Re: 7.2.1: coalesce double-calls function?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Kris Jurka <books(at)ejurka(dot)com>
Cc: SZŰCS Gábor <surrano(at)mailbox(dot)hu>, pgsql-general(at)postgresql(dot)org
Subject: Re: 7.2.1: coalesce double-calls function?
Date: 2003-02-04 18:26:15
Message-ID: 15607.1044383175@sss.pgh.pa.us
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Kris Jurka <books(at)ejurka(dot)com> writes:
> I have been looking at this and the NULLIF case seems complicatd.
> Essentially for NULLIF(left,right) I want to ExecEvalExpr(left,...)
> and construct a Const node with the result. Then makeSimpleA_Expr for
> const left = right.

Uh, no; you are confusing parse-time and run-time work. What you
probably want is a new node type that includes the OID of the
appropriate "=" operator but does different things with the result
than a normal "=" invocation would do.

Actually, thinking about it that way, it might just be a small variant
on the DistinctExpr node type that exists in current sources. Certainly
DistinctExpr would be a good model to look at.

regards, tom lane

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