PostGIS - Geographic Information Systems Extensions to PostgreSQL
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VERSION: 1.0.0 (2005/01/13)
MORE INFORMATION: http://postgis.refractions.net
INTRODUCTION:
This distribution contains a module which implements GIS simple
features, ties the features to rtree indexing, and provides some
spatial functions for accessing and analyzing geographic data.
Directory structure:
./ Build scripts and install directions.
./lwgeom Library source code.
./jdbc Extensions to the PostgreSQL JDBC drivers to support
the GIS objects.
./doc Documentation on the code, objects and functions
provided.
./loader A program to convert ESRI Shape files into SQL text
suitable for uploading into a PostGIS/PostgreSQL database
and a program for converting PostGIS spatial tables into
Shape files..
./examples Small programs which demonstrate ways of accessing
GIS data.
INSTALLATION:
PostGIS is compatible with PostgreSQL 7.2 and above.
To install the module, move this directory to the "contrib" directory of your
PostgreSQL source installation. Alternately, point PGSQL_SRC at your
PostgreSQL source tree either in an environment variable or editing
Makefile.config.
You *must* have a PostgreSQL source tree, and you *must* have succesfully
built and installed it for this to work.
SEE THE NOTE ON GEOS SUPPORT BELOW FOR SPECIAL COMPILATION INSTRUCTIONS
* PROJ4 SUPPORT (Recommended):
The Proj4 reprojection library is required if you want to use the
transform() function to reproject features within the database.
http://www.remotesensing.org/proj
Install Proj4 in the default location.
Edit the postgis Makefile.config and change the USE_PROJ variable to 1
and ensure that the PROJ_DIR variable points to your Proj4
installation location (/usr/local is the default).
* SPATIAL PREDICATE / GEOS SUPPORT (Recommended):
The GEOS library provides support for exact topological tests
such as Touches(), Contains(), Disjoint() and spatial operations
such as Intersection(), Union() and Buffer().
http://geos.refractions.net
In order to use the GEOS support, you *may* need to specially compile
your version of PostgreSQL to link the C++ runtime library.
To do this, invoke the PgSQL configuration script this way:
LDFLAGS=-lstdc++ ./configure --your-options-go-here
The initial LDFLAGS variable is passed through to the Makefile and
adds the C++ library to the linking stage.
Once you have compiled PgSQL with C++ support, you can enable GEOS
support in PostGIS by setting the USE_GEOS variable in the PostGIS
Makefile.config to 1, and ensure that the GEOS_DIR variable points
to your GEOS installation location (/usr/local is the default).
To compile PostGIS, as root run:
make
make install
PostGIS now requires the PL/pgSQL procedural language in order to operate
correctly. To install PL/pgSQL use the 'createlang' program from the PostgreSQL
installation. (The PostgreSQL Programmer's Guide has details if you want
to this manually for some reason.)
As postgres run:
createlang plpgsql yourdatabase
psql -f lwpostgis.sql -d yourdatabase
Installation should now be complete.
UPGRADING:
Upgrading PostGIS can be tricky, because the underlying C libraries which
support the object types and geometries may have changed between versions.
For this purpose PostGIS provides an utility script to restore a dump
produced with the pg_dump -Fc command. It is experimental so redirecting
its output to a file will help in case of problems. The procedure is
as follow:
# Create a "custom-format" dump of the database you want
# to upgrade (let's call it "olddb")
$ pg_dump -Fc olddb olddb.dump
# Restore the dump contextually upgrading postgis into
# a new database. The new database doesn't have to exist.
# Let's call it "newdb"
$ sh utils/postgis_restore.pl lwpostgis.sql newdb olddb.dump > restore.log
# Check that all restored dump objects really had to be restored from dump
# and do not conflict with the ones defined in lwpostgis.sql
$ grep ^KEEPING restore.log | less
# If upgrading from PostgreSQL < 7.5 to >= 7.5 you might want to
# drop the attrelid, varattnum and stats columns in the geometry_columns
# table, which are no-more needed. Keeping them won't hurt.
# !!! DROPPING THEM WHEN REALLY NEEDED WILL DO HURT !!!!
$ psql newdb -c "ALTER TABLE geometry_columns DROP attrelid"
$ psql newdb -c "ALTER TABLE geometry_columns DROP varattnum"
$ psql newdb -c "ALTER TABLE geometry_columns DROP stats"
# spatial_ref_sys table is restore from the dump, to ensure your custom
# additions are kept, but the distributed one might contain modification
# so you should backup your entries, drop the table and source the new one.
# If you did make additions we assume you know how to backup them before
# upgrading the table. Replace of it with the new one is done like this:
$ psql newdb
newdb=> drop table spatial_ref_sys;
DROP
newdb=> \i spatial_ref_sys.sql
Following is the "old" procedure description. IT SHOULD BE AVOIDED if possible,
as it will leave in the database many spurious functions. It is kept in this document
as a "backup" in case postgis_restore.pl won't work for you:
pg_dump -t "*" -f dumpfile.sql yourdatabase
dropdb yourdatabase
createdb yourdatabase
createlang plpgsql yourdatabase
psql -f lwpostgis.sql -d yourdatabase
psql -f dumpfile.sql -d yourdatabase
vacuumdb -z yourdatabase
USAGE:
Try the following example SQL statements to create non-OpenGIS tables and
geometries:
CREATE TABLE geom_test ( gid int4, geom geometry,name varchar(25) );
INSERT INTO geom_test ( gid, geom, name )
VALUES ( 1, 'POLYGON((0 0 0,0 5 0,5 5 0,5 0 0,0 0 0))', '3D Square');
INSERT INTO geom_test ( gid, geom, name )
VALUES ( 2, 'LINESTRING(1 1 1,5 5 5,7 7 5)', '3D Line' );
INSERT INTO geom_test ( gid, geom, name )
VALUES ( 3, 'MULTIPOINT(3 4,8 9)', '2D Aggregate Point' );
SELECT * from geom_test WHERE geom && 'BOX3D(2 2 0,3 3 0)'::box3d;
The following SQL creates proper OpenGIS entries in the SPATIAL_REF_SYS
and GEOMETRY_COLUMNS tables, and ensures that all geometries are created
with an SRID.
INSERT INTO SPATIAL_REF_SYS
( SRID, AUTH_NAME, AUTH_SRID, SRTEXT ) VALUES
( 1, 'EPSG', 4269,
'GEOGCS["NAD83",
DATUM[
"North_American_Datum_1983",
SPHEROID[
"GRS 1980",
6378137,
298.257222101
]
],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433]]'
);
CREATE TABLE geotest (
id INT4,
name VARCHAR(32)
);
SELECT AddGeometryColumn('db','geotest','geopoint',1,'POINT',2);
INSERT INTO geotest (id, name, geopoint)
VALUES (1, 'Olympia', GeometryFromText('POINT(-122.90 46.97)',1));
INSERT INTO geotest (id, name, geopoint)
VALUES (2, 'Renton', GeometryFromText('POINT(-122.22 47.50)',1));
SELECT name,AsText(geopoint) FROM geotest;
Spatial Indexes:
PostgreSQL provides support for GiST spatial indexing. The GiST scheme offers
indexing even on large objects, using a system of "lossy" indexing where
a large object is proxied by a smaller one in the index. In the case
of the PostGIS indexing system, all objects are proxied in the index by
their bounding boxes.
You can build a GiST index with:
CREATE INDEX <indexname>
ON <tablename>
USING GIST ( <geometryfield> );
Always run the "VACUUM ANALYZE <tablename>" on your tables after
creating an index. This gathers statistics which the query planner
uses to optimize index usage.
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