Re: [DEPARSE] A COLLATE clause in the URI of XMLNAMESPACES does not read back

Hi Henson,

Thanks for the patch. I read the report and the patch, and tested
v1 hands-on (the hands-on testing below was done with AI assistance;
the code reading and this review are mine).

Code reading: the URI of XMLNAMESPACES is a b_expr, so it cannot
carry a COLLATE, and get_xmltable() was the one place in that function
printing an expression without parentheses -- the ROWS expression,
the PASSING document and the column expressions are all wrapped
already. In pretty mode a CollateClause drops its own parentheses,
so the printed definition is not valid input. Parenthesizing the URI
there, in both the AS-name and the DEFAULT branch, fixes it at the
right layer, and the plain-Const exception keeps the common case free
of output churn. Parenthesizing in non-pretty mode as well gives two
pairs of parentheses there, which reads back fine and is consistent
with how other operands in this function are treated.

Reproduction on current master: with views whose namespace URI carries
a COLLATE (named namespace, DEFAULT namespace, one element of a mixed
list, and a function-call URI), pg_get_viewdef(..., true) prints the
COLLATE bare, and recreating the views from those definitions fails
with 'syntax error at or near "COLLATE"' - 6 of the 12 objects in
my test battery. The non-pretty definitions round-trip, and a full
pg_dump/restore is clean on master, matching your report that this
is a pretty-printing problem only. I also confirmed that functions
are not affected, since pg_get_functiondef prints the body non-pretty.

With v1 applied, every object round-trips from both the pretty and
the non-pretty definition, with the definitions byte-identical before
and after recreation, and a pg_dump/restore is clean. Objects created
before the patch are fixed by the patched deparser alone, as expected
for a ruleutils fix. Plain-constant URIs print exactly as before
(a literal with a cast folds to a Const and is also unchanged);
operator-expression URIs gain parentheses, as your commit message
notes, and still read back. One extra form I tried: a LATERAL view
whose namespace URI is a column reference with a COLLATE also reads
back and executes correctly with the patch.

One small coverage note: the new test covers the pretty, named-AS
form. The DEFAULT form and the non-pretty output are exercised by my
testing above but are not in the patch's tests; a DEFAULT line in the
new test would be a nice addition, but I do not consider it a blocker.

I ran installcheck-world against the patched build: core regression
239/239, core isolation 134/134, contrib 206/206 + 20/20 isolation,
test modules 71/71 + 24/24 isolation - all pass.

This looks complete and correct to me.

~ Prashant