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

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

All Implemented Interfaces:

SQLMethod

public class CollectionContainsMethod
extends AbstractSQLMethod

Method for evaluating {collExpr1}.contains({elemExpr}). Returns a BooleanExpression.

Field Summary

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

clr, exprFactory, LOCALISER, stmt

Constructor Summary

CollectionContainsMethod()

Method Summary

protected SQLExpression	containsAsInnerJoin(CollectionExpression collExpr, SQLExpression elemExpr) Method to return an expression for Collection.contains using INNER JOIN to the element.
protected SQLExpression	containsAsSubquery(CollectionExpression collExpr, SQLExpression elemExpr) Method to return an expression for Collection.contains using a subquery "EXISTS".
protected boolean	elementTypeCompatible(Class elementType, Class collectionElementType)
SQLExpression	getExpression(SQLExpression expr, List args) Return the expression for this SQL function.
protected boolean	getNeedsSubquery(SQLExpression collExpr, SQLExpression elemExpr) Convenience method to decide if we handle the contains() by using a subquery, or otherwise via an inner join.

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

CollectionContainsMethod

public CollectionContainsMethod()

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

getNeedsSubquery

protected boolean getNeedsSubquery(SQLExpression collExpr,
                                   SQLExpression elemExpr)

Convenience method to decide if we handle the contains() by using a subquery, or otherwise via an inner join. If there is an OR or a NOT in the query then uses a subquery.

Parameters:

collExpr - SQL Expression for the collection

elemExpr - SQL Expression for the element

Returns:

Whether to use a subquery

containsAsInnerJoin

protected SQLExpression containsAsInnerJoin(CollectionExpression collExpr,
                                            SQLExpression elemExpr)

Method to return an expression for Collection.contains using INNER JOIN to the element. This is only for use when there are no "!contains" and no "OR" operations. Creates SQL by adding INNER JOIN to the join table (where it exists), and also to the element table adding an AND condition on the element (with value of the elemExpr). Returns a BooleanExpression "TRUE" (since the INNER JOIN will guarantee if the element is contained of not).

Parameters:

collExpr - Collection expression

elemExpr - Expression for the element

Returns:

Contains expression

containsAsSubquery

protected SQLExpression containsAsSubquery(CollectionExpression collExpr,
                                           SQLExpression elemExpr)

Method to return an expression for Collection.contains using a subquery "EXISTS". This is for use when there are "!contains" or "OR" operations in the filter. Creates the following SQL,

• Collection of NonPC using join table

   SELECT 1 FROM JOIN_TBL A0_SUB 
   WHERE A0_SUB.JOIN_OWN_ID = A0.ID AND A0_SUB.JOIN_ELEM_ID = {elemExpr}
   

• Collection of PC using join table

   SELECT 1 FROM ELEM_TABLE A0_SUB INNER JOIN JOIN_TBL B0 ON ... 
   WHERE B0.JOIN_OWN_ID = A0.ID AND A0_SUB.ID = {elemExpr}
   

• Collection of PC using FK

   SELECT 1 FROM ELEM_TABLE A0_SUB
   WHERE A0_SUB.OWN_ID = A0.ID AND A0_SUB.ID = {elemExpr}
   

and returns a BooleanSubqueryExpression ("EXISTS (subquery)")

Parameters:

collExpr - Collection expression

elemExpr - Expression for the element

Returns:

Contains expression

elementTypeCompatible

protected boolean elementTypeCompatible(Class elementType,
                                        Class collectionElementType)