org.apache.derby.impl.sql.compile

Class CurrentOfNode

java.lang.Object

org.apache.derby.impl.sql.compile.QueryTreeNode

org.apache.derby.impl.sql.compile.ResultSetNode

org.apache.derby.impl.sql.compile.CurrentOfNode

All Implemented Interfaces:

Optimizable, Visitable

public final class CurrentOfNode
extends ResultSetNode

The CurrentOf operator is used by positioned DELETE and UPDATE to get the current row and location for the target cursor. The bind() operations for positioned DELETE and UPDATE add a column to the select list under the statement for the row location accessible from this node. This node is placed in the from clause of the select generated for the delete or update operation. It acts much like a FromBaseTable, using the information about the target table of the cursor to provide information.

Method Summary

Modifier and Type	Method and Description
boolean	considerSortAvoidancePath() Check whether this optimizable's sort avoidance path should be considered.
int	convertAbsoluteToRelativeColumnPosition(int absolutePosition) Convert an absolute to a relative 0-based column position.
CostEstimate	estimateCost(OptimizablePredicateList predList, ConglomerateDescriptor cd, CostEstimate outerCost, Optimizer optimizer, RowOrdering rowOrdering) Estimate the cost of scanning this Optimizable using the given predicate list with the given conglomerate.
boolean	feasibleJoinStrategy(OptimizablePredicateList predList, Optimizer optimizer) Is the current proposed join strategy for this optimizable feasible given the predicate list?
boolean	forUpdate() Return true if this is the target table of an update
java.lang.String	getBaseTableName() Get the table name of this Optimizable.
AccessPath	getBestAccessPath() Get the best access path for this Optimizable.
AccessPath	getBestSortAvoidancePath() Get the best sort-avoidance path for this Optimizable.
java.lang.String	getCorrelationName() Get this table's correlation name, if any.
AccessPath	getCurrentAccessPath() Get the current access path under consideration for this Optimizable
java.lang.String	getName() Get the (exposed) name of this Optimizable
int	getNumColumnsReturned() Get the number of the number of columns returned by this Optimizable.
java.util.Properties	getProperties() Get the Properties list, if any, associated with this optimizable.
TableDescriptor	getTableDescriptor() Get the table descriptor for this table (if any).
int	getTableNumber() Get this Optimizable's table number
AccessPath	getTrulyTheBestAccessPath() Get the best access path overall for this Optimizable.
int[]	hashKeyColumns() Return the hash key column numbers, for hash join strategy
boolean	hasLargeObjectColumns() Check if any columns containing large objects (BLOBs or CLOBs) are referenced in this table.
boolean	hasTableNumber() Return true if this Optimizable has a table number
void	initAccessPaths(Optimizer optimizer) Init the access paths for this optimizable.
int	initialCapacity() Return the initial capacity of the hash table, for hash join strategy
boolean	isBaseTable() Tell whether this Optimizable represents a base table
boolean	isCoveringIndex(ConglomerateDescriptor cd) Return whether or not this is a covering index.
boolean	isMaterializable() Tell whether this Optimizable is materializable
boolean	isOneRowScan() Will the optimizable return at most 1 row per scan?
boolean	isTargetTable() Is the optimizable the target table of an update or delete?
boolean	legalJoinOrder(JBitSet assignedTableMap) Can this Optimizable appear at the current location in the join order.
float	loadFactor() Return the load factor of the hash table, for hash join strategy
int	maxCapacity(JoinStrategy joinStrategy, int maxMemoryPerTable) Return the maximum capacity of the hash table, for hash join strategy
boolean	memoryUsageOK(double rowCount, int maxMemoryPerTable)
Optimizable	modifyAccessPath(JBitSet outerTables) Modify the access path for this Optimizable, as necessary.
boolean	nextAccessPath(Optimizer optimizer, OptimizablePredicateList predList, RowOrdering rowOrdering) Choose the next access path to evaluate for this Optimizable.
CostEstimate	optimizeIt(Optimizer optimizer, OptimizablePredicateList predList, CostEstimate outerCost, RowOrdering rowOrdering) Choose the best access path for this Optimizable.
void	pullOptPredicates(OptimizablePredicateList optimizablePredicates) Pull all the OptimizablePredicates from this Optimizable and put them in the given OptimizablePredicateList.
boolean	pushOptPredicate(OptimizablePredicate optimizablePredicate) Push an OptimizablePredicate down, if this node accepts it.
void	rememberAsBest(int planType, Optimizer optimizer) Remember the current access path as the best one (so far).
void	rememberJoinStrategyAsBest(AccessPath ap) Remember the current join strategy as the best one so far in this join order.
void	rememberSortAvoidancePath() Mark this optimizable so that its sort avoidance path will be considered.
void	setHashKeyColumns(int[] columnNumbers) Set the hash key column numbers, for hash join strategy
void	setProperties(java.util.Properties tableProperties) Set the Properties list for this optimizalbe.
void	startOptimizing(Optimizer optimizer, RowOrdering rowOrdering) Begin the optimization process for this Optimizable.
boolean	supportsMultipleInstantiations() Tell whether this Optimizable can be instantiated multiple times
java.lang.String	toString() Convert this object to a String.
double	uniqueJoin(OptimizablePredicateList predList) Does this optimizable have a uniqueness condition on the given predicate list, and if so, how many unique keys will be returned per scan.
void	updateBestPlanMap(short action, java.lang.Object planKey) When remembering "truly the best" access path for an Optimizable, we have to keep track of which OptimizerImpl the "truly the best" access is for.
int	updateTargetLockMode() Get the lock mode for this table as the target of an update statement (a delete or update).
void	verifyProperties(DataDictionary dDictionary) Verify that the Properties list with optimizer overrides, if specified, is valid

