Fix ogrLayerName handling of PostgreSQL dataset URIs

Also document "uri" parameter semantic, and add more tests.
See for background
https://lists.osgeo.org/pipermail/qgis-developer/2016-October/045311.html
REF #15698

python/plugins/processing/tests/ToolsTest.py

@@ -70,33 +70,41 @@ def test_ogrLayerName(self):
         def linkTestfile(f, t):
             os.link(os.path.join(dataFolder, f), os.path.join(tmpdir, t))
 
+        # URI from OGR provider
         linkTestfile('geom_data.csv', 'a.csv')
         name = vector.ogrLayerName(tmpdir)
         self.assertEqual(name, 'a')
 
+        # URI from OGR provider
         linkTestfile('wkt_data.csv', 'b.csv')
         name = vector.ogrLayerName(tmpdir + '|layerid=0')
         self.assertEqual(name, 'a')
         name = vector.ogrLayerName(tmpdir + '|layerid=1')
         self.assertEqual(name, 'b')
 
+        # URI from OGR provider
         name = vector.ogrLayerName(tmpdir + '|layerid=2')
         self.assertEqual(name, 'invalid-layerid')
 
+        # URI from OGR provider
         name = vector.ogrLayerName(tmpdir + '|layername=f')
         self.assertEqual(name, 'f') # layername takes precedence
 
+        # URI from OGR provider
         name = vector.ogrLayerName(tmpdir + '|layerid=0|layername=f2')
         self.assertEqual(name, 'f2') # layername takes precedence
 
+        # URI from OGR provider
         name = vector.ogrLayerName(tmpdir + '|layername=f2|layerid=0')
         self.assertEqual(name, 'f2') # layername takes precedence
 
+        # URI from Sqlite provider
         name = vector.ogrLayerName('dbname=\'/tmp/x.sqlite\' table="t" (geometry) sql=')
         self.assertEqual(name, 't')
 
-        name = vector.ogrLayerName('dbname=\'/tmp/x.sqlite\' table="s.t" (geometry) sql=')
-        self.assertEqual(name, 's.t')
+        # URI from PostgreSQL provider
+        name = vector.ogrLayerName('port=5493 sslmode=disable key=\'edge_id\' srid=0 type=LineString table="city_data"."edge" (geom) sql=')
+        self.assertEqual(name, 'city_data.edge')
 
     def testFeatures(self):
         ProcessingConfig.initialize()

python/plugins/processing/tools/vector.py

@@ -532,16 +532,43 @@ def ogrConnectionString(uri):
     return '"' + ogrstr + '"'
 
 
+#
+# The uri parameter is an URI from any QGIS provider,
+# so could have different formats.
+# Example formats:
+#
+# -- PostgreSQL provider
+# port=5493 sslmode=disable key='edge_id' srid=0 type=LineString table="city_data"."edge" (geom) sql=
+#
+# -- Spatialite provider
+# dbname='/tmp/x.sqlite' table="t" (geometry) sql='
+#
+# -- OGR provider (single-layer directory)
+# /tmp/x.gdb
+#
+# -- OGR provider (multi-layer directory)
+# /tmp/x.gdb|layerid=1
+#
+# -- OGR provider (multi-layer directory)
+# /tmp/x.gdb|layername=thelayer
+#
 def ogrLayerName(uri):
-    if 'host' in uri:
-        regex = re.compile('table="(.+?)\.(.+?)"')
-        r = regex.search(uri)
-        return '"' + r.groups()[0] + '.' + r.groups()[1] + '"'
-    elif 'dbname' in uri:
-        regex = re.compile('table="(.+?)"')
-        r = regex.search(uri)
-        return r.groups()[0]
-    elif 'layername' in uri:
+
+    # handle URIs of database providers
+    if ' table=' in uri:
+        # Matches table="schema"."table"
+        re_table_schema = re.compile(' table="([^"]*)"\."([^"]*)"')
+        r = re_table_schema.search(uri)
+        if r:
+            return r.groups()[0] + '.' + r.groups()[1]
+        # Matches table="table"
+        re_table = re.compile(' table="([^"]*)"')
+        r = re_table.search(uri)
+        if r:
+            return r.groups()[0]
+
+    # handle URIs of OGR provider with explicit layername
+    if 'layername' in uri:
         regex = re.compile('(layername=)([^|]*)')
         r = regex.search(uri)
         return r.groups()[1]