= PostGIS FAQ =

Frequently Asked Questions about PostGIS extension.

[[TOC(depth=2, noheading, inline)]]

== PostgreSQL Can't install under Windows Vista ==
Refer to these instructions [UsersWikiWinVista Issues with installing under Windows Vista]

== How to create geometry from hex-encoded Well-Known-Binary string using SQL? ==

This is two-steps operation which can be executed in single [http://www.postgresql.org/docs/8.3/static/sql-commands.html SQL] statement. The steps include:
 * Convert [http://postgis.refractions.net/documentation/manual-svn/ch04.html Well-Known-Binary] data in hexadecimal string form to raw binary using PostgreSQL function [http://www.postgresql.org/docs/8.3/static/functions-binarystring.html decode].
 * Construct geometry object from WKB in raw binary form.

Example:

{{{
#!sql
=# SELECT ST_AsText(ST_GeomFromWKB(decode('0101000000e5d022dbf93e2e40dbf97e6abc743540', 'hex'), -1));
      st_astext       
----------------------
 POINT(15.123 21.456)
}}}

== How to write geometry Well-Known-Binary to hex-encoded string? ==

First, query for geometry object in [http://postgis.refractions.net/documentation/manual-svn/ch04.html Well-Known-Binary] format using [http://postgis.refractions.net/documentation/manual-svn/ST_AsBinary.html ST_AsBinary] function. Then, [http://www.postgresql.org/docs/8.3/static/functions-binarystring.html encode] raw WKB to hex string.

Examples:

 * selecting geometry from table:

{{{
#!sql
# SELECT encode(ST_AsBinary(the_geom), 'hex');
                   encode                   
--------------------------------------------
 0101000000e5d022dbf93e2e40dbf97e6abc743540
}}}

 * constructing geometry in-place from given Well-Known-Text:

{{{
#!sql
# SELECT encode(ST_AsBinary(ST_GeomFromText('POINT(15.123 21.456)', -1)), 'hex');
                   encode                   
--------------------------------------------
 0101000000e5d022dbf93e2e40dbf97e6abc743540
}}}

== When were the ST_* functions first added to match the SQL-MM-centric convention? ==

As of PostGIS 1.3 the renaming has been in effect, as the '''1.3 tag''' is the first appearance of ST_ prefixed functions in source:tags/1.3.0/lwgeom/lwpostgis.sql.in 

Therefore, non-prefixed functions (with ST_* equivalents) are '''deprecated''', and since the 1.3 release may not be maintained in the same way as the official ST_* functions, so '''don't expect them to work the same'''.

For example only `ST_AsBinary` has been upgraded to work with the new `geography` type because `AsBinary` should not be being used anymore.

Application developers should consider upgrading their code to use ST_* functions as soon as possible, therefore requiring at least PostGIS >=1.3. 

As Background: The official PostGIS documentation [http://postgis.refractions.net/docs/reference.html | states that] most functions have been renamed and "The non ST_ functions not listed in this documentation are deprecated and will be removed in a future release so STOP USING THEM."