Methods inherited from class org.apache.derby.impl.sql.compile.ResultSetNode

getReferencedTableMap, getResultSetNumber, makeResultDescription, parseDefault

Methods inherited from class org.apache.derby.impl.sql.compile.QueryTreeNode

accept, addTag, bindOffsetFetch, bindRowMultiSet, bindUserCatalogType, bindUserType, checkReliability, checkReliability, createTypeDependency, getBeginOffset, getDataDictionary, getEndOffset, getExecutionFactory, getGenericConstantActionFactory, getOffsetOrderedNodes, getOptimizerFactory, getOptimizerTracer, getParameterTypes, getUDTDesc, isAtomic, makeConstantAction, makeTableName, makeTableName, optimizerTracingIsOn, orReliability, referencesSessionSchema, setBeginOffset, setEndOffset, taggedWith, treePrint

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.derby.iapi.sql.compile.Optimizable

getDataDictionary, getOptimizerTracer, getReferencedTableMap, getResultSetNumber, optimizerTracingIsOn

Methods inherited from interface org.apache.derby.iapi.sql.compile.Visitable

accept, addTag, taggedWith

Method Detail

estimateCost

public CostEstimate estimateCost(OptimizablePredicateList predList,
                                 ConglomerateDescriptor cd,
                                 CostEstimate outerCost,
                                 Optimizer optimizer,
                                 RowOrdering rowOrdering)
                          throws StandardException

Description copied from interface: Optimizable

Estimate the cost of scanning this Optimizable using the given predicate list with the given conglomerate. It is assumed that the predicate list has already been classified. This cost estimate is just for one scan, not for the life of the query.

Specified by:

estimateCost in interface Optimizable

Parameters:

predList - The predicate list to optimize against

cd - The conglomerate descriptor to get the cost of

outerCost - The estimated cost of the part of the plan outer to this optimizable.

optimizer - The optimizer to use to help estimate the cost

rowOrdering - The row ordering for all the tables in the join order, including this one.

Returns:

The estimated cost of doing the scan

Throws:

StandardException - Thrown on error

See Also:

Optimizable.estimateCost(org.apache.derby.iapi.sql.compile.OptimizablePredicateList, org.apache.derby.iapi.sql.dictionary.ConglomerateDescriptor, org.apache.derby.iapi.sql.compile.CostEstimate, org.apache.derby.iapi.sql.compile.Optimizer, org.apache.derby.iapi.sql.compile.RowOrdering)

toString

public java.lang.String toString()

Convert this object to a String. See comments in QueryTreeNode.java for how this should be done for tree printing.

Returns:

This object as a String

updateTargetLockMode

public int updateTargetLockMode()

Get the lock mode for this table as the target of an update statement (a delete or update). This is implemented only for base tables and CurrentOfNodes.

Returns:

The lock mode

See Also:

TransactionController

getCorrelationName

public java.lang.String getCorrelationName()

Get this table's correlation name, if any.

optimizeIt

public CostEstimate optimizeIt(Optimizer optimizer,
                               OptimizablePredicateList predList,
                               CostEstimate outerCost,
                               RowOrdering rowOrdering)
                        throws StandardException

Description copied from interface: Optimizable

Choose the best access path for this Optimizable.

