Geografic-Information-System/scripts/v.db.join/v.db.join.py

#!/usr/bin/env python

############################################################################
#
# MODULE:       v.db.join
# AUTHOR(S):    Markus Neteler
#               Converted to Python by Glynn Clements
# PURPOSE:      Join a table to a map table
# COPYRIGHT:    (C) 2007-2009 by Markus Neteler and the GRASS Development Team
#
#               This program is free software under the GNU General Public
#               License (>=v2). Read the file COPYING that comes with GRASS
#               for details.
#
#############################################################################

#%module
#% description: Joins a database table to a vector map table.
#% keyword: vector
#% keyword: attribute table
#% keyword: database
#%end

#%option G_OPT_V_MAP
#% description: Vector map to which to join other table
#% guidependency: layer,column
#%end

#%option G_OPT_V_FIELD
#% description: Layer where to join
#% guidependency: column
#%end

#%option G_OPT_DB_COLUMN
#% description: Identifier column (e.g.: cat) in the vector table to be used for join
#% required : yes
#%end

#%option G_OPT_DB_TABLE
#% key: other_table
#% description: Other table name
#% required: yes
#% guidependency: ocolumn,scolumns
#%end

#%option G_OPT_DB_COLUMN
#% key: other_column
#% description: Identifier column (e.g.: id) in the other table used for join
#% required: yes
#%end

#%option G_OPT_DB_COLUMN
#% key: subset_columns
#% multiple: yes
#% required: no
#% description: Subset of columns from the other table
#%end

import sys
import string
import grass.script as grass
from grass.exceptions import CalledModuleError


def main():
    map = options['map']
    layer = options['layer']
    column = options['column']
    otable = options['other_table']
    ocolumn = options['other_column']
    if options['subset_columns']:
        scolumns = options['subset_columns'].split(',')
    else:
        scolumns = None
    
    f = grass.vector_layer_db(map, layer)

    maptable = f['table']
    database = f['database']
    driver   = f['driver']

    if driver == 'dbf':
	grass.fatal(_("JOIN is not supported for tables stored in DBF format"))

    if not maptable:
	grass.fatal(_("There is no table connected to this map. Unable to join any column."))

    # check if column is in map table
    if not grass.vector_columns(map, layer).has_key(column):
	grass.fatal(_("Column <%s> not found in table <%s>") % (column, maptable))

    # describe other table
    all_cols_ot = grass.db_describe(otable, driver = driver, database = database)['cols']

    # check if ocolumn is on other table
    if ocolumn not in [ocol[0] for ocol in all_cols_ot]:
	grass.fatal(_("Column <%s> not found in table <%s>") % (ocolumn, otable))

    # determine columns subset from other table
    if not scolumns:
        # select all columns from other table
        cols_to_add = all_cols_ot
    else:
        cols_to_add = []
    	# check if scolumns exists in the other table
    	for scol in scolumns:
            found = False
            for col_ot in all_cols_ot:
                if scol == col_ot[0]:
                    found = True
                    cols_to_add.append(col_ot)
                    break
            if not found:
                grass.warning(_("Column <%s> not found in table <%s>.") % (scol, otable))
    
    all_cols_tt = grass.vector_columns(map, int(layer)).keys()

    select = "SELECT $colname FROM $otable WHERE $otable.$ocolumn=$table.$column"
    template = string.Template("UPDATE $table SET $colname=(%s);" % select)

    for col in cols_to_add:
	# skip the vector column which is used for join
	colname = col[0]
	if colname == column:
	    continue
	# Sqlite 3 does not support the precision number any more
	if len(col) > 2 and driver != "sqlite":
	    coltype = "%s(%s)" % (col[1], col[2])
	else:
	    coltype = "%s" % col[1]

	colspec = "%s %s" % (colname, coltype)

	# add only the new column to the table
	if colname not in all_cols_tt:
            try:
                grass.run_command('v.db.addcolumn', map=map,
                                  columns=colspec, layer=layer)
            except CalledModuleError:
                grass.fatal(_("Error creating column <%s>") % colname)

	stmt = template.substitute(table = maptable, column = column,
				   otable = otable, ocolumn = ocolumn,
				   colname = colname)
        grass.debug(stmt, 1)
        grass.verbose(_("Updating column <%s> of vector map <%s>...") % (colname, map))
        try:
            grass.write_command('db.execute', stdin=stmt, input='-',
                                database=database, driver=driver)
        except CalledModuleError:
            grass.fatal(_("Error filling column <%s>") % colname)

    # write cmd history
    grass.vector_history(map)

    return 0
if __name__ == "__main__":
    options, flags = grass.parser()
    sys.exit(main())