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Source code for script.db

"""
Database related functions to be used in Python scripts.

Usage:

::

    from grass.script import db as grass

    grass.db_describe(table)
    ...

(C) 2008-2015 by 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.

.. sectionauthor:: Glynn Clements
.. sectionauthor:: Martin Landa <landa.martin gmail.com>
"""
from __future__ import absolute_import
from .core import *
from .utils import try_remove
from grass.exceptions import CalledModuleError


[docs]def db_describe(table, **args): """Return the list of columns for a database table (interface to `db.describe -c`). Example: >>> run_command('g.copy', vector='firestations,myfirestations') 0 >>> db_describe('myfirestations') # doctest: +ELLIPSIS {'nrows': 71, 'cols': [['cat', 'INTEGER', '20'], ... 'ncols': 22} >>> run_command('g.remove', flags='f', type='vector', name='myfirestations') 0 :param str table: table name :param list args: :return: parsed module output """ s = read_command('db.describe', flags='c', table=table, **args) if not s: fatal(_("Unable to describe table <%s>") % table) cols = [] result = {} for l in s.splitlines(): f = l.split(':') key = f[0] f[1] = f[1].lstrip(' ') if key.startswith('Column '): n = int(key.split(' ')[1]) cols.insert(n, f[1:]) elif key in ['ncols', 'nrows']: result[key] = int(f[1]) else: result[key] = f[1:] result['cols'] = cols return result
[docs]def db_table_exist(table, **args): """Check if table exists. If no driver or database are given, then default settings is used (check db_connection()). >>> run_command('g.copy', vector='firestations,myfirestations') 0 >>> db_table_exist('myfirestations') True >>> run_command('g.remove', flags='f', type='vector', name='myfirestations') 0 :param str table: table name :param args: :return: True for success, False otherwise """ nuldev = file(os.devnull, 'w+') ok = True try: run_command('db.describe', flags='c', table=table, stdout=nuldev, stderr=nuldev, **args) except CalledModuleError: ok = False finally: nuldev.close() return ok
[docs]def db_connection(force=False): """Return the current database connection parameters (interface to `db.connect -g`). Example: >>> db_connection() {'group': '', 'schema': '', 'driver': 'sqlite', 'database': '$GISDBASE/$LOCATION_NAME/$MAPSET/sqlite/sqlite.db'} :param force True to set up default DB connection if not defined :return: parsed output of db.connect """ try: nuldev = file(os.devnull, 'w') conn = parse_command('db.connect', flags='g', stderr=nuldev) nuldev.close() except CalledModuleError: conn = None if not conn and force: run_command('db.connect', flags='c') conn = parse_command('db.connect', flags='g') return conn
[docs]def db_select(sql=None, filename=None, table=None, **args): """Perform SQL select statement Note: one of <em>sql</em>, <em>filename</em>, or <em>table</em> arguments must be provided. Examples: >>> run_command('g.copy', vector='firestations,myfirestations') 0 >>> db_select(sql = 'SELECT cat,CITY FROM myfirestations WHERE cat < 4') (('1', 'Morrisville'), ('2', 'Morrisville'), ('3', 'Apex')) Simplyfied usage (it performs <tt>SELECT * FROM myfirestations</tt>.) >>> db_select(table = 'myfirestations') # doctest: +ELLIPSIS (('1', '24', 'Morrisville #3', ... 'HS2A', '1.37')) >>> run_command('g.remove', flags='f', type='vector', name='myfirestations') 0 :param str sql: SQL statement to perform (or None) :param str filename: name of file with SQL statements (or None) :param str table: name of table to query (or None) :param str args: see \gmod{db.select} arguments """ fname = tempfile(create=False) if sql: args['sql'] = sql elif filename: args['input'] = filename elif table: args['table'] = table else: fatal(_("Programmer error: '%(sql)s', '%(filename)s', or '%(table)s' must be provided") % {'sql': 'sql', 'filename': 'filename', 'table': 'table'} ) if 'sep' not in args: args['sep'] = '|' try: run_command('db.select', quiet=True, flags='c', output=fname, **args) except CalledModuleError: fatal(_("Fetching data failed")) ofile = open(fname) result = [tuple(x.rstrip(os.linesep).split(args['sep'])) for x in ofile.readlines()] ofile.close() try_remove(fname) return tuple(result)
[docs]def db_table_in_vector(table): """Return the name of vector connected to the table. It returns None if no vectors are connected to the table. >>> run_command('g.copy', vector='firestations,myfirestations') 0 >>> db_table_in_vector('myfirestations') ['myfirestations@user1'] >>> db_table_in_vector('mfirestations') >>> run_command('g.remove', flags='f', type='vector', name='myfirestations') 0 :param str table: name of table to query """ from .vector import vector_db nuldev = file(os.devnull, 'w') used = [] vects = list_strings('vect') for vect in vects: for f in vector_db(vect, stderr=nuldev).values(): if not f: continue if f['table'] == table: used.append(vect) break if len(used) > 0: return used else: return None
[docs]def db_begin_transaction(driver): """Begin transaction. :return: SQL command as string """ if driver in ('sqlite', 'pg'): return 'BEGIN' if driver == 'mysql': return 'START TRANSACTION' return ''
[docs]def db_commit_transaction(driver): """Commit transaction. :return: SQL command as string """ if driver in ('sqlite', 'pg', 'mysql'): return 'COMMIT' return ''

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