Specified by:

optimizeIt in interface Optimizable

Parameters:

optimizer - Optimizer to use.

predList - The predicate list to optimize against

outerCost - The CostEstimate for the outer tables in the join order, telling how many times this Optimizable will be scanned.

rowOrdering - The row ordering for all the tables in the join order, including this one.

Returns:

The optimizer's estimated cost of the best access path.

Throws:

StandardException - Thrown on error

See Also:

Optimizable.optimizeIt(org.apache.derby.iapi.sql.compile.Optimizer, org.apache.derby.iapi.sql.compile.OptimizablePredicateList, org.apache.derby.iapi.sql.compile.CostEstimate, org.apache.derby.iapi.sql.compile.RowOrdering)

nextAccessPath

public boolean nextAccessPath(Optimizer optimizer,
                              OptimizablePredicateList predList,
                              RowOrdering rowOrdering)
                       throws StandardException

Description copied from interface: Optimizable

Choose the next access path to evaluate for this Optimizable.

Specified by:

nextAccessPath in interface Optimizable

Parameters:

optimizer - Optimizer to use.

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.

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.

Returns:

true means another access path was chosen, false means no more access paths to evaluate.

Throws:

StandardException - Thrown on error

See Also:

Optimizable.nextAccessPath(org.apache.derby.iapi.sql.compile.Optimizer, org.apache.derby.iapi.sql.compile.OptimizablePredicateList, org.apache.derby.iapi.sql.compile.RowOrdering)

getCurrentAccessPath

public AccessPath getCurrentAccessPath()

Description copied from interface: Optimizable

Get the current access path under consideration for this Optimizable

Specified by:

getCurrentAccessPath in interface Optimizable

See Also:

Optimizable.getCurrentAccessPath()

getBestAccessPath

public AccessPath getBestAccessPath()

Description copied from interface: Optimizable

Get the best access path for this Optimizable.

Specified by:

getBestAccessPath in interface Optimizable

See Also:

Optimizable.getBestAccessPath()

getBestSortAvoidancePath

public AccessPath getBestSortAvoidancePath()

Description copied from interface: Optimizable

Get the best sort-avoidance path for this Optimizable.

Specified by:

getBestSortAvoidancePath in interface Optimizable

See Also:

Optimizable.getBestSortAvoidancePath()

getTrulyTheBestAccessPath

public AccessPath getTrulyTheBestAccessPath()

Description copied from interface: Optimizable

Get the best access path overall for this Optimizable.

Specified by:

getTrulyTheBestAccessPath in interface Optimizable

See Also:

Optimizable.getTrulyTheBestAccessPath()

rememberSortAvoidancePath

public void rememberSortAvoidancePath()

Description copied from interface: Optimizable

Mark this optimizable so that its sort avoidance path will be considered.

Specified by:

rememberSortAvoidancePath in interface Optimizable

See Also:

Optimizable.rememberSortAvoidancePath()

considerSortAvoidancePath

public boolean considerSortAvoidancePath()

Description copied from interface: Optimizable

Check whether this optimizable's sort avoidance path should be considered.

Specified by:

considerSortAvoidancePath in interface Optimizable

See Also:

Optimizable.considerSortAvoidancePath()

rememberJoinStrategyAsBest

public void rememberJoinStrategyAsBest(AccessPath ap)

Description copied from interface: Optimizable

Remember the current join strategy as the best one so far in this join order.

Specified by:

rememberJoinStrategyAsBest in interface Optimizable

See Also:

Optimizable.rememberJoinStrategyAsBest(org.apache.derby.iapi.sql.compile.AccessPath)

getTableDescriptor

public TableDescriptor getTableDescriptor()

Description copied from interface: Optimizable

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.

Specified by:

getTableDescriptor in interface Optimizable

See Also:

Optimizable.getTableDescriptor()

pushOptPredicate

public boolean pushOptPredicate(OptimizablePredicate optimizablePredicate)
                         throws StandardException

Description copied from interface: Optimizable

Push an OptimizablePredicate down, if this node accepts it.

Specified by:

pushOptPredicate in interface Optimizable

Parameters:

optimizablePredicate - OptimizablePredicate to push down.

Returns:

Whether or not the predicate was pushed down.

Throws:

StandardException - Thrown on error

See Also:

Optimizable.pushOptPredicate(org.apache.derby.iapi.sql.compile.OptimizablePredicate)

pullOptPredicates

public void pullOptPredicates(OptimizablePredicateList optimizablePredicates)
                       throws StandardException

Description copied from interface: Optimizable

Pull all the OptimizablePredicates from this Optimizable and put them in the given OptimizablePredicateList.

