PostGIS geometry PgDAC

Discussion of open issues, suggestions and bugs regarding PgDAC (PostgreSQL Data Access Components) for Delphi, C++Builder, Lazarus (and FPC)
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Posts: 1
Joined: Fri 13 Mar 2020 09:50

PostGIS geometry PgDAC

Post by UserJK » Fri 13 Mar 2020 11:47


I have PostgreSQL database with Postgis geometry.
How to decode postgis binary geometry to 'WKT' or any other format or get PgDAC object (ex. TPgPoint) in Delphi application (or any other)

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procedure TfmMain.Button5Click(Sender: TObject);
  fld: TField;
  pgfld: TPgGeometricField;
  pGeom: TPgGeometric;
  pPoint: TPgPoint;
  pCBlob: TCompressedBlob;
  x,y: Double;
  PgQuery1.SQL.Add('SELECT * FROM test_geom');
  fld := PgQuery1.FieldByName('geometry');
  pgfld := TPgGeometricField(fld);

  pGeom := pgfld.AsPgGeometric;
  pCBlob := TCompressedBlob(pGeom);//works, but how to decode geometry data?

  pPoint := TPgPoint(pGeom);//don't work
  x := pPoint.X;
  y := pPoint.Y;
I also have tried to use postgis function ST_AsText(geometry) in SQL

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  PgQuery1.SQL.Add('SELECT ST_AsText(geometry) FROM test_geom');
But this throws me error that function st_astext(public.geometry) doesn't exist.

When I create table using point or polygon data type I can get TPgPoint.

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CREATE TABLE test_geom_point
  geometry point,
  id integer NOT NULL

INSERT INTO test_geom_point(
            geometry, id )
    VALUES (point(2,1), 1);
Unfortunately, this isn't Postgis geometry and I can't show this data in application like QGis.
Also I can't show in my application data with Postgis geometry

How to decode Postgis geometry?

Devart Team
Posts: 65
Joined: Wed 11 Mar 2020 08:28

Re: PostGIS geometry PgDAC

Post by oleg0k » Tue 17 Mar 2020 12:40

We support only official releases of database systems, and we cannot guarantee compatibility of our products with third-party solutions.
We’ll consider adding support for PostGis in future releases.

wbr, Oleg
DAC Team

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