Re: [HACKERS] generate_series regression 9.6->10 - Mailing list pgsql-hackers

From Tom Lane
Subject Re: [HACKERS] generate_series regression 9.6->10
Date
Msg-id 2634.1495646891@sss.pgh.pa.us
Whole thread Raw
In response to [HACKERS] generate_series regression 9.6->10  (Paul Ramsey <pramsey@cleverelephant.ca>)
Responses Re: [HACKERS] generate_series regression 9.6->10
List pgsql-hackers
Paul Ramsey <pramsey@cleverelephant.ca> writes:
> The behaviour of generate_series seems to have changed a little, at least
> in conjunction w/ CTEs.

What's changed is the behavior of multiple SRFs in a SELECT's targetlist,
cf

https://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=69f4b9c85f168ae006929eec44fc44d569e846b9

specifically this comment:
   While moving SRF evaluation to ProjectSet would allow to retain the old   "least common multiple" behavior when
multipleSRFs are present in one   targetlist (i.e.  continue returning rows until all SRFs are at the end of   their
inputat the same time), we decided to instead only return rows till   all SRFs are exhausted, returning NULL for
alreadyexhausted ones.  We   deemed the previous behavior to be too confusing, unexpected and actually   not
particularlyuseful.
 

I see the current v10 release notes have failed miserably at documenting
this :-(.  Will try to improve that.
        regards, tom lane



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