Specified by:

pullOptPredicates in interface Optimizable

Parameters:

optimizablePredicates - The list to put the pulled predicates in.

Throws:

StandardException - Thrown on error

See Also:

Optimizable.pullOptPredicates(org.apache.derby.iapi.sql.compile.OptimizablePredicateList)

modifyAccessPath

public Optimizable modifyAccessPath(JBitSet outerTables)
                             throws StandardException

Description copied from interface: Optimizable

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

Specified by:

modifyAccessPath in interface Optimizable

Parameters:

outerTables - Bit map of the tables that are outer to this one in the join order.

Returns:

The (potentially new) Optimizable at the top of the tree.

Throws:

StandardException - Thrown on error

See Also:

Optimizable.modifyAccessPath(org.apache.derby.iapi.util.JBitSet)

isCoveringIndex

public boolean isCoveringIndex(ConglomerateDescriptor cd)
                        throws StandardException

Description copied from interface: Optimizable

Return whether or not this is a covering index. We expect to call this during generation, after access path selection is complete.

Specified by:

isCoveringIndex in interface Optimizable

Parameters:

cd - ConglomerateDesriptor for index to consider

Returns:

boolean Whether or not this is a covering index.

Throws:

StandardException - Thrown on error

See Also:

Optimizable.isCoveringIndex(org.apache.derby.iapi.sql.dictionary.ConglomerateDescriptor)

getProperties

public java.util.Properties getProperties()

Description copied from interface: Optimizable

Get the Properties list, if any, associated with this optimizable.

Specified by:

getProperties in interface Optimizable

Returns:

The Properties list, if any, associated with this optimizable.

See Also:

Optimizable.getProperties()

setProperties

public void setProperties(java.util.Properties tableProperties)

Description copied from interface: Optimizable

Set the Properties list for this optimizalbe.

Specified by:

setProperties in interface Optimizable

Parameters:

tableProperties - The Properties list for this optimizable.

See Also:

Optimizable.setProperties(java.util.Properties)

verifyProperties

public void verifyProperties(DataDictionary dDictionary)
                      throws StandardException

Description copied from interface: Optimizable

Verify that the Properties list with optimizer overrides, if specified, is valid

Specified by:

verifyProperties in interface Optimizable

Parameters:

dDictionary - The DataDictionary to use.

Throws:

StandardException - Thrown on error

See Also:

Optimizable.verifyProperties(org.apache.derby.iapi.sql.dictionary.DataDictionary)

getName

public java.lang.String getName()
                         throws StandardException

Description copied from interface: Optimizable

Get the (exposed) name of this Optimizable

Specified by:

getName in interface Optimizable

Returns:

The name of this Optimizable.

Throws:

StandardException - Thrown on error

See Also:

Optimizable.getName()

getBaseTableName

public java.lang.String getBaseTableName()

Description copied from interface: Optimizable

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).

Specified by:

getBaseTableName in interface Optimizable

See Also:

Optimizable.getBaseTableName()

convertAbsoluteToRelativeColumnPosition

public int convertAbsoluteToRelativeColumnPosition(int absolutePosition)

Description copied from interface: Optimizable

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

Specified by:

convertAbsoluteToRelativeColumnPosition in interface Optimizable

Parameters:

absolutePosition - The absolute 0-based column position for the column.

Returns:

The relative 0-based column position for the column.

See Also:

Optimizable.convertAbsoluteToRelativeColumnPosition(int)

updateBestPlanMap

public void updateBestPlanMap(short action,
                              java.lang.Object planKey)
                       throws StandardException

Description copied from interface: Optimizable

When remembering "truly the best" access path for an Optimizable, we have to keep track of which OptimizerImpl the "truly the best" access is for. In most queries there will only be one OptimizerImpl in question, but in cases where there are nested subqueries, there will be one OptimizerImpl for every level of nesting, and each OptimizerImpl might have its own idea of what this Optimizable's "truly the best path" access path really is. In addition, there could be Optimizables above this Optimizable that might need to override the best path chosen during optimization. So whenever we save a "truly the best" path, we take note of which Optimizer/Optimizable told us to do so. Then as each level of subquery finishes optimization, the corresponding OptimizerImpl/Optimizable can load its preferred access path into this Optimizable's trulyTheBestAccessPath field and pass it up the tree, until eventually the outer-most OptimizerImpl can choose to either use the best path that it received from below (by calling "rememberAsBest()") or else use the path that it found to be "best" for itself. This method is what allows us to keep track of which OptimizerImpl or Optimizable saved which "best plan", and allows us to load the appropriate plans after each round of optimization.

