Re: [HACKERS] Display number of heap accesses for index scans

2017-11-06 Thread Alexander Korotkov
On Mon, Nov 6, 2017 at 6:33 AM, Tom Lane wrote: > Peter Geoghegan writes: > > Andres Freund wrote: > >> The number of index lookups that failed to return anything can be a > >> critical performance factor in OLTP workloads. Therefore it

Re: [HACKERS] Display number of heap accesses for index scans

2017-11-05 Thread Tom Lane
Peter Geoghegan writes: > Andres Freund wrote: >> The number of index lookups that failed to return anything can be a >> critical performance factor in OLTP workloads. Therefore it seems like >> it'd be a good idea to extend the explain analyze output to

Re: [HACKERS] Display number of heap accesses for index scans

2017-11-05 Thread Peter Geoghegan
Andres Freund wrote: The number of index lookups that failed to return anything can be a critical performance factor in OLTP workloads. Therefore it seems like it'd be a good idea to extend the explain analyze output to include that information. I certainly agree. I've

[HACKERS] Display number of heap accesses for index scans

2017-11-04 Thread Andres Freund
Hi, right now it's hard to figure out whether a plain indexscan returns matches that then get eliminated due to visibility checks in the heap. For both index only scans (via "Heap Fetches") and bitmapscans (via row mismatches between bitmap heap and index scans) one can gather that to some degree