From: | "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> |
---|---|
To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | "Pavel Stehule" <pavel(dot)stehule(at)gmail(dot)com>, "Robert Haas" <robertmhaas(at)gmail(dot)com>, "Peter Eisentraut" <peter_e(at)gmx(dot)net>, "Jeff Davis" <pgsql(at)j-davis(dot)com>, "Greg Stark" <gsstark(at)mit(dot)edu>,<pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Patch for 8.5, transformationHook |
Date: | 2009-08-10 21:11:09 |
Message-ID: | 4A80469D02000025000297E8@gw.wicourts.gov |
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Lists: | pgsql-hackers |
Resending to correct a copy/paste error. Apologies.
"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> Yeah -- my argument would be that the = operator in NULLIF should be
> treated the same as if the function-like abbreviation were rewritten
> to the full CASE predicate. It doesn't surprise me that that is
> taken as text, given that they are both unadorned character string
> literals. The surprise here (for me at least) that the following
> generates a null of type text instead of matching the non-NULL input
> argument or (failing that) unknown, assuming the rewrite of
> NULLIF(a, b) to the equivalent CASE predicate:
>
> test=# select pg_typeof(case when null = 0 then null else null end);
> pg_typeof
> -----------
> text
> (1 row)
Symmetry fails here -- NULLIF is *not* treated the same as the CASE
predicate for which it is the abbreviation, which is arguably a
bug-level deviation from the SQL standard. Compare the above to:
test=# select pg_typeof(nullif(null, 0));
pg_typeof
-----------
integer
(1 row)
Which is the result I would want and expect, but is inconsistent with
treating it as an abbreviation of CASE.
-Kevin
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