Examples of org.apache.derby.vti.DeferModification

org.apache.derby.vti.DeferModification
This interface is implemented by a read/write VTI class that wants to control when modifications to the VTI are deferred, or to be notified that a it is to be modified. Consider the following statement:
UPDATE NEW myVTI(...) SET cost = cost + 10 WHERE cost < 15
Updating a column that is used in the WHERE clause might or might not give the VTI implementation trouble; the update might cause the same row to be selected more than once. This problem can be solved by building the complete list of rows to be updated and the new column values before updating any rows. The updates are applied after the list is built. This process is called "deferred update".
By default, updates on a VTI are deferred when the VTI ResultSet is scrollable (ResultSet.TYPE_SCROLL_SENSITIVE or TYPE_SCROLL_INSENSITIVE), and one or more of the following is true.
1. One or more of the columns in the SET clause is also used in the WHERE clause and the VTI ResultSet is sensitive. We do not defer updates when the ResultSet is TYPE_SCROLL_INSENSITIVE because it is not necessary.
2. The where clause contains a subselect on a VTI from the same class as the target VTI. We do not look at the VTI parameters, just the VTI class name.
By default, deletes on a VTI are deferred in a similar situation: when the VTI ResultSet is scrollable (ResultSet.TYPE_SCROLL_SENSITIVE or TYPE_SCROLL_INSENSITIVE), and the where clause contains a subselect on a VTI from the same class as the target VTI. We do not look at the VTI parameters, just the VTI class name.
By default, inserts into a VTI are deferred when the same VTI class is used as both the source and target. It does not depend on the scrollability of the VTI ResultSet because inserts can be deferred without scrolling the ResultSet.
If these defaults are not appropriate then the class implementing the VTI should also implement this interface (org.apache.derby.vti.DeferModification).
(A read/write VTI is implemented by a class that implements the java.sql.PreparedStatement interface, often by extending the UpdatableVTITemplate interface. @see UpdatableVTITemplate).
Update and delete statement deferral is implemented by scrolling the VTI's ResultSet. Therefore, updates and deletes on a VTI are never deferred unless the VTI's ResultSets are scrollable, even if the DeferModification interface methods return true. Therefore for an update or delete to be deferred the VTI getResultSetType() method must return ResultSet.TYPE_SCROLL_SENSITIVE or TYPE_SCROLL_INSENSITIVE and the VTI must produce scrollable java.sql.ResultSets that implement the getRow() and absolute() methods. If your VTI is implemented as an extension to UpdatableVTITemplate then you must override the getResultSetMethod: UpdatableVTITemplate.getResultSetType() throws an exception. If your VTI's ResultSets are implemented as extensions to VTITemplate then you must override the getRow() and absolute() methods: VTITemplate.getRow() and absolute() throw exceptions.
This interface is not used when the VTI is referenced only in a subselect; it is only used when a VTI appears as the target of an INSERT, UPDATE, or DELETE statement.

                                   QueryTreeNode source)
        throws StandardException
    {
        try
        {
            DeferModification deferralControl;
            int resultSetType = targetVTI.getResultSetType( );


            /* Deferred updates and deletes are implemented by scrolling the result set. So, if
             * the statement is an update or delete but the result set is not scrollable then do
             * not attempt to defer the statement.
             */
            if( (statementType == DeferModification.UPDATE_STATEMENT ||statementType == DeferModification.DELETE_STATEMENT)
                && resultSetType == ResultSet.TYPE_FORWARD_ONLY)
                return false;


            deferralControl = targetVTI.getDeferralControl();
            if( deferralControl == null)
            {
                String VTIClassName = targetVTI.getMethodCall().getJavaClassName();
                deferralControl = new DefaultVTIModDeferPolicy( VTIClassName,
                                                                ResultSet.TYPE_SCROLL_SENSITIVE == resultSetType);
            }
            if( deferralControl.alwaysDefer( statementType))
                return true;


            if( source == null && statementType != DeferModification.UPDATE_STATEMENT)
                return false;


            VTIDeferModPolicy deferralSearch = new VTIDeferModPolicy( targetVTI,
                                                                      updateColumnNames,
                                                                      deferralControl,
                                                                      statementType);


            if( source != null)
                source.accept( deferralSearch);


            if( statementType == DeferModification.UPDATE_STATEMENT)
            {
                // Apply the columnRequiresDefer method to updated columns not in the where clause.
                Enumeration columns = deferralSearch.columns.keys();
                while( columns.hasMoreElements())
                {
                    if( deferralControl.columnRequiresDefer( statementType,
                                                             (String) columns.nextElement(),
                                                             false))
                        return true;
                }
            }

