Re: Performance degradation in Bitmapscan (commit 75ae538bc3168bf44475240d4e0487ee2f3bb376)

Hi Dilip,

thanks for noticing that one.

On 2016-11-09 21:17:22 +0530, Dilip Kumar wrote:
> While testing bitmap performance, I have observed that some of the
> TPCH queries taking huge time in BitmapIndexScan node, when there are
> lossy pages.

It's not really related to lossy pages, it's just that due to deletions
/ insertions a lot more "shapes" of the hashtable are hit.

I suspect that this is with parallelism disabled? Without that the query
ends up using a parallel sequential scan for me.


I've a working fix for this, and for a similar issue Robert found. I'm
still playing around with it, but basically the fix is to make the
growth policy a bit more adaptive.

Greetings,

Andres Freund