Rename attributes support for postgres provider

src/providers/postgres/qgspostgresprovider.cpp

@@ -1123,7 +1123,7 @@ bool QgsPostgresProvider::hasSufficientPermsAndCapabilities()
       testAccess = connectionRO()->PQexec( sql );
       if ( testAccess.PQresultStatus() == PGRES_TUPLES_OK && testAccess.PQntuples() == 1 )
       {
-        mEnabledCapabilities |= QgsVectorDataProvider::AddAttributes | QgsVectorDataProvider::DeleteAttributes;
+        mEnabledCapabilities |= QgsVectorDataProvider::AddAttributes | QgsVectorDataProvider::DeleteAttributes | QgsVectorDataProvider::RenameAttributes;
       }
     }
   }
@@ -2251,6 +2251,66 @@ bool QgsPostgresProvider::deleteAttributes( const QgsAttributeIds& ids )
   return returnvalue;
 }
 
+bool QgsPostgresProvider::renameAttributes( const QgsFieldNameMap& renamedAttributes )
+{
+  if ( mIsQuery )
+    return false;
+
+
+  QString sql = "BEGIN;";
+
+  QgsFieldNameMap::const_iterator renameIt = renamedAttributes.constBegin();
+  bool returnvalue = true;
+  for ( ; renameIt != renamedAttributes.constEnd(); ++renameIt )
+  {
+    int fieldIndex = renameIt.key();
+    if ( fieldIndex < 0 || fieldIndex >= mAttributeFields.count() )
+    {
+      pushError( tr( "Invalid attribute index: %1" ).arg( fieldIndex ) );
+      return false;
+    }
+    if ( mAttributeFields.indexFromName( renameIt.value() ) >= 0 )
+    {
+      //field name already in use
+      pushError( tr( "Error renaming field %1: name '%2' already exists" ).arg( fieldIndex ).arg( renameIt.value() ) );
+      return false;
+    }
+
+    sql += QString( "ALTER TABLE %1 RENAME COLUMN %2 TO %3;" )
+           .arg( mQuery,
+                 quotedIdentifier( mAttributeFields.at( fieldIndex ).name() ),
+                 quotedIdentifier( renameIt.value() ) );
+  }
+  sql += "COMMIT;";
+
+  QgsPostgresConn* conn = connectionRW();
+  if ( !conn )
+  {
+    return false;
+  }
+  conn->lock();
+
+  try
+  {
+    conn->begin();
+    //send sql statement and do error handling
+    QgsPostgresResult result( conn->PQexec( sql ) );
+    if ( result.PQresultStatus() != PGRES_COMMAND_OK )
+      throw PGException( result );
+    returnvalue = conn->commit();
+  }
+  catch ( PGException &e )
+  {
+    pushError( tr( "PostGIS error while renaming attributes: %1" ).arg( e.errorMessage() ) );
+    conn->rollback();
+    returnvalue = false;
+  }
+
+  loadFields();
+  conn->unlock();
+  return returnvalue;
+}
+
 bool QgsPostgresProvider::changeAttributeValues( const QgsChangedAttributesMap &attr_map )
 {
   bool returnvalue = true;

src/providers/postgres/qgspostgresprovider.h

@@ -196,15 +196,9 @@ class QgsPostgresProvider : public QgsVectorDataProvider
       @return true in case of success and false in case of failure*/
     bool deleteFeatures( const QgsFeatureIds & id ) override;
 
-    /** Adds new attributes
-      @param name map with attribute name as key and type as value
-      @return true in case of success and false in case of failure*/
     bool addAttributes( const QList<QgsField> &attributes ) override;
-
-    /** Deletes existing attributes
-      @param names of the attributes to delete
-      @return true in case of success and false in case of failure*/
     bool deleteAttributes( const QgsAttributeIds &name ) override;
+    virtual bool renameAttributes( const QgsFieldNameMap& renamedAttributes ) override;
 
     /** Changes attribute values of existing features
       @param attr_map a map containing the new attributes. The integer is the feature id,

tests/src/python/test_provider_postgres.py

@@ -231,6 +231,44 @@ class TestPyQgsPostgresProvider(unittest.TestCase, ProviderTestCase):
             if 'precision' in e:
                 self.assertEqual(fields.at(fields.indexFromName(f)).precision(), e['precision'])
 
+    def testRenameAttributes(self):
+        ''' Test renameAttributes() '''
+        vl = QgsVectorLayer('%s table="qgis_test"."rename_table" sql=' % (self.dbconn), "renames", "postgres")
+        provider = vl.dataProvider()
+        provider.renameAttributes({1: 'field1', 2: 'field2'})
+
+        # bad rename
+        self.assertFalse(provider.renameAttributes({-1: 'not_a_field'}))
+        self.assertFalse(provider.renameAttributes({100: 'not_a_field'}))
+        # already exists
+        self.assertFalse(provider.renameAttributes({1: 'field2'}))
+
+        # rename one field
+        self.assertTrue(provider.renameAttributes({1: 'newname'}))
+        self.assertEqual(provider.fields().at(1).name(), 'newname')
+        vl.updateFields()
+        fet = next(vl.getFeatures())
+        self.assertEqual(fet.fields()[1].name(), 'newname')
+
+        # rename two fields
+        self.assertTrue(provider.renameAttributes({1: 'newname2', 2: 'another'}))
+        self.assertEqual(provider.fields().at(1).name(), 'newname2')
+        self.assertEqual(provider.fields().at(2).name(), 'another')
+        vl.updateFields()
+        fet = next(vl.getFeatures())
+        self.assertEqual(fet.fields()[1].name(), 'newname2')
+        self.assertEqual(fet.fields()[2].name(), 'another')
+
+        # close layer and reopen, then recheck to confirm that changes were saved to db
+        del vl
+        vl = None
+        vl = QgsVectorLayer('%s table="qgis_test"."rename_table" sql=' % (self.dbconn), "renames", "postgres")
+        provider = vl.dataProvider()
+        self.assertEqual(provider.fields().at(1).name(), 'newname2')
+        self.assertEqual(provider.fields().at(2).name(), 'another')
+        fet = next(vl.getFeatures())
+        self.assertEqual(fet.fields()[1].name(), 'newname2')
+        self.assertEqual(fet.fields()[2].name(), 'another')
 
 if __name__ == '__main__':
     unittest.main()

tests/testdata/provider/testdata_pg.sql

@@ -398,3 +398,17 @@ CREATE TABLE qgis_test.domains
   fld_text_domain qgis_test.text_domain,
   fld_numeric_domain qgis_test.numeric_domain
 );
+
+
+--------------------------------------
+-- Temporary table for testing renaming fields
+--
+
+CREATE TABLE qgis_test.rename_table
+(
+  gid serial NOT NULL,
+  field1 text,
+  field2 text
+);
+
+INSERT INTO qgis_test.rename_table (field1,field2) VALUES ('a','b');