org.datanucleus.store.rdbms.sql.method

Class MapContainsEntryMethod

java.lang.Object

org.datanucleus.store.rdbms.sql.method.MapContainsEntryMethod

All Implemented Interfaces:

SQLMethod

public class MapContainsEntryMethod
extends Object
implements SQLMethod

Method for evaluating {mapExpr}.containsEntry(keyExpr, valueExpr). Returns a BooleanExpression.

Constructor Summary

Constructors

Constructor and Description
MapContainsEntryMethod()

Method Summary

Modifier and Type	Method and Description
protected SQLExpression	containsAsInnerJoin(SQLStatement stmt, MapExpression mapExpr, SQLExpression keyExpr, SQLExpression valExpr) Method to return an expression for Map.containsEntry using INNER JOIN to the element.
protected SQLExpression	containsAsSubquery(SQLStatement stmt, MapExpression mapExpr, SQLExpression keyExpr, SQLExpression valExpr) Method to return an expression for Map.containsEntry 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.

Methods inherited from class java.lang.Object

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

Constructor Detail

MapContainsEntryMethod

public MapContainsEntryMethod()

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

containsAsInnerJoin

protected SQLExpression containsAsInnerJoin(SQLStatement stmt,
                                            MapExpression mapExpr,
                                            SQLExpression keyExpr,
                                            SQLExpression valExpr)

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

Parameters:

stmt - SQLStatement

mapExpr - Map expression

keyExpr - Expression for the key

valExpr - Expression for the value

Returns:

Contains expression

containsAsSubquery

protected SQLExpression containsAsSubquery(SQLStatement stmt,
                                           MapExpression mapExpr,
                                           SQLExpression keyExpr,
                                           SQLExpression valExpr)

Method to return an expression for Map.containsEntry 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_VAL_ID = {valExpr}
   AND Ao_SUB.JOIN_KEY_ID = {keyExpr}
   

• Map with key stored in value

   SELECT 1 FROM VAL_TABLE A0_SUB
   WHERE B0.JOIN_OWN_ID = A0.ID 
   AND A0_SUB.ID = {valExpr}
   AND A0_SUB.KEY_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.VAL_ID = {valExpr}
   AND A0_SUB.ID = {keyExpr}
   

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

Parameters:

stmt - SQLStatement

mapExpr - Map expression

keyExpr - Expression for the key

valExpr - Expression for the value

Returns:

Contains expression