Re: [HACKERS] Misleading Error Message

> >
> > > Hi all. Was working tonight and ran into the following error. Doing a
> > > union between two selects (to get around the lack of outer joins - hint
> > > hint), I was getting the error:
> > >
> > > ERROR: Each UNION clause must have the same number of columns
> > >
> > > Upon examining the SQL statement in question, I verified that it did,
> > > indeed, have the same number of columns. After some fiddling, I found the
> > > actual problem was that I was doing an ORDER BY on a column which was not
> > > being included in the two select statements. Unfortunately, the error
> > > message wasn't pointing at that.
> > >
> > > I'm not sure if this is just a simple change or implies other problems
> > > with the parser but I thought I'd toss it out onto the pile.
> >
> > Tom Lane discovered it a few days ago in relation to INSERT INTO table
> > SELECT * FROM TABLE ORDER BY col1, and col1 was not in the select target
> > list. It shows an error. We are looking at solutions.
>
> This might also interfere with latest changes I did in the
> rewrite system. Parser and rewriter now add junk attributes
> to the targetlist. I think the problem is that the union
> code (where the check is done) doesn't recognize that the
> unequal length of the targetlists is due to junk attributes.

I have added code to the parser and rewrite checks to skip counting of
resjunk nodes in checking for UNION length equality. This should fix
the problem.

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Bruce Momjian | http://www.op.net/~candle
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