View Full Code Here

                                   QueryTreeNode source)
        throws StandardException
    {
        try
        {
            DeferModification deferralControl;
            int resultSetType = targetVTI.getResultSetType( );


            /* Deferred updates and deletes are implemented by scrolling the result set. So, if
             * the statement is an update or delete but the result set is not scrollable then do
             * not attempt to defer the statement.
             */
            if( (statementType == DeferModification.UPDATE_STATEMENT ||statementType == DeferModification.DELETE_STATEMENT)
                && resultSetType == ResultSet.TYPE_FORWARD_ONLY)
                return false;


            deferralControl = targetVTI.getDeferralControl();
            if( deferralControl == null)
            {
                String VTIClassName = targetVTI.getMethodCall().getJavaClassName();
                deferralControl = new DefaultVTIModDeferPolicy( VTIClassName,
                                                                ResultSet.TYPE_SCROLL_SENSITIVE == resultSetType);
            }
            if( deferralControl.alwaysDefer( statementType))
                return true;


            if( source == null && statementType != DeferModification.UPDATE_STATEMENT)
                return false;


            VTIDeferModPolicy deferralSearch = new VTIDeferModPolicy( targetVTI,
                                                                      updateColumnNames,
                                                                      deferralControl,
                                                                      statementType);


            if( source != null)
                source.accept( deferralSearch);


            if( statementType == DeferModification.UPDATE_STATEMENT)
            {
                // Apply the columnRequiresDefer method to updated columns not in the where clause.
                for (String s : deferralSearch.columns) {
                    if (deferralControl.columnRequiresDefer(
                            statementType, s, false)) {
                        return true;
                    }
                }
            }

View Full Code Here

                                   QueryTreeNode source)
        throws StandardException
    {
        try
        {
            DeferModification deferralControl;
            int resultSetType = targetVTI.getResultSetType( );


            /* Deferred updates and deletes are implemented by scrolling the result set. So, if
             * the statement is an update or delete but the result set is not scrollable then do
             * not attempt to defer the statement.
             */
            if( (statementType == DeferModification.UPDATE_STATEMENT ||statementType == DeferModification.DELETE_STATEMENT)
                && resultSetType == ResultSet.TYPE_FORWARD_ONLY)
                return false;


            deferralControl = targetVTI.getDeferralControl();
            if( deferralControl == null)
            {
                String VTIClassName = targetVTI.getMethodCall().getJavaClassName();
                deferralControl = new DefaultVTIModDeferPolicy( VTIClassName,
                                                                ResultSet.TYPE_SCROLL_SENSITIVE == resultSetType);
            }
            if( deferralControl.alwaysDefer( statementType))
                return true;


            if( source == null && statementType != DeferModification.UPDATE_STATEMENT)
                return false;


            VTIDeferModPolicy deferralSearch = new VTIDeferModPolicy( targetVTI,
                                                                      updateColumnNames,
                                                                      deferralControl,
                                                                      statementType);


            if( source != null)
                source.accept( deferralSearch);


            if( statementType == DeferModification.UPDATE_STATEMENT)
            {
                // Apply the columnRequiresDefer method to updated columns not in the where clause.
                Iterator columns = deferralSearch.columns.iterator();
                while (columns.hasNext())
                {
                    if (deferralControl.columnRequiresDefer(
                            statementType, (String) columns.next(), false)) {
                        return true;
                    }
                }
            }

View Full Code Here

                                   QueryTreeNode source)
        throws StandardException
    {
        try
        {
            DeferModification deferralControl;
            int resultSetType = targetVTI.getResultSetType( );


            /* Deferred updates and deletes are implemented by scrolling the result set. So, if
             * the statement is an update or delete but the result set is not scrollable then do
             * not attempt to defer the statement.
             */
            if( (statementType == DeferModification.UPDATE_STATEMENT ||statementType == DeferModification.DELETE_STATEMENT)
                && resultSetType == ResultSet.TYPE_FORWARD_ONLY)
                return false;


            deferralControl = targetVTI.getDeferralControl();
            if( deferralControl == null)
            {
                String VTIClassName = targetVTI.getNewInvocation().getJavaClassName();
                deferralControl = new DefaultVTIModDeferPolicy( VTIClassName,
                                                                ResultSet.TYPE_SCROLL_SENSITIVE == resultSetType);
            }
            if( deferralControl.alwaysDefer( statementType))
                return true;


            if( source == null && statementType != DeferModification.UPDATE_STATEMENT)
                return false;


