[postgis-users] find adjacent polygons query problem

[Alex Kuznetsov]

Hello List!

If I run the query like this:

SELECT a.caname FROM ca23jan06 a, ca23jan06 b
WHERE b.caname = 'Cataraqui Region' AND a.the_geom && b.the_geom
GROUP BY a.caname ORDER BY a.caname;

it returns the result instantly,
but if I try something like this:

SELECT a.caname FROM ca23jan06 a, ca23jan06 b
WHERE b.caname = 'Cataraqui Region' AND a.the_geom && b.the_geom
AND distance(a.the_geom, b.the_geom) = 0
GROUP BY a.caname ORDER BY a.caname;

or this:

SELECT a.caname FROM ca23jan06 a, ca23jan06 b
WHERE b.caname = 'Cataraqui Region' AND a.the_geom && b.the_geom
AND touches(a.the_geom, b.the_geom)
GROUP BY a.caname ORDER BY a.caname;

the process takes forever and I have to interrupt this violently

I've built oid index for ca23jan06 but it doesn't help
What can be the cause of such a behavior?

Any idea will be much appreciated,

Thank you,

Alex Kuznetsov
SSFC GIS student
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