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WFS: Don't issue STARTINDEX if feature count is small
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Datasources with no primary key cannot be naturally ordered by the
server, and so using the STARTINDEX argument causes a 400 error with the
response:

> Cannot do natural order without a primary key, please add it or
> specify a manual sort over existing attributes

This change avoids issuing STARTINDEX if:
* the feature count is known by the time the first GetFeature request is
  issued
* the feature count is less than the page size.

In other words, this change allows us to use small datasets that have no
primary key, while still allowing paging in larger datasets (as long
as they have a primary key)
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@craigds
craigds committed Jul 27, 2023
1 parent c954900 commit aeb4a11
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Showing 2 changed files with 114 additions and 5 deletions.
101 changes: 100 additions & 1 deletion autotest/ogr/ogr_wfs.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3920,9 +3920,108 @@ def test_ogr_wfs_vsimem_wfs200_paging(with_and_without_streaming):
# return 'fail'


def test_ogr_wfs_vsimem_wfs200_with_no_primary_key(with_and_without_streaming):
# This server 'supports' paging, but the datasource doesn't have a primary key,
# so in practice doesn't actually support paging.
with gdal.config_options(
{"OGR_WFS_PAGING_ALLOWED": "ON", "OGR_WFS_PAGE_SIZE": "2"}
):
with gdaltest.tempfile(
"/vsimem/wfs200_endpoint_no_pk?SERVICE=WFS&REQUEST=GetCapabilities",
"""
<WFS_Capabilities version="2.0.0">
<OperationsMetadata>
<ows:Operation name="GetFeature">
<ows:Constraint name="CountDefault">
<ows:NoValues/>
<ows:DefaultValue>2</ows:DefaultValue>
</ows:Constraint>
</ows:Operation>
<ows:Constraint name="ImplementsResultPaging">
<ows:NoValues/><ows:DefaultValue>TRUE</ows:DefaultValue>
</ows:Constraint>
</OperationsMetadata>
<FeatureTypeList>
<FeatureType>
<Name>my_layer</Name>
<Title>title</Title>
<Abstract>abstract</Abstract>
<Keywords>
<Keyword>keyword</Keyword>
</Keywords>
<DefaultSRS>urn:ogc:def:crs:EPSG::4326</DefaultSRS>
<ows:WGS84BoundingBox>
<ows:LowerCorner>-180.0 -90.0</ows:LowerCorner>
<ows:UpperCorner>180.0 90.0</ows:UpperCorner>
</ows:WGS84BoundingBox>
</FeatureType>
</FeatureTypeList>
</WFS_Capabilities>
""",
), gdaltest.tempfile(
"/vsimem/wfs200_endpoint_no_pk?SERVICE=WFS&VERSION=2.0.0&REQUEST=DescribeFeatureType&TYPENAME=my_layer",
"""
<xsd:schema xmlns:foo="http://foo" xmlns:gml="http://www.opengis.net/gml" xmlns:xsd="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified" targetNamespace="http://foo">
<xsd:import namespace="http://www.opengis.net/gml" schemaLocation="http://foo/schemas/gml/3.2.1/base/gml.xsd"/>
<xsd:complexType name="my_layerType">
<xsd:complexContent>
<xsd:extension base="gml:AbstractFeatureType">
<xsd:sequence>
</xsd:sequence>
</xsd:extension>
</xsd:complexContent>
</xsd:complexType>
<xsd:element name="my_layer" substitutionGroup="gml:_Feature" type="foo:my_layerType"/>
</xsd:schema>
""",
), gdaltest.tempfile(
"/vsimem/wfs200_endpoint_no_pk?SERVICE=WFS&VERSION=2.0.0&REQUEST=GetFeature&TYPENAMES=my_layer&RESULTTYPE=hits",
"""
<wfs:FeatureCollection
numberMatched="2" numberReturned="0" timeStamp="2023-07-27T05:19:16.504Z"
/>
""",
), gdaltest.tempfile(
"/vsimem/wfs200_endpoint_no_pk?SERVICE=WFS&VERSION=2.0.0&REQUEST=GetFeature&TYPENAMES=my_layer&COUNT=2",
"""<wfs:FeatureCollection xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:ogc="http://www.opengis.net/ogc"
xmlns:foo="http://foo"
xmlns:wfs="http://www.opengis.net/wfs"
xmlns:ows="http://www.opengis.net/ows"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:gml="http://www.opengis.net/gml"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
numberMatched="unknown" numberReturned="2"
timeStamp="2015-04-17T14:14:24.859Z"
xsi:schemaLocation="http://foo /vsimem/wfs_endpoint?SERVICE=WFS&amp;VERSION=2.0.0&amp;REQUEST=DescribeFeatureType&amp;TYPENAME=my_layer
http://www.opengis.net/wfs/2.0 http://schemas.opengis.net/wfs/2.0/wfs.xsd">
<gml:featureMembers>
<foo:my_layer gml:id="my_layer.1">
</foo:my_layer>
</gml:featureMembers>
<gml:featureMembers>
<foo:my_layer gml:id="my_layer.2">
</foo:my_layer>
</gml:featureMembers>
</wfs:FeatureCollection>""",
):
ds = ogr.Open("WFS:/vsimem/wfs200_endpoint_no_pk")
lyr = ds.GetLayer(0)

# First, ensure the feature count is known.
# This prevents the driver from adding the STARTINDEX parameter to the GetFeature request.
assert lyr.GetFeatureCount() == 2

f = lyr.GetNextFeature()
assert f is not None
f = lyr.GetNextFeature()
assert f is not None
f = lyr.GetNextFeature()
assert f is None


###############################################################################
def test_ogr_wfs_vsimem_wfs200_json(with_and_without_streaming):

with gdaltest.tempfile(
"/vsimem/wfs200_endpoint_json?SERVICE=WFS&REQUEST=GetCapabilities",
"""<WFS_Capabilities version="2.0.0">
Expand Down
18 changes: 14 additions & 4 deletions ogr/ogrsf_frmts/wfs/ogrwfslayer.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -438,12 +438,22 @@ CPLString OGRWFSLayer::MakeGetFeatureURL(int nRequestMaxFeatures,

if (poDS->IsPagingAllowed() && !bRequestHits)
{
osURL = CPLURLAddKVP(
osURL, "STARTINDEX",
CPLSPrintf("%d", nPagingStartIndex + poDS->GetBaseStartIndex()));
nRequestMaxFeatures = poDS->GetPageSize();
/* If the feature count is known and is less than the page size, we don't
* need to do paging. Skipping the pagination parameters improves compatibility
* with remote datasources that don't have a primary key.
* Without a primary key, the WFS server can't support paging, since there
* is no natural sort order defined. */
if (nFeatures < 0 ||
(nRequestMaxFeatures && nFeatures > nRequestMaxFeatures))
{
osURL =
CPLURLAddKVP(osURL, "STARTINDEX",
CPLSPrintf("%d", nPagingStartIndex +
poDS->GetBaseStartIndex()));
bPagingActive = true;
}
nFeatureCountRequested = nRequestMaxFeatures;
bPagingActive = true;
}

if (nRequestMaxFeatures)
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