grass-pg(1grass) GRASS GIS User's Manual grass-pg(1grass)
PostgreSQL DATABASE DRIVER
PostgreSQL database driver enables GRASS to store vector attributes in
PostgreSQL server.
Creating a PostgreSQL database
A new database is created with createdb, see the PostgreSQL manual for
details.
Connecting GRASS to PostgreSQL
# example for connecting to a PostgreSQL server:
db.connect driver=pg database=mydb
db.login user=myname password=secret host=myserver.osgeo.org # port=5432
db.connect -p
db.tables -p
Username and password
From the PostgresQL manual:
The file .pgpass in a user’s home directory can contain passwords to be
used if the connection requires a password (and no password has been
specified otherwise). On Microsoft Windows the file is named %APP-
DATA%\postgresql\pgpass.conf (where %APPDATA% refers to the Application
Data subdirectory in the user’s profile). Alternatively, a password
file can be specified using the connection parameter passfile or the
environment variable PGPASSFILE. This file should contain lines of the
following format:
hostname:port:database:username:password
Supported SQL commands
All SQL commands supported by PostgreSQL. It’s not possible to use
C-like escapes (with backslash like \n etc) within the SQL syntax.
Operators available in conditions
All SQL operators supported by PostgreSQL.
Adding an unique ID column
Import vector module require an unique ID column which can be generated
as follows in a PostgreSQL table:
db.execute sql="ALTER TABLE mytable ADD ID integer"
db.execute sql="CREATE SEQUENCE mytable_seq"
db.execute sql="UPDATE mytable SET ID = nextval(’mytable_seq’)"
db.execute sql="DROP SEQUENCE mytable_seq"
Attribute import into PostgreSQL
CSV import into PostgreSQL:
\h copy
COPY t1 FROM ’filename’ USING DELIMITERS ’,’;
Geometry import from PostgreSQL table into GRASS
v.in.db creates a new vector (points) map from a database table con-
taining coordinates. See here for examples.
PostGIS: PostgreSQL with vector geometry
PostGIS: adds geographic object support to PostgreSQL.
Example: Import from PostGIS
In an existing PostGIS database, create the following table:
CREATE TABLE test
(
id serial NOT NULL,
mytime timestamp DEFAULT now(),
text varchar,
wkb_geometry geometry,
CONSTRAINT test_pkey PRIMARY KEY (id)
) WITHOUT OIDS;
# insert value
INSERT INTO test (text, wkb_geometry)
VALUES (’Name’,geometryFromText(’POLYGON((600000 200000,650000
200000,650000 250000,600000 250000,600000 200000))’,-1));
# register geometry column
select AddGeometryColumn (’postgis’, ’test’, ’geometry’, -1, ’GEOMETRY’, 2);
GRASS can import this PostGIS polygon map as follows:
v.in.ogr input="PG:host=localhost dbname=postgis user=neteler" layer=test \
output=test type=boundary,centroid
v.db.select test
v.info -t test
Geometry Converters
• PostGIS with shp2pgsql:
shp2pgsql -D lakespy2 lakespy2 test > lakespy2.sql
• e00pg: E00 to PostGIS filter, see also v.in.e00.
• GDAL/OGR ogrinfo and ogr2ogr: GIS vector format converter and
library, e.g. ArcInfo or SHAPE to PostGIS.
ogr2ogr -f "PostgreSQL" shapefile ??
SEE ALSO
db.connect, db.execute
Database management in GRASS GIS
Help pages for database modules
SQL support in GRASS GIS
REFERENCES
• PostgreSQL web site
• pgAdmin graphical user interface
• GDAL/OGR PostgreSQL driver documentation
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GRASS 7.8.7 grass-pg(1grass)
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