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PostgreSQL DATABASE DRIVER

Table of contents

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 %APPDATA%\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 containing 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

SEE ALSO

db.connect, db.execute

Database management in GRASS GIS
Help pages for database modules
SQL support in GRASS GIS

REFERENCES

SOURCE CODE

Available at: PostgreSQL DATABASE DRIVER source code (history)

Latest change: Wednesday Nov 27 22:53:26 2024 in commit: b90ce69e88409469369ec1edb86fde8ec822af8b

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