org.eclipse.rdf4j.federated

## Class QueryManager

- java.lang.Object
- - org.eclipse.rdf4j.federated.QueryManager

-     public class QueryManager
      extends Object

  QueryManager to manage queries. a) Management of running queries (abort, finish) b) Factory to create queries
  Author:
    Andreas Schwarte

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `QueryManager()`

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `abortQuery(QueryInfo queryInfo)`
    `void` | `addPrefixDeclaration(String prefix, String namespace)` Register a prefix declaration to be used during query evaluation.
    `protected static Set<String>` | `findQueryPrefixes(String queryString)` Find all prefixes declared in the query
    `void` | `finishQuery(QueryInfo queryInfo)`
    `BigInteger` | `getNextQueryId()` Computes the (incremental) next query identifier.
    `int` | `getNumberOfRunningQueries()`
    `protected String` | `getPrefixDeclarations()` Get the prefix declarations that have to be prepended to the query.
    `protected String` | `getPrefixDeclarationsCheck(String queryString)` Get the prefix declarations that have to be added while considering prefixes that are already declared in the query.
    `String` | `getQueryPlan(String queryString)` Retrieve the query plan for the given query string.
    `Set<QueryInfo>` | `getRunningQueries()`
    `void` | `init(FedXRepository repo, FederationContext federationContext)`
    `boolean` | `isRunning(QueryInfo queryInfo)`
    `BooleanQuery` | `prepareBooleanQuery(String queryString)` Prepare a boolean query which uses the underlying federation to evaluate the query.
    `GraphQuery` | `prepareGraphQuery(String queryString)` Prepare a tuple query which uses the underlying federation to evaluate the query.
    `Query` | `prepareQuery(String queryString)` Prepare a `Query` which uses the underlying federation to evaluate the SPARQL query.
    `TupleQuery` | `prepareTupleQuery(String queryString)` Prepare a tuple query which uses the underlying federation to evaluate the query.
    `void` | `registerQuery(QueryInfo queryInfo)` Add the query to the set of running queries, queries are identified via a unique id
    `void` | `shutdown()`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### QueryManager

          public QueryManager()

  - ### Method Detail

    - #### init

          public void init(FedXRepository repo,
                           FederationContext federationContext)

    - #### shutdown

          public void shutdown()

    - #### registerQuery

          public void registerQuery(QueryInfo queryInfo)

      Add the query to the set of running queries, queries are identified via a unique id
      Parameters:
        `queryInfo` -

    - #### getRunningQueries

          public Set<QueryInfo> getRunningQueries()

    - #### getNumberOfRunningQueries

          public int getNumberOfRunningQueries()

    - #### abortQuery

          public void abortQuery(QueryInfo queryInfo)

    - #### finishQuery

          public void finishQuery(QueryInfo queryInfo)

    - #### isRunning

          public boolean isRunning(QueryInfo queryInfo)

    - #### addPrefixDeclaration

          public void addPrefixDeclaration(String prefix,
                                           String namespace)

      Register a prefix declaration to be used during query evaluation. If a known prefix is used in a query, it is substituted in the parsing step. If namespace is null, the corresponding entry is removed.
      Parameters:
        `prefix` - a common prefix, e.g. rdf
        `namespace` - the corresponding namespace, e.g. "http://www.w3.org/1999/02/22-rdf-syntax-ns#"

    - #### prepareTupleQuery

          public TupleQuery prepareTupleQuery(String queryString)
                                       throws MalformedQueryException

      Prepare a tuple query which uses the underlying federation to evaluate the query.

      The queryString is modified to use the declared PREFIX declarations, see `FedXConfig.getPrefixDeclarations()` for details.

      Parameters:
        `queryString` -
      Returns:
        the prepared tuple query
      Throws:
        `MalformedQueryException`

    - #### prepareGraphQuery

          public GraphQuery prepareGraphQuery(String queryString)
                                       throws MalformedQueryException

      Prepare a tuple query which uses the underlying federation to evaluate the query.

      The queryString is modified to use the declared PREFIX declarations, see `FedXConfig.getPrefixDeclarations()` for details.

      Parameters:
        `queryString` -
      Returns:
        the prepared graph query
      Throws:
        `MalformedQueryException`

    - #### prepareBooleanQuery

          public BooleanQuery prepareBooleanQuery(String queryString)
                                           throws MalformedQueryException

      Prepare a boolean query which uses the underlying federation to evaluate the query.

      The queryString is modified to use the declared PREFIX declarations, see `FedXConfig.getPrefixDeclarations()` for details.

      Parameters:
        `queryString` -
      Returns:
        the prepared `BooleanQuery`
      Throws:
        `MalformedQueryException`

    - #### prepareQuery

          public Query prepareQuery(String queryString)
                             throws MalformedQueryException

      Prepare a `Query` which uses the underlying federation to evaluate the SPARQL query.

      The queryString is modified to use the declared PREFIX declarations, see `FedXConfig.getPrefixDeclarations()` for details.

      Parameters:
        `queryString` -
      Returns:
        the prepared `Query`
      Throws:
        `MalformedQueryException`

    - #### getQueryPlan

          public String getQueryPlan(String queryString)
                              throws MalformedQueryException,
                                     FedXException

      Retrieve the query plan for the given query string.
      Parameters:
        `queryString` -
      Returns:
        the query plan
      Throws:
        `MalformedQueryException`
        `FedXException`

    - #### getNextQueryId

          public BigInteger getNextQueryId()

      Computes the (incremental) next query identifier. Implementation is thread safe and synchronized.
      Returns:
        the next query identifier

    - #### getPrefixDeclarations

          protected String getPrefixDeclarations()

      Get the prefix declarations that have to be prepended to the query.
      Returns:
        the prefix declarations

    - #### getPrefixDeclarationsCheck

          protected String getPrefixDeclarationsCheck(String queryString)

      Get the prefix declarations that have to be added while considering prefixes that are already declared in the query. The issue here is that duplicate declaration causes exceptions in Sesame
      Parameters:
        `queryString` -
      Returns:
        the prefix declarations

    - #### findQueryPrefixes

          protected static Set<String> findQueryPrefixes(String queryString)

      Find all prefixes declared in the query
      Parameters:
        `queryString` -
      Returns:
        the prefixes

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