Querying PostGIS point layer

[DjwStone]

Some time ago, I had trouble using CGI to query a PostGIS point layer defined
by:

    DATA          "geom FROM (select <listoffields> from testloc where
(<criteria>) AS foo USING UNIQUE <keyfield> USING srid=27700"

In browse mode, this layer displayed OK as symbols on the map, but changing
the [mode] to 'query', and clicking a point should have invoked a simple
template showing <listoffields> formatted with boilerplate text. But what
actually appeared was a completely blank page.

The workaround (thanks to Perry Nacionales) was simply to leave out the
'USING UNIQUE <keyfield>', and sure enough this remedies the problem.

However, everything I've read suggests that the USING UNIQUE... is de
rigueur for querying. Does leaving it out imply a performance hit? (OK,
working slowly is better than not working at all) Or is there some other
wrinkle I've overlooked that's needed to make the thing work with USING
UNIQUE?

Dave

Footnote:
'testloc' in the DATA statement above is a 5-table join view.
I've tried specifying the <keyfield> as both a base column-name and an alias
without success.

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