org.datanucleus.store.rdbms.sql.method

Class MapContainsKeyMethod

java.lang.Object

org.datanucleus.store.rdbms.sql.method.AbstractSQLMethod

org.datanucleus.store.rdbms.sql.method.MapContainsKeyMethod

All Implemented Interfaces:

SQLMethod

public class MapContainsKeyMethod
extends AbstractSQLMethod

Method for evaluating {mapExpr}.containsKey(keyExpr). Returns a BooleanExpression.

Field Summary

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

clr, exprFactory, stmt

Constructor Summary

Constructors

Constructor and Description
MapContainsKeyMethod()

Method Summary

Modifier and Type	Method and Description
protected SQLExpression	containsAsInnerJoin(MapExpression mapExpr, SQLExpression keyExpr) Method to return an expression for Map.containsKey using INNER JOIN to the element.
protected SQLExpression	containsAsSubquery(MapExpression mapExpr, SQLExpression keyExpr) Method to return an expression for Map.containsKey using a subquery "EXISTS".
SQLExpression	getExpression(SQLExpression expr, List<SQLExpression> args) Return the expression for this SQL function.
protected boolean	getNeedsSubquery() Convenience method to decide if we handle the contains() by using a subquery, or otherwise via an inner join.
protected boolean	keyTypeCompatible(Class keyType, Class mapKeyType)

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

MapContainsKeyMethod

public MapContainsKeyMethod()

Method Detail

getExpression

public SQLExpression getExpression(SQLExpression expr,
                                   List<SQLExpression> 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()

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.

Returns:

Whether to use a subquery

containsAsInnerJoin

protected SQLExpression containsAsInnerJoin(MapExpression mapExpr,
                                            SQLExpression keyExpr)

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

Parameters:

mapExpr - Map expression

keyExpr - Expression for the key

Returns:

Contains expression

containsAsSubquery

protected SQLExpression containsAsSubquery(MapExpression mapExpr,
                                           SQLExpression keyExpr)

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

• Map using join table

   SELECT 1 FROM JOIN_TBL A0_SUB 
   WHERE A0_SUB.JOIN_OWN_ID = A0.ID AND A0_SUB.JOIN_KEY_ID = {keyExpr}
   

• Map with key stored in value

   SELECT 1 FROM KEY_TABLE A0_SUB INNER JOIN VALUE_TBL B0 ON ... 
   WHERE B0.JOIN_OWN_ID = A0.ID AND A0_SUB.ID = {keyExpr}
   

• Map of value stored in key

   SELECT 1 FROM KEY_TABLE A0_SUB
   WHERE A0_SUB.OWN_ID = A0.ID AND A0_SUB.ID = {keyExpr}
   

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

Parameters:

mapExpr - Map expression

keyExpr - Expression for the key

Returns:

Contains expression

keyTypeCompatible

protected boolean keyTypeCompatible(Class keyType,
                                    Class mapKeyType)