/*! \page vlibPg GRASS-PostGIS data provider

by GRASS Development Team (https://grass.osgeo.org)

\tableofcontents

\section vlibPgInro Introduction

<b>GRASS-PostGIS data provider</b> allows GRASS vector library to read and
write PostGIS data directly without any external library (like in the
case of \ref vlibOgr). GRASS-PostGIS data provider is implemented
using <a
href="http://www.postgresql.org/docs/9.2/static/libpq.html">libpq
library</a>.

Note that GRASS-PostGIS data provider is compiled only when GRASS is
configured with <tt>--with-postgres</tt> switch.

See the <a
href="http://trac.osgeo.org/grass/wiki/Grass7/VectorLib/PostGISInterface">trac
page</a> for more info.

\section vlibFn List of functions

Note that the functions listed below are lower level subroutines, in
other word these functions are not considered to be part of public
API. They are internally used by the vector library when accessing
PostGIS data. The programmer should use higher level functions
instead.

- Vect_open_old() to open existing vector map (ie. PostGIS table when using GRASS-PostGIS data provider)
- Vect_open_new() to create new vector map
- Vect_close() to close vector map

- Vect_rewind() to rewind the map for sequential access
- Vect_read_next_line() for sequential access
- Vect_read_line() for random access

- Vect_write_line() to write a new feature
- Vect_delete_line() to delete existing feature
- Vect_rewrite_line() to modify existing feature

- Vect_build() to build (pseudo-)topology

Note that functions with <tt>V1_</tt> prefix access vector data
without topology. Topological (pseudo-topological for simple features)
access is provided by functions starting with <tt>V2_</tt> prefix.

\par Open/Create PostGIS table as GRASS vector map

- V1_open_old_pg()
- V2_open_old_pg()

- V1_open_new_pg()

- V1_close_pg()
- V2_close_pg()

\par Read access

- V1_rewind_pg()
- V2_rewind_pg()

- V1_read_next_line_pg()
- V2_read_next_line_pg()

- V1_read_line_pg()
- V2_read_line_sfa()
- V2_read_line_pg()

\par Write new feature or topological element

- V1_write_line_pg()
- V2_write_line_sfa() - write new simple feature
- V2_write_line_pg() - write new topological element in PostGIS Topology schema

\par Delete existing feature or topological element

- V1_delete_line_pg()
- V2_delete_line_sfa() - delete simple feature
- V2_delete_line_pg() - delete topological element from PostGIS Topology schema

\par Modify existing feature or topological element

- V1_rewrite_line_pg()
- V2_rewrite_line_sfa() - modify simple feature
- V2_rewrite_line_pg() - modify topological element from PostGIS Topology schema

\par Build topology

- Vect_open_topo_pg()
- Vect__build_sfa()
- Vect_build_pg()
 
\section vlibPgSeeAlso See Also

 - \ref vlibOgr

\section vlibPgAuthors Authors

Martin Landa <landa.martin gmail.com>

*/