From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
Cc: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Craig Ringer <craig(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: patch: function xmltable |
Date: | 2017-01-25 00:35:11 |
Message-ID: | 20170125003511.zc3kzwiio7kpntda@alap3.anarazel.de |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On 2017-01-24 21:32:56 -0300, Alvaro Herrera wrote:
> Andres Freund wrote:
> > Hi,
> >
> > On 2017-01-24 17:38:49 -0300, Alvaro Herrera wrote:
> > > +static Datum ExecEvalTableExpr(TableExprState *tstate, ExprContext *econtext,
> > > + bool *isnull);
> > > +static Datum ExecEvalTableExprFast(TableExprState *exprstate, ExprContext *econtext,
> > > + bool *isNull);
> > > +static Datum tabexprFetchRow(TableExprState *tstate, ExprContext *econtext,
> > > + bool *isNull);
> > > +static void tabexprInitialize(TableExprState *tstate, ExprContext *econtext,
> > > + Datum doc);
> > > +static void ShutdownTableExpr(Datum arg);
> >
> > To me this (and a lot of the other code) hints quite strongly that
> > expression evalution is the wrong approach to implementing this. What
> > you're essentially doing is building a vulcano style scan node. Even if
> > we can this, we shouldn't double down on the bad decision to have these
> > magic expressions that return multiple rows. There's historical reason
> > for tSRFs, but we shouldn't add more weirdness like this.
>
> Thanks for giving it a look. I have long thought that this patch would
> be at odds with your overall executor work.
Not fundamentally, but it makes it harder.
> XMLTABLE is specified by the standard to return multiple rows ... but
> then as far as my reading goes, it is only supposed to be supported in
> the range table (FROM clause) not in the target list. I wonder if
> this would end up better if we only tried to support it in RT. I asked
> Pavel to implement it like that a few weeks ago, but ...
Right - it makes sense in the FROM list - but then it should be an
executor node, instead of some expression thingy.
Greetings,
Andres Freund
From | Date | Subject | |
---|---|---|---|
Next Message | Amit Langote | 2017-01-25 01:02:35 | Re: Declarative partitioning - another take |
Previous Message | Alvaro Herrera | 2017-01-25 00:32:56 | Re: patch: function xmltable |