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Using Logical Operators in GeoServer Filters

In this session, we want to talk about the Using logical operators to combine multiple filters in GeoServer. If you want to access the complete tutorial, click on the link.

Introduction

Logical operators in Web Feature Service (WFS) filtering are essential for combining multiple conditions within GeoServer. These operators enable users to construct complex queries, facilitating data retrieval from the WFS service. The primary logical operators include AND, OR, and NOT.

Note. This video was recorded on GeoServer 2.22.4, which is not the most up-to-date version. Currently, versions 2.25.x and 2.26.x are supported. To ensure you have the latest release, please visit this link and avoid using older versions of GeoServer.

AND

This operator combines multiple conditions into a single filter expression. The resulting expression matches only those features that meet all of the specified criteria.

  • As an example of using this filter in WFS getFeature request, navigate to the Demos page, then select Demo requests.
  • From the Request section, select the WFS_getFeature1.0.xml request.

Use the following block codes to replace line 26:

<ogc:And>
  <PropertyIsLessThan>
    <PropertyName>LAND_KM</PropertyName>
    <Literal>100000</Literal>
  </PropertyIsLessThan>
  <PropertyIsGreaterThan>
    <PropertyName>PERSONS</PropertyName>
    <Literal>5000000</Literal>
  </PropertyIsGreaterThan>
</ogc:And>

Note. In all examples in this blog post, we utilize the topp:states layer.

In this example, we applied a filter to the layer, where the value of the LAND_KM attribute, is less than 100,000 and the PERSONS is greater than 5 million people.

The results include three states: Massachusetts, New Jersey and Indiana.

To use the CQL filtering to apply the equivalent of this example, first, preview the top:states layer in the Layer Preview section. Then, add the filter CQL_FILTER=LAND_KM<100000 And PERSONS>5000000 to the end of the URL.

The complete URL for the layer is as follows:

http://localhost:8080/geoserver/topp/wms?service=WMS&version=1.1.0&request=GetMap&layers=topp%3Astates&bbox=-124.73142200000001,24.955967,-66.969849,49.371735&width=768&height=330&srs=EPSG%3A4326&styles=&format=application/openlayers&CQL_FILTER=LAND_KM<100000 And PERSONS>5000000

OR

This operator allows you to combine multiple conditions and retrieve features that satisfy any of the specified conditions. In simpler terms, at least one condition must be true for the filter to be considered a match.

Here’s an example of how to use the “OR” operator to filter a WFS layer based on two conditions.

<ogc:Or>
  <PropertyIsLessThan>
    <PropertyName>LAND_KM</PropertyName>
    <Literal>100000</Literal>
  </PropertyIsLessThan>
  <PropertyIsGreaterThan>
    <PropertyName>PERSONS</PropertyName>
    <Literal>5000000</Literal>
  </PropertyIsGreaterThan>
</ogc:Or>

Press the Submit button.

In this example, we filtered the layer to display features that meet either of these conditions: The value of the LAND_KM attribute is less than 100,000 or the PERSONS attribute represents a population greater than 5 million people. The results include 25 states.

To apply the same example using the CQL filtering and observe the results, use the following code in the URL of the layer as mentioned above:

http://localhost:8080/geoserver/topp/wms?service=WMS&version=1.1.0&request=GetMap&layers=topp%3Astates&bbox=-124.73142200000001,24.955967,-66.969849,49.371735&width=768&height=330&srs=EPSG%3A4326&styles=&format=application/openlayers&CQL_FILTER=LAND_KM<100000 Or PERSONS>5000000

NOT

In GeoServer, the NOT operator, also known as the logical negation operator, is used to invert the meaning of a filter expression. It takes one or more filter expressions and returns features that don’t meet the specified conditions.

Here’s an example of using the “NOT” operator for filtering a WFS layer by two conditions:

<ogc:Not>
  <ogc:Or>
    <PropertyIsLessThan>
      <PropertyName>LAND_KM</PropertyName>
      <Literal>100000</Literal>
    </PropertyIsLessThan>
    <PropertyIsGreaterThan>
      <PropertyName>PERSONS</PropertyName>
      <Literal>5000000</Literal>
    </PropertyIsGreaterThan>
  </ogc:Or>
</ogc:Not>

Press the Submit button.

