Module org.apache.sis.storage
Package org.apache.sis.storage.aggregate

Class JoinFeatureSet

Object
AbstractResource
AbstractFeatureSet
JoinFeatureSet
All Implemented Interfaces:
Data­Set, Feature­Set, Resource
public class JoinFeatureSet extends AbstractFeatureSet
Features containing association to features from two different sources, joined by a SQL-like JOIN condition. Each feature in this Feature­Set contains two or three properties:
  • An optional identifier created from the identifiers of the left and right features.
  • Zero or one association to a "left" feature.
  • Zero or one association to a "right" feature.
The left and right features appear together in an Join­Feature­Set instance when a value from left­Property in the first feature is equal to a value from right­Property in the second feature.

Implementation note

If iterations in one feature set is cheaper than iterations in the other feature set, then the "costly" or larger Feature­Set should be on the left side and the "cheap" Feature­Set should be on the right side.

This implementation is read-only.

Since:
1.0

  • Field Details

    • left

      public final FeatureSet left
      The first source of features.

    • condition

      public final BinaryComparisonOperator<AbstractFeature> condition
      The join condition in the form property from left feature = property from right feature. This condition specifies also if the comparison is case sensitive and how to compare multi-values.

  • Constructor Details

    • JoinFeatureSet

      public JoinFeatureSet(Resource parent, FeatureSet left, String leftAlias, FeatureSet right, String rightAlias, JoinFeatureSet.Type joinType, BinaryComparisonOperator<AbstractFeature> condition, Map<String,?> featureInfo) throws DataStoreException
      Creates a new feature set joining the two given sets. The feature­Info map defines the name, description or other information for the Feature­Type created by this method. It can contain all the properties described in Default­Feature­Type plus the following ones:
      • "identifier­Delimiter" — string to insert between left and right identifiers in the identifiers generated by the join operation. If this property is not specified, then no identifier will be generated.
      • "identifier­Prefix" — string to insert at the beginning of join identifiers (optional).
      • "identifier­Suffix" — string to insert at the end of join identifiers (optional).
      Parameters:
      parent - the parent resource, or null if none.
      left - the first source of features. This is often (but not necessarily) the largest set.
      left­Alias - name of the associations to the left features, or null for a default name.
      right - the second source of features. Should be the set in which iterations are cheapest.
      right­Alias - name of the associations to the right features, or null for a default name.
      join­Type - whether values on both sides are required (inner join), or only one side (outer join).
      condition - join condition as property from left feature = property from right feature.
      feature­Info - information about the Feature­Type of this feature set.
      Throws:
      Data­Store­Exception - if an error occurred while creating the feature set.

  • Method Details

    • getJoinType

      public JoinFeatureSet.Type getJoinType()
      Specifies whether values on both sides are required (inner join), or only one side (outer join).
      Returns:
      whether values on both sides are required (inner join), or only one side (outer join).

    • getType

      public DefaultFeatureType getType()
      Returns a description of properties that are common to all features in this dataset. This type may contain one identifier and always contains two associations, to the left and right set of features respectively.
      Returns:
      a description of properties that are common to all features in this dataset.

    • features

      public Stream<AbstractFeature> features(boolean parallel) throws DataStoreException
      Returns a stream of all features contained in this dataset.
      Parameters:
      parallel - true for a parallel stream (if supported), or false for a sequential stream.
      Returns:
      all features contained in this dataset.
      Throws:
      Data­Store­Exception - if an error occurred while creating the stream.

    • getEnvelope

      public final Optional<Envelope> getEnvelope() throws DataStoreException
      Returns the union of the envelopes in all aggregated feature sets. This method tries to find a CRS common to all feature sets. If no common CRS can be found, then the envelope is absent.
      Specified by:
      get­Envelope in interface Data­Set
      Overrides:
      get­Envelope in class Abstract­Resource
      Returns:
      union of envelopes from all dependencies.
      Throws:
      Data­Store­Exception - if an error occurred while computing the envelope.

    • createMetadata

      protected Metadata createMetadata() throws DataStoreException
      Invoked in a synchronized block the first time that get­Metadata() is invoked. The default implementation adds the information documented in the parent class, then adds the dependencies as lineages.
      Overrides:
      create­Metadata in class Abstract­Feature­Set
      Returns:
      the newly created metadata, or null if unknown.
      Throws:
      Data­Store­Exception - if an error occurred while reading metadata from the data stores.

    • clearCache

      protected void clearCache()
      Clears any cache in this resource, forcing the data to be recomputed when needed again. This method should be invoked if the data in underlying data store changed.
      Overrides:
      clear­Cache in class Abstract­Resource