Re: Why could different data in a table be processed with differentperformance?

On Mon, Sep 24, 2018 at 05:59:12PM -0700, Vladimir Ryabtsev wrote:
> > This seems significant..it means the heap was probably written in
> backwards
> order relative to the IDs, and the OS readahead is ineffective when index
> scanning across a range of IDs.
> But again, why is it different for one range and another? It was reversed
> for both ranges.

I don't have an explaination for it.. but I'd be curious to know
pg_stats.correlation for the id column:

SELECT schemaname, tablename, attname, correlation FROM pg_stats WHERE tablename='articles' AND column='article_id'
LIMIT1;
 

Justin