Short circuit if query yields no results

esridump/dumper.py

@@ -157,7 +157,7 @@ def get_feature_count(self):
  response = self._request('GET', url, params=query_args, headers=headers)
  count_json = self._handle_esri_errors(response, "Could not retrieve row count")
  count = count_json.get('count')
- if not count:
+ if count is None:
  raise EsriDownloadError("Server doesn't support returnCountOnly")
  return count_json['count']
 
@@ -310,6 +310,11 @@ def __iter__(self):
  except EsriDownloadError:
  self._logger.info("Source does not support feature count")
 
+ # If there are no records matching the query, short circuit and return an empty generator.
+ if row_count == 0:
+ return
+ yield
+
  page_args = []
 
  if not self._paginate_oid and row_count is not None and (metadata.get('supportsPagination') or \

tests/download_tests.py

@@ -403,3 +403,21 @@ def test_geo_queries_when_oid_enumeration_doesnt_work(self):
  # bounding boxes.
 
  self.assertEqual(2, len(data))
+
+ def test_empty_result_set_short_circuits(self):
+ self.add_fixture_response(
+ '.*/\?f=json.*',
+ 'us-il-chicago/metadata.json',
+ method='GET',
+ )
+
+ self.add_fixture_response(
+ '.*returnCountOnly=true.*',
+ 'us-il-chicago/count-only.json',
+ method='GET',
+ )
+
+ dump = EsriDumper(self.fake_url)
+ data = list(dump)
+
+ self.assertEqual(0, len(data))

tests/fixtures/us-il-chicago/count-only.json

@@ -0,0 +1 @@
+{"count":0}

tests/fixtures/us-il-chicago/metadata.json

@@ -0,0 +1 @@
+{"currentVersion":10.81,"id":28,"name":"Census Designated Places","type":"Feature Layer","description":"Census Designated Places; ACS 2017 - January 1, 2017 vintage","geometryType":"esriGeometryPolygon","sourceSpatialReference":{"wkid":102100,"latestWkid":3857},"copyrightText":"Source: U.S. Census Bureau","parentLayer":null,"subLayers":[],"minScale":1400000,"maxScale":100.00000000673367,"drawingInfo":{"renderer":{"type":"simple","symbol":{"type":"esriSFS","style":"esriSFSSolid","color":[0,0,0,0],"outline":{"type":"esriSLS","style":"esriSLSSolid","color":[230,161,138,255],"width":0.75}},"label":"","description":""},"transparency":15,"labelingInfo":null},"defaultVisibility":false,"extent":{"xmin":-19707613.1476,"ymin":-1633572.792,"xmax":19352664.3864,"ymax":11569901.304,"spatialReference":{"wkid":102100,"latestWkid":3857}},"hasAttachments":false,"htmlPopupType":"esriServerHTMLPopupTypeNone","displayField":"BASENAME","typeIdField":null,"subtypeFieldName":null,"subtypeField":null,"defaultSubtypeCode":null,"fields":[{"name":"MTFCC","type":"esriFieldTypeString","alias":"MTFCC","length":5,"domain":null},{"name":"OID","type":"esriFieldTypeString","alias":"OID","length":22,"domain":null},{"name":"GEOID","type":"esriFieldTypeString","alias":"GEOID","length":7,"domain":null},{"name":"STATE","type":"esriFieldTypeString","alias":"STATE","length":2,"domain":null},{"name":"PLACE","type":"esriFieldTypeString","alias":"PLACE","length":5,"domain":null},{"name":"BASENAME","type":"esriFieldTypeString","alias":"BASENAME","length":100,"domain":null},{"name":"NAME","type":"esriFieldTypeString","alias":"NAME","length":100,"domain":null},{"name":"LSADC","type":"esriFieldTypeString","alias":"LSADC","length":2,"domain":null},{"name":"FUNCSTAT","type":"esriFieldTypeString","alias":"FUNCSTAT","length":1,"domain":null},{"name":"PLACECC","type":"esriFieldTypeString","alias":"PLACECC","length":2,"domain":null},{"name":"AREALAND","type":"esriFieldTypeDouble","alias":"AREALAND","domain":null},{"name":"AREAWATER","type":"esriFieldTypeDouble","alias":"AREAWATER","domain":null},{"name":"CBSAPCI","type":"esriFieldTypeString","alias":"CBSAPCI","length":1,"domain":null},{"name":"NECTAPCI","type":"esriFieldTypeString","alias":"NECTAPCI","length":1,"domain":null},{"name":"STGEOMETRY","type":"esriFieldTypeGeometry","alias":"STGEOMETRY","domain":null},{"name":"CENTLAT","type":"esriFieldTypeString","alias":"CENTLAT","length":11,"domain":null},{"name":"CENTLON","type":"esriFieldTypeString","alias":"CENTLON","length":12,"domain":null},{"name":"INTPTLAT","type":"esriFieldTypeString","alias":"INTPTLAT","length":11,"domain":null},{"name":"INTPTLON","type":"esriFieldTypeString","alias":"INTPTLON","length":12,"domain":null},{"name":"PLACENS","type":"esriFieldTypeString","alias":"PLACENS","length":8,"domain":null},{"name":"OBJECTID","type":"esriFieldTypeOID","alias":"OBJECTID","domain":null}],"geometryField":{"name":"STGEOMETRY","type":"esriFieldTypeGeometry","alias":"STGEOMETRY"},"indexes":[{"name":"PLACE_57_BASENAME","fields":"BASENAME","isAscending":true,"isUnique":false,"description":""},{"name":"PLACE_57_GEOID","fields":"GEOID","isAscending":true,"isUnique":false,"description":""},{"name":"PLACE_57_LSADC","fields":"LSADC","isAscending":true,"isUnique":false,"description":""},{"name":"PLACE_57_MTFCC","fields":"MTFCC","isAscending":true,"isUnique":false,"description":""},{"name":"PLACE_57_OID","fields":"OID","isAscending":true,"isUnique":false,"description":""},{"name":"PLACE_57_PK","fields":"STATE,PLACE","isAscending":true,"isUnique":false,"description":""},{"name":"R1728765_SDE_ROWID_UK","fields":"OBJECTID","isAscending":true,"isUnique":true,"description":""},{"name":"A124382_IX1","fields":"STGEOMETRY","isAscending":true,"isUnique":true,"description":""}],"subtypes":[],"relationships":[],"canModifyLayer":false,"canScaleSymbols":false,"hasLabels":false,"capabilities":"Map,Data,Query","maxRecordCount":100000,"supportsStatistics":true,"supportsAdvancedQueries":true,"supportedQueryFormats":"JSON, geoJSON","isDataVersioned":false,"ownershipBasedAccessControlForFeatures":{"allowOthersToQuery":true},"useStandardizedQueries":true,"advancedQueryCapabilities":{"useStandardizedQueries":true,"supportsStatistics":true,"supportsHavingClause":true,"supportsCountDistinct":true,"supportsOrderBy":true,"supportsDistinct":true,"supportsPagination":true,"supportsTrueCurve":true,"supportsReturningQueryExtent":true,"supportsQueryWithDistance":true,"supportsSqlExpression":true},"supportsDatumTransformation":true,"supportsCoordinatesQuantization":true}