ERROR: "failed to locate grouping columns"

Hi all,

I'm sending this to -hackers because i don't now if it is a bug or a
expected behavior.

I have the view bellow (if the selects bellow shows unformated in this
email, i put this in http://guedesoft.net/txt/vw_error.txt too. ):

CREATE OR REPLACE VIEW vw_my_test AS
SELECT
DISTINCT
cv.cv_cdct AS cdct, -- returns a int4
cv.cv_cdcp AS cdcp, -- returns a numeric
( SELECT cp.cp_nmfts
FROM cptv cp
WHERE cp.cp_cdcp = cv.cv_cdcp) AS nmfts, -- returns a varchar
epr.epr_nrctn AS nrctn, -- returns a numeric
cv.cv_tpvnc AS tpvnc, -- returns a int4
( SELECT rg.rg_dsc
FROM rgst rg
WHERE rg.rg_idrg = cv.cv_tpvnc) AS dsc_vnc, -- returns a varchar
cv.cv_ndcdv AS ndcdv_prnc, -- returns a varchar
( SELECT ps.ps_nm
FROM pss ps
WHERE ps.ps_nrdc = cv.cv_ndcdv) AS nmdvprnc, -- returns a varchar
cvd.cvd_nmdvsld AS ndcdv_sld, -- returns a varchar
( SELECT ps.ps_nm
FROM pss ps
WHERE ps.ps_nrdc = cvd.cvd_nmdvsld) AS nmdvsld, -- returns a varchar
cv.cv_vltt AS vltt, -- returns a numeric(18,2)
( SELECT max(oc.oc_dtagn) AS max
FROM ocr oc
WHERE oc.oc_cdct = ev.ev_cdct) AS dtagn, -- returns a date
( SELECT
CASE
WHEN abs(min(pe.pe_dtvnc) - date(now())) <= 15 THEN 1231230
WHEN abs(min(pe.pe_dtvnc) - date(now())) >= 16 AND abs(min(pe.pe_dtvnc) - date(now())) <= 30 THEN 1341231
WHEN abs(min(pe.pe_dtvnc) - date(now())) >= 31 AND abs(min(pe.pe_dtvnc) - date(now())) <= 45 THEN 2345342
WHEN abs(min(pe.pe_dtvnc) - date(now())) >= 46 AND abs(min(pe.pe_dtvnc) - date(now())) <= 60 THEN 654653
WHEN abs(min(pe.pe_dtvnc) - date(now())) >= 61 AND abs(min(pe.pe_dtvnc) - date(now())) <= 90 THEN 45254
WHEN abs(min(pe.pe_dtvnc) - date(now())) >= 91 AND abs(min(pe.pe_dtvnc) - date(now())) <= 180 THEN 13425
WHEN abs(min(pe.pe_dtvnc) - date(now())) >= 181 AND abs(min(pe.pe_dtvnc) - date(now())) <= 360 THEN 12346
ELSE 13417
END AS "case"
FROM pcep pe
WHERE pe.pe_nrcntr = ev.ev_nrcntr) AS dsatr,
cv.cv_stc AS stc,
rg.rg_cdrgs AS cdrgs,
rg.rg_dsc AS dsc_stc
FROM epvnc ev
JOIN ctvn cv ON cv.cv_cdct = ev.ev_cdct
JOIN eptm epr ON epr.epr_nrcntr = ev.ev_nrcntr
JOIN rgst rg ON cv.cv_stc = rg.rg_idrg
LEFT JOIN cvdvsld cvd ON cvd.cvd_cdct = cv.cv_cdct
;

And bellow is the select that returns: "ERROR: failed to locate grouping columns"
when no rows is returned by the View above, but it runs well when one or more
rows is returned by same view.

---
SELECT cdcp, nmfts, nrctn, tpvnc, dsc_vnc, ndcdv_prnc, nmdvpr, ndcdv_sld, max(vltt)
FROM vw_my_test_
GROUP BY cdcp, nmfts, nrctn, tpvnc, dsc_vnc, ndcdv_prnc, nmdvpr, ndcdv_sld;
---

If i group only by the *int* or *numeric* fields the error don't occurs,
it only shows if i use a varchar in group by and the view returns 0 records

If i change the view above to use JOINs then all works fine... meaning the
problem is something in SUBSELECTs and VARCHAR used in that way.

Is this a bug or a expected behavior?

best regards.
--
Dickson S. Guedes
-
mail/xmpp: guedes(at)guedesoft(dot)net - skype: guediz
http://guedesoft.net - http://planeta.postgresql.org.br