org.datanucleus.store.rdbms.sql.method

Class MapSizeMethod

java.lang.Object

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

All Implemented Interfaces:

SQLMethod

public class MapSizeMethod
extends Object
implements SQLMethod

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).

Constructor Summary

Constructors

Constructor and Description
MapSizeMethod()

Method Summary

Modifier and Type	Method and Description
SQLExpression	getExpression(SQLStatement stmt, SQLExpression expr, List<SQLExpression> args) Return the expression for this SQL function.

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(SQLStatement stmt,
                                   SQLExpression expr,
                                   List<SQLExpression> args)

Description copied from interface: SQLMethod

Return the expression for this SQL function.

Specified by:

getExpression in interface SQLMethod

Parameters:

stmt - SQLStatement that this expression is for

expr - The expression that it is invoked on

args - Arguments passed in

Returns:

The SQL expression using the SQL function