org.datanucleus.store.rdbms.sql.method
Class MapSizeMethod

java.lang.Object
  org.datanucleus.store.rdbms.sql.method.AbstractSQLMethod
      org.datanucleus.store.rdbms.sql.method.MapSizeMethod

All Implemented Interfaces:

SQLMethod

public class MapSizeMethod
extends AbstractSQLMethod

Method for evaluating {mapExpr}.size(). Returns a NumericExpression. Equates to a sub-query on the table for the map returning the COUNT(*) of the number of entries. Something like

 SELECT COUNT(*) FROM MAPTABLE A0_SUB WHERE A0_SUB.OWNER_ID_OID = A0.OWNER_ID
 

where A0 is the candidate table in the outer query, and MAPTABLE is the join table (if using join map) or the key/value table (if using FK map).

Field Summary

Fields inherited from class org.datanucleus.store.rdbms.sql.method.AbstractSQLMethod

clr, exprFactory, LOCALISER, stmt

Constructor Summary

MapSizeMethod()

Method Summary

SQLExpression

getExpression(SQLExpression expr, List args) Return the expression for this SQL function.

Methods inherited from class org.datanucleus.store.rdbms.sql.method.AbstractSQLMethod

getMappingForClass, setStatement

Methods inherited from class java.lang.Object

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

Constructor Detail

MapSizeMethod

public MapSizeMethod()

Method Detail

getExpression

public SQLExpression getExpression(SQLExpression expr,
                                   List args)

Description copied from interface: SQLMethod

Return the expression for this SQL function.

Parameters:

expr - The expression that it is invoked on

args - Arguments passed in

Returns:

The SQL expression using the SQL function