In this example, we filtered the layer to show features that don’t meet any of these conditions. That is, neither the value of the LAND_KM attribute is less than 100,000 nor is the value of the PERSONS parameter more than 5 million people. The results include 24 states.

To see how to use the NOT operator in CQL filtering, use the following code at the end of the URL’s layer:

http://localhost:8080/geoserver/topp/wms?service=WMS&version=1.1.0&request=GetMap&layers=topp%3Astates&bbox=-124.73142200000001,24.955967,-66.969849,49.371735&width=768&height=330&srs=EPSG%3A4326&styles=&format=application/openlayers&CQL_FILTER=NOT(LAND_KM<100000 Or PERSONS>5000000)

Combine operators

GeoServer provides the capability of combining logical operators with geometric filters, enhancing the flexibility of WFS filtering. This feature enables users to create more specific and reliable filtering criteria.

Here is an example that effectively uses both spatial and comparison filtering:

<ogc:Filter>
  <ogc:And>
    <ogc:Intersects>
      <ogc:PropertyName>the_geom</ogc:PropertyName>
      <gml:LineString xmlns:gml="http://www.opengis.net/gml" srsName="EPSG:4326">
        <gml:coordinates>-73.9,43.5 -81.1,38.6 -78.57,35.5</gml:coordinates>
      </gml:LineString>          
    </ogc:Intersects>
    <PropertyIsGreaterThanOrEqualTo>
      <PropertyName>PERSONS</PropertyName>
      <Literal>10000000</Literal>
    </PropertyIsGreaterThanOrEqualTo>
  </ogc:And>
</ogc:Filter>

In this example, we filtered out states with populations exceeding 10 million, as well as states intersected by a LineString with given coordinates.

Thus, we identified New York and Pennsylvania as the two states that satisfy these conditions.

To see how to use CQL filtering for this example, follow the instance shown on the screen:

CQL_FILTER=INTERSECTS(the_geom,LINESTRING(-73.9 43.5,-81.1 38.6,-78.57 35.5)) AND PERSONS>10000000

As a final example, we examine a comprehensive scenario that incorporates different operators. This example includes a spatial operator, such as the Within filter. Additionally, it showcases two comparison operators, namely PropertyIsLike and PropertyIsGreaterThan.

To better understand these concepts, use the following example:

<ogc:Filter>
  <ogc:And>
    <ogc:Within>
      <ogc:PropertyName>the_geom</ogc:PropertyName>
      <gml:Polygon xmlns:gml="http://www.opengis.net/gml" srsName="EPSG:4326">
        <gml:outerBoundaryIs>
          <gml:LinearRing>
            <gml:coordinates>-100,30 -100,45 -80,45 -80,30 -100,30</gml:coordinates>
          </gml:LinearRing>
        </gml:outerBoundaryIs>
      </gml:Polygon>         
    </ogc:Within>
    <ogc:Or>
      <ogc:Filter>
        <ogc:PropertyIsLike wildCard="%" singleChar="_" escape="!">
          <ogc:PropertyName>STATE_NAME</ogc:PropertyName>
          <ogc:Literal>%na%</ogc:Literal>
        </ogc:PropertyIsLike>
      </ogc:Filter>
      <PropertyIsGreaterThan>
        <PropertyName>STATE_FIPS</PropertyName>
        <Literal>30</Literal>
      </PropertyIsGreaterThan>
    </ogc:Or>
  </ogc:And>
</ogc:Filter>

In this example, we use WFS filtering to extract the States that are completely enclosed within specific coordinates. Moreover, we retrieve States whose STATENAME includes the letters “na” or whose STATEFIPS value is greater than 30.

Therefore, we have identified three states that meet the specified criteria: Tennessee, Indiana, and Ohio.

To use the CQL filtering for this example, use the following code:

CQL_FILTER=Within(the_geom,Polygon((-100 30,-100 45,-80 45,-80 30,-100 30))) AND (STATE_NAME LIKE '%na%' OR STATE_FIPS > 30)

In this session, we took a brief journey through the Combining multiple operators for WFS filtering in GeoServer. If you want to access the complete tutorial, click on the link.