Re: Review: UNNEST (and other functions) WITH ORDINALITY

On Thu, Jul 25, 2013 at 10:33:54AM -0700, David Fetter wrote:
> On Wed, Jul 24, 2013 at 09:38:15PM +0000, Andrew Gierth wrote:
> > Tom Lane said:
> > > If we did it with a WithOrdinality expression node, the result would
> > > always be of type RECORD, and we'd have to use blessed tuple
> > > descriptors to keep track of exactly which record type a particular
> > > instance emits. This is certainly do-able (see RowExpr for
> > > precedent).
> >
> > Maybe RowExpr is a precedent for something, but it has this
> > long-standing problem that makes it very hard to use usefully:
> >
> > postgres=# select (r).* from (select row(a,b) as r from (values (1,2)) v(a,b)) s;
> > ERROR: record type has not been registered
> >
> > > It seems way too short on comments. [...]
> >
> > This can certainly be addressed.
> >
> > > but it sure looks like it flat out removed several existing
> > > regression-test cases
> >
> > Here's why, in rangefuncs.sql:
> >
> > --invokes ExecReScanFunctionScan
> > SELECT * FROM foorescan f WHERE f.fooid IN (SELECT fooid FROM foorescan(5002,5004)) ORDER BY 1,2;
> >
> > I don't think that has invoked ExecReScanFunctionScan since 7.4 or so.
> > It certainly does not do so now (confirmed by gdb as well as by the
> > query plan). By all means keep the old tests if you want a
> > never-remove-tests-for-any-reason policy, but having added tests that
> > actually _do_ invoke ExecReScanFunctionScan, I figured the old ones
> > were redundant. (Also, these kinds of tests can be done a bit better
> > now with values and lateral rather than creating and dropping tables
> > just for the one test.)
> >
> > > and a few existing comments as well.
> >
> > I've double-checked, and I don't see any existing comments removed.
> >
> > > FWIW, I concur with the gripe I remember seeing upthread that the
> > > default name of the added column ought not be "?column?".
> >
> > This seems to be a common complaint, but gives rise to two questions:
> >
> > 1) what should the name be?
> >
> > 2) should users be depending on it?
> >
> > I've yet to find another db that actually documents a specific column
> > name for the ordinality column; it's always taken for granted that the
> > user should always be supplying an alias. (Admittedly there are not
> > many dbs that support it at all; DB2 does, and I believe Teradata.)
>
> Next patch: changes by Andrew Gierth, testing vs up-to-date git master
> by Yours Truly.

Greg,

Are you still on this? Do you have questions or concerns?

Cheers,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
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