Package org.apache.sis.storage
Class Query
- Object
-
- Query
-
public abstract class Query extends Object
Definition of filtering to apply for fetching a resource subset. Filtering can happen in two domains:- By filtering the
Feature
instances. - By filtering the properties in each feature instance.
Predicate<Feature>
while the second domain is equivalent to usingUnaryOperator<Feature>
.Note: it is technically possible to useCompared to the SQL language,Query
for performing more generic feature transformations, for example inserting new properties computed from other properties, but suchQuery
usages should be rare since transformations (or more generic processing) are the topic of another package. Queries are rather descriptive objects used byFeatureSet
to optimize search operations as much as possible on the resource, using for example caches and indexes.Query
contains the information in theSELECT
andWHERE
clauses of a SQL statement. AQuery
typically contains filtering capabilities and (sometime) simple attribute transformations. Well known query languages include SQL and CQL.- Since:
- 0.8
- See Also:
FeatureSet.subset(Query)
Defined in the
sis-storage
module - By filtering the