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76 lines
2.5 KiB
Python
76 lines
2.5 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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ogrds.py
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---------------------
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Date : November 2012
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Copyright : (C) 2012 by Victor Olaya
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Email : volayaf at gmail dot com
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***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************
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"""
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__author__ = 'Victor Olaya'
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__date__ = 'November 2012'
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__copyright__ = '(C) 2012, Victor Olaya'
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# This will get replaced with a git SHA1 when you do a git archive
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__revision__ = '$Format:%H$'
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from osgeo import ogr
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class OgrDs:
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def __init__(self, format, ds):
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self.open(format, ds)
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def open(self, format, ds):
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driver = ogr.GetDriverByName(format)
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self.ds = driver.CreateDataSource(ds)
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return self.ds
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def close(self):
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if self.ds is not None:
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self.ds.Destroy()
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def execute_sql(self, sql_statement):
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poResultSet = self.ds.ExecuteSQL(sql_statement, None, None)
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if poResultSet is not None:
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self.ds.ReleaseResultSet(poResultSet)
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def select_values(self, sql_statement):
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"""Returns an array of the values of the first column in a select:
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select_values(ds, "SELECT id FROM companies LIMIT 3") => [1,2,3]
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"""
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values = []
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poResultSet = self.ds.ExecuteSQL(sql_statement, None, None)
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if poResultSet is not None:
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poDefn = poResultSet.GetLayerDefn()
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poFeature = poResultSet.GetNextFeature()
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while poFeature is not None:
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for iField in range(poDefn.GetFieldCount()):
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values.append(poFeature.GetFieldAsString(iField))
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poFeature = poResultSet.GetNextFeature()
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self.ds.ReleaseResultSet(poResultSet)
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return values
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def table_exists(self, table):
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exists = True
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try:
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self.ds.ExecuteSQL('SELECT 1 FROM %s' % table, None, None)
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except:
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exists = False
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return exists
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