[#1879] Set DataStore to legacy mode when using PostgreSQL < 9.x

Up until now the user had to actively set legacy mode when running PG
8.x, and if not you could end up with the full datastore running on an
old postgres version. Features like the SQL search are not properly
supported on these versions, so we need to explicitly disable them when
running on PG 8.x, by setting `legacy_mode` to True.

The current behaviour is that legacy mode will be activated if
`ckan.datastore.read_url` is not present in the configuration and/or
postgres < 9.x.

ckanext/datastore/plugin.py

@@ -23,6 +23,22 @@
 ValidationError = p.toolkit.ValidationError
 
 
+def _is_legacy_mode(config):
+    '''
+        Decides if the DataStore should run on legacy mode
+
+        Returns True if `ckan.datastore.read_url` is not set in the provided
+        config object or CKAN is running on Postgres < 9.x
+    '''
+    write_url = config.get('ckan.datastore.write_url')
+
+    engine = db._get_engine({'connection_url': write_url})
+    connection = engine.connect()
+
+    return (not config.get('ckan.datastore.read_url') or
+            not db._pg_version_is_at_least(connection, '9.0'))
+
+
 class DatastoreException(Exception):
     pass
 
@@ -62,7 +78,7 @@ def configure(self, config):
         # Legacy mode means that we have no read url. Consequently sql search is not
         # available and permissions do not have to be changed. In legacy mode, the
         # datastore runs on PG prior to 9.0 (for example 8.4).
-        self.legacy_mode = 'ckan.datastore.read_url' not in self.config
+        self.legacy_mode = _is_legacy_mode(self.config)
 
         datapusher_formats = config.get('datapusher.formats', '').split()
         self.datapusher_formats = datapusher_formats or DEFAULT_FORMATS

ckanext/datastore/tests/test_unit.py

@@ -1,9 +1,11 @@
 import unittest
 import pylons
 import nose
+import mock
 
 import ckan.tests as tests
 import ckanext.datastore.db as db
+import ckanext.datastore.plugin as plugin
 
 
 class TestTypeGetters(unittest.TestCase):
@@ -35,3 +37,57 @@ def test_pg_version_check(self):
         connection = engine.connect()
         assert db._pg_version_is_at_least(connection, '8.0')
         assert not db._pg_version_is_at_least(connection, '10.0')
+
+    @mock.patch('ckanext.datastore.db._pg_version_is_at_least')
+    def test_legacy_mode_set_if_no_read_url_and_pg_9(self, pgv):
+
+        pgv.return_value = True
+
+        from pylons import config
+
+        test_config = {
+            'ckan.datastore.write_url': config['ckan.datastore.write_url'],
+        }
+
+        assert plugin._is_legacy_mode(test_config)
+
+    @mock.patch('ckanext.datastore.db._pg_version_is_at_least')
+    def test_legacy_mode_set_if_no_read_url_and_pg_8(self, pgv):
+
+        pgv.return_value = False
+
+        from pylons import config
+
+        test_config = {
+            'ckan.datastore.write_url': config['ckan.datastore.write_url'],
+        }
+
+        assert plugin._is_legacy_mode(test_config)
+
+    @mock.patch('ckanext.datastore.db._pg_version_is_at_least')
+    def test_legacy_mode_set_if_read_url_and_pg_8(self, pgv):
+
+        pgv.return_value = False
+
+        from pylons import config
+
+        test_config = {
+            'ckan.datastore.write_url': config['ckan.datastore.write_url'],
+            'ckan.datastore.read_url': config['ckan.datastore.read_url'],
+        }
+
+        assert plugin._is_legacy_mode(test_config)
+
+    @mock.patch('ckanext.datastore.db._pg_version_is_at_least')
+    def test_legacy_mode_not_set_if_read_url_and_pg_9(self, pgv):
+
+        pgv.return_value = True
+
+        from pylons import config
+
+        test_config = {
+            'ckan.datastore.write_url': config['ckan.datastore.write_url'],
+            'ckan.datastore.read_url': config['ckan.datastore.read_url'],
+        }
+
+        assert not plugin._is_legacy_mode(test_config)