Specified by:

updateBestPlanMap in interface Optimizable

Parameters:

action - Indicates whether we're adding, loading, or removing a best plan for the OptimizerImpl/Optimizable.

planKey - Object to use as the map key when adding/looking up a plan. If it is an instance of OptimizerImpl then it corresponds to an outer query; otherwise it's some Optimizable above this Optimizable that could potentially reject plans chosen by the OptimizerImpl to which this Optimizable belongs.

Throws:

StandardException

See Also:

Optimizable.updateBestPlanMap(short, java.lang.Object)

rememberAsBest

public void rememberAsBest(int planType,
                           Optimizer optimizer)
                    throws StandardException

Description copied from interface: Optimizable

Remember the current access path as the best one (so far).

Specified by:

rememberAsBest in interface Optimizable

Parameters:

planType - The type of plan (one of Optimizer.NORMAL_PLAN or Optimizer.SORT_AVOIDANCE_PLAN)

optimizer - The OptimizerImpl that is telling this Optimizable to remember its current path as "truly the best".

Throws:

StandardException - thrown on error.

See Also:

Optimizable.rememberAsBest(int, org.apache.derby.iapi.sql.compile.Optimizer)

startOptimizing

public void startOptimizing(Optimizer optimizer,
                            RowOrdering rowOrdering)

Description copied from interface: Optimizable

Begin the optimization process for this Optimizable. This can be called many times for an Optimizable while optimizing a query - it will typically be called every time the Optimizable is placed in a potential join order.

Specified by:

startOptimizing in interface Optimizable

See Also:

Optimizable.startOptimizing(org.apache.derby.iapi.sql.compile.Optimizer, org.apache.derby.iapi.sql.compile.RowOrdering)

isBaseTable

public boolean isBaseTable()

Description copied from interface: Optimizable

Tell whether this Optimizable represents a base table

Specified by:

isBaseTable in interface Optimizable

See Also:

Optimizable.isBaseTable()

hasLargeObjectColumns

public boolean hasLargeObjectColumns()

Check if any columns containing large objects (BLOBs or CLOBs) are referenced in this table.

Specified by:

hasLargeObjectColumns in interface Optimizable

Returns:

true if at least one large object column is referenced, false otherwise

isMaterializable

public boolean isMaterializable()
                         throws StandardException

Description copied from interface: Optimizable

Tell whether this Optimizable is materializable

Specified by:

isMaterializable in interface Optimizable

Throws:

StandardException - Thrown on error

See Also:

Optimizable.isMaterializable()

supportsMultipleInstantiations

public boolean supportsMultipleInstantiations()

Description copied from interface: Optimizable

Tell whether this Optimizable can be instantiated multiple times

Specified by:

supportsMultipleInstantiations in interface Optimizable

See Also:

Optimizable.supportsMultipleInstantiations()

getTableNumber

public int getTableNumber()

Description copied from interface: Optimizable

Get this Optimizable's table number

Specified by:

getTableNumber in interface Optimizable

See Also:

Optimizable.getTableNumber()

hasTableNumber

public boolean hasTableNumber()

Description copied from interface: Optimizable

Return true if this Optimizable has a table number

Specified by:

hasTableNumber in interface Optimizable

See Also:

Optimizable.hasTableNumber()

forUpdate

public boolean forUpdate()

Description copied from interface: Optimizable

Return true if this is the target table of an update

Specified by:

forUpdate in interface Optimizable

See Also:

Optimizable.forUpdate()

initialCapacity

public int initialCapacity()

Description copied from interface: Optimizable

Return the initial capacity of the hash table, for hash join strategy

Specified by:

initialCapacity in interface Optimizable

See Also:

Optimizable.initialCapacity()

loadFactor

public float loadFactor()

Description copied from interface: Optimizable

Return the load factor of the hash table, for hash join strategy

Specified by:

loadFactor in interface Optimizable

See Also:

Optimizable.loadFactor()

maxCapacity

public int maxCapacity(JoinStrategy joinStrategy,
                       int maxMemoryPerTable)
                throws StandardException

Description copied from interface: Optimizable

Return the maximum capacity of the hash table, for hash join strategy

Specified by:

maxCapacity in interface Optimizable

maxMemoryPerTable - The maximum number of bytes to be used. Ignored if the user has set a maximum number of rows for the Optimizable.

