org.apache.openjpa.jdbc.kernel
Class PagingResultObjectProvider

java.lang.Object
  org.apache.openjpa.jdbc.kernel.SelectResultObjectProvider
      org.apache.openjpa.jdbc.kernel.PagingResultObjectProvider

All Implemented Interfaces:

ResultObjectProvider, Closeable

public class PagingResultObjectProvider
extends SelectResultObjectProvider

Object provider implementation that fetches one page of results at a a time as it scrolls. If the getPagedFields(org.apache.openjpa.jdbc.sql.Select, org.apache.openjpa.jdbc.meta.ClassMapping, org.apache.openjpa.jdbc.kernel.JDBCStore, org.apache.openjpa.jdbc.kernel.JDBCFetchConfiguration, int, long) method returns a non-null bit set, this this provider is a good fit for your configuration. The method tests the following conditions:

• The eager fetch mode is parallel.
• The select's result should be treated as a large result set.
• The mapping being selected has fields that use parallel selects under the current fetch configuration.

To use this provider, select the candidate mapping with eager fetch mode set to join. This provider will take care of performing parallel mode batch selects for each page it reads.

Author:

Abe White

Field Summary

Fields inherited from class org.apache.openjpa.jdbc.kernel.SelectResultObjectProvider

_res

Constructor Summary

PagingResultObjectProvider(SelectExecutor sel, ClassMapping[] mappings, JDBCStore store, JDBCFetchConfiguration fetch, BitSet[] paged, long size)
Constructor.

PagingResultObjectProvider(SelectExecutor sel, ClassMapping mapping, JDBCStore store, JDBCFetchConfiguration fetch, BitSet paged, long size)
Constructor.

Method Summary

boolean	absolute(int pos) Move to the given 0-based position.
static BitSet	getPagedFields(Select sel, ClassMapping mapping, JDBCStore store, JDBCFetchConfiguration fetch, int eagerMode, long size) Return a bit set representing batch select fields that will be paged, or null if no fields need paging, which indicates that this provider should not be used.
int	getPageSize() Return the page size in use.
Object	getResultObject() Instantiate the current result object.
boolean	next() Advance the input to the next position.
void	open() Open the result.

Methods inherited from class org.apache.openjpa.jdbc.kernel.SelectResultObjectProvider

close, getFetchConfiguration, getResult, getSelect, getStore, handleCheckedException, reset, setSize, size, supportsRandomAccess

Methods inherited from class java.lang.Object

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

Constructor Detail

PagingResultObjectProvider

public PagingResultObjectProvider(SelectExecutor sel,
                                  ClassMapping mapping,
                                  JDBCStore store,
                                  JDBCFetchConfiguration fetch,
                                  BitSet paged,
                                  long size)

Constructor.

Parameters:

sel - the select to execute

mapping - the mapping of the result objects

store - the store manager to delegate loading to

fetch - the fetch configuration, or null for default

paged - the bit set returned from getPagedFields(org.apache.openjpa.jdbc.sql.Select, org.apache.openjpa.jdbc.meta.ClassMapping, org.apache.openjpa.jdbc.kernel.JDBCStore, org.apache.openjpa.jdbc.kernel.JDBCFetchConfiguration, int, long)

size - the known maximum size of the result, or Long.MAX_VALUE for no known limit

PagingResultObjectProvider

public PagingResultObjectProvider(SelectExecutor sel,
                                  ClassMapping[] mappings,
                                  JDBCStore store,
                                  JDBCFetchConfiguration fetch,
                                  BitSet[] paged,
                                  long size)

Constructor.

Parameters:

sel - the select to execute

mappings - the mappings for the independent classes of the result objects

store - the store manager to delegate loading to

fetch - the fetch configuration, or null for default

paged - the bit sets returned from getPagedFields(org.apache.openjpa.jdbc.sql.Select, org.apache.openjpa.jdbc.meta.ClassMapping, org.apache.openjpa.jdbc.kernel.JDBCStore, org.apache.openjpa.jdbc.kernel.JDBCFetchConfiguration, int, long) for each select in the possible union

size - the known maximum size of the result, or Long.MAX_VALUE for no known limit

Method Detail

getPagedFields

public static BitSet getPagedFields(Select sel,
                                    ClassMapping mapping,
                                    JDBCStore store,
                                    JDBCFetchConfiguration fetch,
                                    int eagerMode,
                                    long size)

Return a bit set representing batch select fields that will be paged, or null if no fields need paging, which indicates that this provider should not be used.

See Also:

PagingResultObjectProvider(org.apache.openjpa.jdbc.sql.SelectExecutor, org.apache.openjpa.jdbc.meta.ClassMapping[], org.apache.openjpa.jdbc.kernel.JDBCStore, org.apache.openjpa.jdbc.kernel.JDBCFetchConfiguration, java.util.BitSet[], long)

getPageSize

public int getPageSize()

Return the page size in use.

open

public void open()
          throws SQLException

Description copied from interface: ResultObjectProvider

Open the result. This will be called before ResultObjectProvider.next(), ResultObjectProvider.absolute(int), or ResultObjectProvider.size().

Specified by:

open in interface ResultObjectProvider

Overrides:

open in class SelectResultObjectProvider

Throws:

SQLException

next

public boolean next()
             throws SQLException

Description copied from interface: ResultObjectProvider

Advance the input to the next position. Return true if there is more data; otherwise false.

Specified by:

next in interface ResultObjectProvider

Overrides:

next in class SelectResultObjectProvider

Throws:

SQLException

absolute

public boolean absolute(int pos)
                 throws SQLException

Description copied from interface: ResultObjectProvider

Move to the given 0-based position. This method is only called for providers that support random access. Return true if there is data at this position; otherwise false. This may be invoked in place of ResultObjectProvider.next().

Specified by:

absolute in interface ResultObjectProvider

Overrides:

absolute in class SelectResultObjectProvider

Throws:

SQLException

getResultObject

public Object getResultObject()
                       throws SQLException

Description copied from interface: ResultObjectProvider

Instantiate the current result object. This method will only be called after ResultObjectProvider.next() or ResultObjectProvider.absolute(int).

Throws:

SQLException