org.datanucleus.store.rdbms.query

Class BulkFetchExistsHelper

java.lang.Object

org.datanucleus.store.rdbms.query.BulkFetchExistsHelper

public class BulkFetchExistsHelper
extends Object

Helper class to generate the necessary statement for multi-valued field bulk-fetch. In simple terms if we have a query with resultant SQL like

SELECT COL1, COL2, COL3, ... FROM CANDIDATE_TBL T1 WHERE T1.COL2 = value

then to retrieve a multi-valued collection field of the candidate class it generates an SQL like

SELECT ELEM.COL1, ELEM.COL2, ... FROM ELEMENT_TBL ELEM WHERE EXISTS (
 SELECT T1.ID FROM CANDIDATE_TBL T1 WHERE T1.COL2 = value AND ELEM.OWNER_ID = T1.ID)

Obviously there are differences when using a join-table, or when the elements are embedded into the join-table, but the basic idea is we generate an iterator statement for the elements (just like the backing store normally would) except instead of restricting the statement to just a particular owner, it adds an EXISTS clause with the query as the exists subquery).

Constructor Summary

Constructors

Constructor and Description
BulkFetchExistsHelper(org.datanucleus.store.query.Query q)

Method Summary

Modifier and Type	Method and Description
void	applyParametersToStatement(PreparedStatement ps, RDBMSQueryCompilation datastoreCompilation, SQLStatement sqlStmt, Map parameters) Convenience method to apply the passed parameters to the provided bulk-fetch statement.
IteratorStatement	getSQLStatementForContainerField(org.datanucleus.metadata.AbstractClassMetaData candidateCmd, Map parameters, org.datanucleus.metadata.AbstractMemberMetaData mmd, RDBMSQueryCompilation datastoreCompilation, Set<String> mapperOptions) Convenience method to generate a bulk-fetch statement for the specified multi-valued field of the owning query.

Methods inherited from class java.lang.Object

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

Constructor Detail

BulkFetchExistsHelper

public BulkFetchExistsHelper(org.datanucleus.store.query.Query q)

Method Detail

getSQLStatementForContainerField

public IteratorStatement getSQLStatementForContainerField(org.datanucleus.metadata.AbstractClassMetaData candidateCmd,
                                                          Map parameters,
                                                          org.datanucleus.metadata.AbstractMemberMetaData mmd,
                                                          RDBMSQueryCompilation datastoreCompilation,
                                                          Set<String> mapperOptions)

Convenience method to generate a bulk-fetch statement for the specified multi-valued field of the owning query.

Parameters:

candidateCmd - Metadata for the candidate

parameters - Parameters for the query

mmd - Metadata for the multi-valued field

datastoreCompilation - The datastore compilation of the query

mapperOptions - Any options for the query to SQL mapper

Returns:

The bulk-fetch statement for retrieving this multi-valued field.

applyParametersToStatement

public void applyParametersToStatement(PreparedStatement ps,
                                       RDBMSQueryCompilation datastoreCompilation,
                                       SQLStatement sqlStmt,
                                       Map parameters)

Convenience method to apply the passed parameters to the provided bulk-fetch statement. Takes care of applying parameters across any UNIONs of elements.

Parameters:

ps - PreparedStatement

datastoreCompilation - The datastore compilation for the query itself

sqlStmt - The bulk-fetch iterator statement

parameters - The map of parameters passed in to the query