Throws:

StandardException - Standard error policy

See Also:

Optimizable.maxCapacity(org.apache.derby.iapi.sql.compile.JoinStrategy, int)

hashKeyColumns

public int[] hashKeyColumns()

Description copied from interface: Optimizable

Return the hash key column numbers, for hash join strategy

Specified by:

hashKeyColumns in interface Optimizable

See Also:

Optimizable.hashKeyColumns()

setHashKeyColumns

public void setHashKeyColumns(int[] columnNumbers)

Description copied from interface: Optimizable

Set the hash key column numbers, for hash join strategy

Specified by:

setHashKeyColumns in interface Optimizable

See Also:

Optimizable.setHashKeyColumns(int[])

feasibleJoinStrategy

public boolean feasibleJoinStrategy(OptimizablePredicateList predList,
                                    Optimizer optimizer)
                             throws StandardException

Description copied from interface: Optimizable

Is the current proposed join strategy for this optimizable feasible given the predicate list?

Specified by:

feasibleJoinStrategy in interface Optimizable

Parameters:

predList - The predicate list that has been pushed down to this optimizable

optimizer - The optimizer to use.

Returns:

true means feasible

Throws:

StandardException - Thrown on error

See Also:

Optimizable.feasibleJoinStrategy(org.apache.derby.iapi.sql.compile.OptimizablePredicateList, org.apache.derby.iapi.sql.compile.Optimizer)

memoryUsageOK

public boolean memoryUsageOK(double rowCount,
                             int maxMemoryPerTable)
                      throws StandardException

Specified by:

memoryUsageOK in interface Optimizable

Returns:

true if the memory usage of the proposed access path is OK, false if not.

Throws:

StandardException - standard error policy

See Also:

Optimizable.memoryUsageOK(double, int)

legalJoinOrder

public boolean legalJoinOrder(JBitSet assignedTableMap)

Description copied from interface: Optimizable

Can this Optimizable appear at the current location in the join order. In other words, have the Optimizable's dependencies been satisfied?

Specified by:

legalJoinOrder in interface Optimizable

Parameters:

assignedTableMap - The tables that have been placed so far in the join order.

Returns:

Where or not this Optimizable can appear at the current location in the join order.

See Also:

Optimizable.legalJoinOrder(org.apache.derby.iapi.util.JBitSet)

getNumColumnsReturned

public int getNumColumnsReturned()

Description copied from interface: Optimizable

Get the number of the number of columns returned by this Optimizable.

Specified by:

getNumColumnsReturned in interface Optimizable

Returns:

The number of the number of columns returned by this Optimizable.

See Also:

Optimizable.getNumColumnsReturned()

isTargetTable

public boolean isTargetTable()

Description copied from interface: Optimizable

Is the optimizable the target table of an update or delete?

Specified by:

isTargetTable in interface Optimizable

Returns:

Whether or not the optimizable the target table of an update or delete.

See Also:

Optimizable.isTargetTable()

isOneRowScan

public boolean isOneRowScan()
                     throws StandardException

Description copied from interface: Optimizable

Will the optimizable return at most 1 row per scan?

Specified by:

isOneRowScan in interface Optimizable

Returns:

Whether or not the optimizable will return at most 1 row per scan?

Throws:

StandardException - Thrown on error

See Also:

Optimizable.isOneRowScan()

initAccessPaths

public void initAccessPaths(Optimizer optimizer)

Description copied from interface: Optimizable

Init the access paths for this optimizable.

Specified by:

initAccessPaths in interface Optimizable

Parameters:

optimizer - The optimizer being used.

See Also:

Optimizable.initAccessPaths(org.apache.derby.iapi.sql.compile.Optimizer)

uniqueJoin

public double uniqueJoin(OptimizablePredicateList predList)
                  throws StandardException

Description copied from interface: Optimizable

Does this optimizable have a uniqueness condition on the given predicate list, and if so, how many unique keys will be returned per scan.

Specified by:

uniqueJoin in interface Optimizable

Parameters:

predList - The predicate list to check

Returns:

<= 0 means there is no uniqueness condition > 0 means there is a uniqueness condition, and the return value is the number of rows per scan.

Throws:

StandardException - Thrown on error

See Also:

Optimizable.uniqueJoin(org.apache.derby.iapi.sql.compile.OptimizablePredicateList)