            VTIDeferModPolicy deferralSearch = new VTIDeferModPolicy( targetVTI,
                                                                      updateColumnNames,
                                                                      deferralControl,
                                                                      statementType);


            if( source != null)
                source.accept( deferralSearch);


            if( statementType == DeferModification.UPDATE_STATEMENT)
            {
                // Apply the columnRequiresDefer method to updated columns not in the where clause.
                Enumeration columns = deferralSearch.columns.keys();
                while( columns.hasMoreElements())
                {
                    if( deferralControl.columnRequiresDefer( statementType,
                                                             (String) columns.nextElement(),
                                                             false))
                        return true;
                }
            }

View Full Code Here

                                   QueryTreeNode source)
        throws StandardException
    {
        try
        {
            DeferModification deferralControl;
            int resultSetType = targetVTI.getResultSetType( );


            /* Deferred updates and deletes are implemented by scrolling the result set. So, if
             * the statement is an update or delete but the result set is not scrollable then do
             * not attempt to defer the statement.
             */
            if( (statementType == DeferModification.UPDATE_STATEMENT ||statementType == DeferModification.DELETE_STATEMENT)
                && resultSetType == ResultSet.TYPE_FORWARD_ONLY)
                return false;


            deferralControl = targetVTI.getDeferralControl();
            if( deferralControl == null)
            {
                String VTIClassName = targetVTI.getMethodCall().getJavaClassName();
                deferralControl = new DefaultVTIModDeferPolicy( VTIClassName,
                                                                ResultSet.TYPE_SCROLL_SENSITIVE == resultSetType);
            }
            if( deferralControl.alwaysDefer( statementType))
                return true;


            if( source == null && statementType != DeferModification.UPDATE_STATEMENT)
                return false;


            VTIDeferModPolicy deferralSearch = new VTIDeferModPolicy( targetVTI,
                                                                      updateColumnNames,
                                                                      deferralControl,
                                                                      statementType);


            if( source != null)
                source.accept( deferralSearch);


            if( statementType == DeferModification.UPDATE_STATEMENT)
            {
                // Apply the columnRequiresDefer method to updated columns not in the where clause.
                Enumeration columns = deferralSearch.columns.keys();
                while( columns.hasMoreElements())
                {
                    if( deferralControl.columnRequiresDefer( statementType,
                                                             (String) columns.nextElement(),
                                                             false))
                        return true;
                }
            }

View Full Code Here

                                   QueryTreeNode source)
        throws StandardException
    {
        try
        {
            DeferModification deferralControl;
            int resultSetType = targetVTI.getResultSetType( );


            /* Deferred updates and deletes are implemented by scrolling the result set. So, if
             * the statement is an update or delete but the result set is not scrollable then do
             * not attempt to defer the statement.
             */
            if( (statementType == DeferModification.UPDATE_STATEMENT ||statementType == DeferModification.DELETE_STATEMENT)
                && resultSetType == ResultSet.TYPE_FORWARD_ONLY)
                return false;


            deferralControl = targetVTI.getDeferralControl();
            if( deferralControl == null)
            {
                String VTIClassName = targetVTI.getNewInvocation().getJavaClassName();
                deferralControl = new DefaultVTIModDeferPolicy( VTIClassName,
                                                                ResultSet.TYPE_SCROLL_SENSITIVE == resultSetType);
            }
            if( deferralControl.alwaysDefer( statementType))
                return true;


            if( source == null && statementType != DeferModification.UPDATE_STATEMENT)
                return false;


            VTIDeferModPolicy deferralSearch = new VTIDeferModPolicy( targetVTI,
                                                                      updateColumnNames,
                                                                      deferralControl,
                                                                      statementType);


            if( source != null)
                source.accept( deferralSearch);


            if( statementType == DeferModification.UPDATE_STATEMENT)
            {
                // Apply the columnRequiresDefer method to updated columns not in the where clause.
                Enumeration columns = deferralSearch.columns.keys();
                while( columns.hasMoreElements())
                {
                    if( deferralControl.columnRequiresDefer( statementType,
                                                             (String) columns.nextElement(),
                                                             false))
                        return true;
                }
            }

View Full Code Here

TOP

Related Classes of org.apache.derby.vti.DeferModification

org.apache.derby.impl.sql.compile.VTIDeferModPolicy

All source code are property of their respective owners. Java is a trademark of Sun Microsystems, Inc and owned by ORACLE Inc. Contact coftware#gmail.com.