optimizable.java

derby database source code.good for you.

/*

   Derby - Class org.apache.derby.iapi.sql.compile.Optimizable

   Copyright 1997, 2004 The Apache Software Foundation or its licensors, as applicable.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */

package org.apache.derby.iapi.sql.compile;

import org.apache.derby.iapi.sql.dictionary.ConglomerateDescriptor;
import org.apache.derby.iapi.sql.dictionary.TableDescriptor;
import org.apache.derby.iapi.sql.dictionary.DataDictionary;

import org.apache.derby.iapi.error.StandardException;

import org.apache.derby.iapi.util.JBitSet;

import java.util.Properties;

/**
 * Optimizable provides services for optimizing a table in a query.
 */

public interface Optimizable {

	/**
	 * Choose the next access path to evaluate for this Optimizable.
	 *
	 * @param optimizer	Optimizer to use.
	 * @param predList	The predicate list for this optimizable.
	 *					The optimizer always passes null, and it is up
	 *					to the optimizable object to pass along its
	 *					own predicate list, if appropriate, when delegating
	 *					this method.
	 * @param rowOrdering	The row ordering for all the outer tables in
	 *						the join order.  This method will add the ordering
	 *						of the next access path to the given RowOrdering.
	 *
	 * @return	true means another access path was chosen, false means
	 *			no more access paths to evaluate.
	 *
	 * @exception StandardException		Thrown on error
	 */
	boolean nextAccessPath(Optimizer optimizer,
							OptimizablePredicateList predList,
							RowOrdering rowOrdering)
			throws StandardException;

	/**
	 * Choose the best access path for this Optimizable.
	 *
	 * @param optimizer	Optimizer to use.
	 * @param predList	The predicate list to optimize against
	 * @param outerCost	The CostEstimate for the outer tables in the join order,
	 *					telling how many times this Optimizable will be scanned.
	 * @param	rowOrdering The row ordering for all the tables in the
	 *						join order, including this one.
	 *
	 * @return The optimizer's estimated cost of the best access path.
	 *
	 * @exception StandardException		Thrown on error
	 */
	CostEstimate optimizeIt(
					Optimizer optimizer,
					OptimizablePredicateList predList,
					CostEstimate outerCost,
					RowOrdering rowOrdering)
				throws StandardException;

	/**
	 * Get the current access path under consideration for this Optimizable
	 */
	AccessPath getCurrentAccessPath();

	/**
	 * Get the best access path for this Optimizable.
	 */
	AccessPath getBestAccessPath();

	/**
	 * Get the best sort-avoidance path for this Optimizable.
	 */
	AccessPath getBestSortAvoidancePath();

	/**
	 * Get the best access path overall for this Optimizable.
	 */
	AccessPath getTrulyTheBestAccessPath();

	/**
	 * Mark this optimizable so that its sort avoidance path will be
	 * considered.
	 */
	void rememberSortAvoidancePath();

	/**
	 * Check whether this optimizable's sort avoidance path should
	 * be considered.
	 */
	boolean considerSortAvoidancePath();

	/**
	 * Remember the current join strategy as the best one so far in this
	 * join order.
	 */
	void rememberJoinStrategyAsBest(AccessPath ap);

	/**
	 * Get the table descriptor for this table (if any).  Only base tables
	 * have table descriptors - for the rest of the optimizables, this
	 * method returns null.
	 */
	TableDescriptor getTableDescriptor();

	/**
	 * Get the map of referenced tables for this Optimizable.
	 *
	 * @return JBitSet	Referenced table map.
	 */
	JBitSet getReferencedTableMap();

	/**
	 * Push an OptimizablePredicate down, if this node accepts it.
	 *
	 * @param optPred	OptimizablePredicate to push down.
	 *
	 * @return Whether or not the predicate was pushed down.
	 *
	 * @exception StandardException		Thrown on error
	 */
	boolean pushOptPredicate(OptimizablePredicate optimizablePredicate)
			throws StandardException;

	/**
	 * Pull all the OptimizablePredicates from this Optimizable and put them
	 * in the given OptimizablePredicateList.
	 *
	 * @param optimizablePredicates		The list to put the pulled predicates
	 *									in.
	 *
	 * @exception StandardException		Thrown on error
	 */
	void pullOptPredicates(OptimizablePredicateList optimizablePredicates)
			throws StandardException;

	/**
	 * Modify the access path for this Optimizable, as necessary.  This includes
	 * things like adding a result set to translate from index rows to base rows
	 *
	 * @param outerTables	Bit map of the tables that are outer to this one
	 *						in the join order.
	 * 
	 * @return	The (potentially new) Optimizable at the top of the tree.
	 *
	 * @exception StandardException		Thrown on error
	 */
	Optimizable modifyAccessPath(JBitSet outerTables) throws StandardException;

	/**
	 * Return whether or not this is a covering index.  We expect to call this
	 * during generation, after access path selection is complete.
	 *
	 * @param cd			ConglomerateDesriptor for index to consider
	 *
	 * @return boolean		Whether or not this is a covering index.
	 *
	 * @exception StandardException		Thrown on error
	 */
	public boolean isCoveringIndex(ConglomerateDescriptor cd) throws StandardException;

	/**
	 * Get the Properties list, if any, associated with this optimizalbe.
	 *
	 * @return The Properties list, if any, associated with this optimizable.
	 */
	public Properties getProperties();

	/**
	 * Set the Properties list for this optimizalbe.
	 *
	 * @param tableProperties The Properties list for this optimizable.
	 *
	 * @return Nothing.
	 */
	public void setProperties(Properties tableProperties);

	/** 
	 * Verify that the Properties list with optimizer overrides, if specified, is valid
	 *
	 * @param dDictionary	The DataDictionary  to use.
	 *
	 * @return Nothing.
	 * @exception StandardException		Thrown on error
	 */
	public void verifyProperties(DataDictionary dDictionary) throws StandardException;

	/**
	 * Get the (exposed) name of this Optimizable
	 *
	 * @return	The name of this Optimizable.
	 * @exception StandardException		Thrown on error
	 */
	public String getName() throws StandardException;

	/**
	 * Get the table name of this Optimizable.  Only base tables have
	 * table names (by the time we use this method, all views will have
	 * been resolved).
	 */
	public String getBaseTableName();

	/** 
	 *  Convert an absolute to a relative 0-based column position.
	 *  This is useful when generating qualifiers for partial rows 
	 *  from the store.
	 *