Examples of org.jpox.store.rdbms.query.UnionIteratorStatement

org.jpox.store.rdbms.query.UnionIteratorStatement
Class to generate a QueryStatement for iterating through the elements of a Set. This can be in an Extent/Query for example where the user has selected a candidate class and to include/exclude subclasses. The generated query statement typically contains UNIONs for each of the possible classes involved.
To give an example, lets assume that we have class A which is the candidate and this has a subclass B. We want to find all objects of the candidate type and optionally its subclasses and we want information about what type the object is (A or B). The query will be of the form
```
 SELECT THIS.A_ID,'org.jpox.samples.A' as JPOXMETADATA, THIS.COLUMN1, THIS.COLUMN2  FROM A THIS LEFT OUTER JOIN B SUBELEMENT0 ON SUBELEMENT0.B_ID = THIS.A_ID WHERE SUBELEMENT0.B_ID IS NULL UNION SELECT THIS.A_ID,'org.jpox.samples.B' as JPOXMETADATA, THIS.COLUMN1, THIS.COLUMN2  FROM A THIS INNER JOIN B 'ELEMENT' ON 'ELEMENT'.B_ID = THIS.A_ID 
```
Extent
Here we use the above arrangement, with the "source" being the element table and the mapping being the ID column mapping.
"JoinTable" Relationship
Here the join table is the candidate table, and the "source" would be the element table, and the mapping in the join table to join to this element table PK column.
"FK" Relationship
Here we use the same arrangement as the Extent case. The "source" is the element table, and the mapping being the ID column mapping.
Map "Key" table
Here we have the key table as the candidate, and we join to the value table. So the "source" is the value table, with the mapping being the mapping of the key column in the value table.
Primitive key/value in SCO table
This also supports retrieval of keys or values of a map that are stored as a column in a different table. TODO Add full documentation for all combinations supported. TODO Commonise the code with DiscriminatorIteratorStatement @version $Revision: 1.9 $

                {
                    // "complete-table" so ignore subclasses since each table is just that class
                    useSubclassesInStatement = false;
                }


                QueryExpression query_table = new UnionIteratorStatement(clr,
                    multipleTableCase ? cls : candidateClass, useSubclassesInStatement, storeMgr,
                    clr.classForName(tables[tableNo].getType()),
                    tables[tableNo].getIDMapping(), tables[tableNo], false, Boolean.TRUE, 
                    !completeTableInheritance, false).getQueryStatement(candidateAlias);

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        {
            for (int i=0;i<elementInfo.length;i++)
            {
                final int elementNo = i;
                Class elementCls = clr.classForName(elementType);
                QueryExpression subStmt = new UnionIteratorStatement(
                    clr, elementCls, true, this.storeMgr,
                    elementCls, elementMapping, elementInfo[elementNo].getDatastoreClass(), false, 
                    null, true, false).getQueryStatement(null);
                if (stmt == null)
                {

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        {
            for (int i=0;i<elementInfo.length;i++)
            {
                final Class elementCls = clr.classForName(this.elementInfo[i].getClassName());
                final int elementNo = i;
                QueryExpression subStmt = new UnionIteratorStatement(clr, elementCls, true, this.storeMgr,
                    elementCls, elementMapping, elementInfo[elementNo].getDatastoreClass(), false, 
                    null, true, false).getQueryStatement(null);
                if (stmt == null)
                {
                    stmt = subStmt;

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            stmt.select(valueMapping);
        }
        else
        {
            // Value = PC
            stmt = new UnionIteratorStatement(clr, clr.classForName(this.valueType), true, this.storeMgr,
                clr.classForName(valueType), valueMapping, mapTable, false, null, 
                true, false).getQueryStatement(null);
        }


        // Apply condition on join-table owner field to filter by owner

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                    iterateUsingDiscriminator = true;
                }
                else
                {
                    // The element has potential subclasses and no discrim so use UNIONs
                    elementStmt = new UnionIteratorStatement(clr, elementCls, true, this.storeMgr,
                        elementCls, elementMapping, containerTable, false, Boolean.TRUE, 
                        true, allowsNull).getQueryStatement(null);
                }
                
                if (stmt == null)

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                    iterateUsingDiscriminator = true;
                }
                else
                {
                    // The element has potential subclasses and no discrim so use UNIONs
                    elementStmt = new UnionIteratorStatement(clr, elementCls, true, this.storeMgr,
                        elementCls, elementMapping, containerTable, false, Boolean.TRUE, 
                        true, allowsNull).getQueryStatement(null);
                }
                
                if (stmt == null)

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        }
        else
        {
            // Join to key table if this is join table, or value table
            boolean sourceJoin = (mapType == MAP_TYPE_JOIN || mapType == MAP_TYPE_KEY_IN_VALUE);
            stmt = new UnionIteratorStatement(clr, elementCls, true, this.storeMgr,
                elementCls, elementMapping, containerTable, sourceJoin, null, 
                true, false).getQueryStatement(null);
        }


        // Apply condition on owner field to filter by owner

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            }
            iterateUsingDiscriminator = true;
        }
        else
        {
            stmt = new UnionIteratorStatement(clr, valueCls, true, this.storeMgr,
                valueCls, valueMapping, valueTable, false, null, true, false).getQueryStatement(null);
        }


        // Apply condition on join-table owner field to filter by owner
        ScalarExpression ownerExpr = ownerMapping.newScalarExpression(stmt, stmt.getMainTableExpression());

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        QueryExpression stmt = null;
        for (int i=0;i<elementInfo.length;i++)
        {
            final int elementNo = i;
            Class elementCls = clr.classForName(elementType);
            QueryExpression subStmt = new UnionIteratorStatement(
                clr, elementCls, true, this.storeMgr,
                elementCls, elementMapping, elementInfo[elementNo].getDatastoreClass(), false, 
                null, true, false).getQueryStatement(null);
            if (stmt == null)
            {

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            ScalarExpression targetExpr = elementMapping.newScalarExpression(stmt, teTargetElement);
            stmt.innerJoin(sourceExpr, targetExpr, teTargetElement, true);
        }
        else
        {
            stmt = new UnionIteratorStatement(clr, elementCls, true, this.storeMgr,
                elementCls, elementMapping, containerTable, false, null, 
                true, false).getQueryStatement(null);
        }


        // Apply condition on owner field to filter by owner

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org.jpox.metadata.DiscriminatorMetaData

org.jpox.store.mapped.DatastoreClass

org.jpox.store.mapped.DatastoreIdentifier

org.jpox.store.mapped.expression.LogicSetExpression

org.jpox.store.mapped.expression.MetaDataStringLiteral

org.jpox.store.mapped.expression.NullLiteral

org.jpox.store.mapped.expression.QueryExpression

org.jpox.store.mapped.expression.ScalarExpression

org.jpox.store.mapped.mapping.JavaTypeMapping

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Examples of org.jpox.store.rdbms.query.UnionIteratorStatement

Extent

"JoinTable" Relationship

"FK" Relationship

Map "Key" table

Primitive key/value in SCO table

Related Classes of org.jpox.store.rdbms.query.UnionIteratorStatement