Package org.datanucleus.store.rdbms.sql.method

Class MapContainsKeyMethod

java.lang.Object

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

All Implemented Interfaces:

SQLMethod

public class MapContainsKeyMethod
extends Object
implements SQLMethod

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

Constructor Summary

Constructors

Constructor	Description
MapContainsKeyMethod()

Method Summary

Modifier and Type	Method	Description
protected SQLExpression	containsAsJoin(SQLStatement stmt, MapExpression mapExpr, SQLExpression keyExpr, SQLJoin.JoinType joinType)	Method to return an expression for Map.containsKey using INNER JOIN to the element.
protected SQLExpression	containsAsSubquery(SQLStatement stmt, MapExpression mapExpr, SQLExpression keyExpr)	Method to return an expression for Map.containsKey using a subquery "EXISTS".
SQLExpression	getExpression(SQLStatement stmt, SQLExpression expr, List<SQLExpression> args)	Return the expression for this SQL function.
protected boolean	getNeedsSubquery(SQLStatement stmt)	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 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(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

getNeedsSubquery

protected boolean getNeedsSubquery(SQLStatement stmt)

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:

stmt - SQLStatement

Returns:

Whether to use a subquery

containsAsJoin

protected SQLExpression containsAsJoin(SQLStatement stmt,
                                       MapExpression mapExpr,
                                       SQLExpression keyExpr,
                                       SQLJoin.JoinType joinType)

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:

stmt - SQLStatement

mapExpr - Map expression

keyExpr - Expression for the key

joinType - Type of join

Returns:

Contains expression

containsAsSubquery

protected SQLExpression containsAsSubquery(SQLStatement stmt,
                                           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:

stmt - SQLStatement

mapExpr - Map expression

keyExpr - Expression for the key

Returns:

Contains expression

keyTypeCompatible

protected boolean keyTypeCompatible(Class keyType,
                                    Class mapKeyType)