/s/hfs ):
>
> It was really surprising to see a "side" effect of 8x performance boost.
> The only difference I can see is an extra WindowAgg step in the second variant.
post while doing some research and I don't see any responses.
This seems like a mighty interesting example. I'm not sure what's
going on here, but let me guess. I think that the WindowAgg is
forcing some operation - detoasting, maybe? - to happen under the
materialize node. As a result, it only gets done once. But in the
other plan, the detoast happens at the nested loop level, above the
materialize node, and therefore it happens 10x instead of 1x.
need time to come back to this thing.
I will try to put together a testcase for this example, I'd like to achieve
the same behavior on a non-GIS data set.
Victor Y. Yegorov
