[postgis-users] only insert valid/closed ring geometries

[Shad Keene]

           I started using postgis recently because of the spatial capabilities, but I'm stuck now.
I
have a list of user-entered geometries that I'm inserting into a table
via perl.  I'm using the following code to insert the geometries into
the table: (ISOL basically refers to a point geometry.)


 

if ($cwa_entries[4] eq "AREA") {

$sth
= $dbh->prepare("INSERT into cwa
values(GeomFromText('POLYGON(($cwa_entries[3]))', 4326),
'$cwa_entries[6]', '$cwa_entries[5]', nextval('cwa_id_seq'),
'$cwa_entries[0]', '$cwa_entries[1]', '$cwa_entries[4]')") or die
"could not execute: $DBI::errstr";

}

elsif ($cwa_entries[4] eq "LINE") {

$sth
= $dbh->prepare("INSERT into cwa
values(GeomFromText('LINESTRING($cwa_entries[3])', 4326),
'$cwa_entries[6]', '$cwa_entries[5]', nextval('cwa_id_seq'),
'$cwa_entries[0]', '$cwa_entries[1]', '$cwa_entries[4]')") or die
"could not execute: $DBI::errstr";

}

elsif ($cwa_entries[4] eq "ISOL") {

$sth
= $dbh->prepare("INSERT into cwa
values(GeomFromText('POINT($cwa_entries[3])', 4326), '$cwa_entries[6]',
'$cwa_entries[5]', nextval('cwa_id_seq'), '$cwa_entries[0]',
'$cwa_entries[1]', '$cwa_entries[4]')") or die "could not execute:
$DBI::errstr";

}

 

$sth->execute() or die "Could not execute: $DBI::errstr";

 

Sometimes
there are values that are entered that do not represent valid
geometries.  For instance, I might get a set of coordinates that is
designated a polygon, but the last coordinates don't equal the first
coordinates(i.e. non-closed ring).  I don't have any control over the
data that reaches me(i.e. it's already designated as AREA or LINE or
ISOLD(for point).  So how can I skip the non-closed-ring geometries and only enter the valid geometries so that my script doesn't quit on me and produce an error before it enters all the data. 
Right now, I get an error on the execute statement, and it pretty much
prevents the rest of the data from being inserted into the database. 
This may be a more perl-centered question, but I thought there might be
a postgresql command that has the effect of "insert only if GeomFromText()...is valid", else move on to the next insert.  I did see the ST_IsClosed(geometry) and the ST_IsValid(geometry) statements, but I don't know how to implement them prior to the insert.  Thanks for any help.

Shad



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