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.

Jan

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