Class DistinctNode

java.lang.Object

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

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

org.apache.derby.impl.sql.compile.FromTable

org.apache.derby.impl.sql.compile.SingleChildResultSetNode

org.apache.derby.impl.sql.compile.DistinctNode

All Implemented Interfaces:

Optimizable, Visitable

class DistinctNode
extends SingleChildResultSetNode

A DistinctNode represents a result set for a distinct operation on a select. It has the same description as its input result set. For the most part, it simply delegates operations to its childResultSet, which is currently expected to be a ProjectRestrictResultSet generated for a SelectNode. NOTE: A DistinctNode extends FromTable since it can exist in a FromList.

Nested Class Summary

Nested classes/interfaces inherited from class ResultSetNode

ResultSetNode.QueryExpressionClauses

Field Summary

Fields

Modifier and Type	Field	Description
(package private) boolean	inSortedOrder

Fields inherited from class SingleChildResultSetNode

childResult, hasTrulyTheBestAccessPath

Fields inherited from class FromTable

ADD_PLAN, bestAccessPath, bestCostEstimate, bestSortAvoidancePath, correlationName, corrTableName, currentAccessPath, hashKeyColumns, initialCapacity, level, LOAD_PLAN, loadFactor, maxCapacity, origTableName, REMOVE_PLAN, tableNumber, tableProperties, trulyTheBestAccessPath, userSpecifiedJoinStrategy

Fields inherited from class QueryTreeNode

AUTOINCREMENT_CREATE_MODIFY, AUTOINCREMENT_CYCLE, AUTOINCREMENT_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX

Constructor Summary

Constructors

Constructor	Description
DistinctNode(ResultSetNode childResult, boolean inSortedOrder, Properties tableProperties, ContextManager cm)	Constructor for a DistinctNode.

Method Summary

Modifier and Type	Method	Description
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.
(package private) void	generate(ActivationClassBuilder acb, MethodBuilder mb)	generate the distinct result set operating over the source result set.
(package private) boolean	isOrderedOn(ColumnReference[] crs, boolean permuteOrdering, List<FromBaseTable> fbtHolder)	Return whether or not the underlying ResultSet tree is ordered on the specified columns.
(package private) ResultSetNode	optimize(DataDictionary dataDictionary, PredicateList predicates, double outerRows)	Optimize this DistinctNode.
CostEstimate	optimizeIt(Optimizer optimizer, OptimizablePredicateList predList, CostEstimate outerCost, RowOrdering rowOrdering)	Choose the best access path for this Optimizable.
boolean	pushOptPredicate(OptimizablePredicate optimizablePredicate)	Push an OptimizablePredicate down, if this node accepts it.

Methods inherited from class SingleChildResultSetNode

acceptChildren, addNewPredicate, adjustForSortElimination, adjustForSortElimination, changeAccessPath, decrementLevel, ensurePredicateList, flattenableInFromSubquery, forUpdate, getChildResult, getFinalCostEstimate, getFromTableByName, getTrulyTheBestAccessPath, initAccessPaths, isNotExists, isOneRowResultSet, modifyAccessPaths, preprocess, printSubNodes, pullOptPredicates, pushExpressions, referencesSessionSchema, referencesTarget, reflectionNeededForProjection, setChildResult, setLevel, subqueryReferencesTarget, updateBestPlanMap, updateTargetLockMode

Methods inherited from class FromTable

assignCostEstimate, canBeOrdered, columnsAreUpdatable, considerSortAvoidancePath, convertAbsoluteToRelativeColumnPosition, cursorTargetTable, feasibleJoinStrategy, fillInReferencedTableMap, flatten, getBaseTableName, getBestAccessPath, getBestSortAvoidancePath, getCorrelationName, getCostEstimate, getCurrentAccessPath, getExposedName, getLevel, getMergeTableID, getName, getNumColumnsReturned, getOrigTableName, getProperties, getResultColumnsForList, getSchemaDescriptor, getSchemaDescriptor, getScratchCostEstimate, getTableDescriptor, getTableName, getTableNumber, getUserSpecifiedJoinStrategy, hashKeyColumns, hasLargeObjectColumns, hasTableNumber, initialCapacity, isBaseTable, isCoveringIndex, isFlattenableJoinNode, isJoinColumnForRightOuterJoin, isMaterializable, isOneRowScan, isTargetTable, legalJoinOrder, loadFactor, LOJ_reorderable, markUpdatableByCursor, maxCapacity, memoryUsageOK, modifyAccessPath, needsSpecialRCLBinding, nextAccessPath, optimizeSubqueries, rememberAsBest, rememberJoinStrategyAsBest, rememberSortAvoidancePath, resetJoinStrategies, setCostEstimateCost, setHashKeyColumns, setMergeTableID, setOrigTableName, setProperties, setTableNumber, startOptimizing, supportsMultipleInstantiations, tellRowOrderingAboutConstantColumns, toString, transformOuterJoins, uniqueJoin, verifyProperties

Methods inherited from class ResultSetNode

assignResultSetNumber, bindExpressions, bindExpressionsWithTables, bindNonVTITables, bindResultColumns, bindResultColumns, bindTargetExpressions, bindUntypedNullsToResultColumns, bindVTITables, columnTypesAndLengthsMatch, considerMaterialization, enhanceRCLForInsert, generateNormalizationResultSet, generateResultSet, genProjectRestrict, genProjectRestrict, genProjectRestrictForReordering, getAllResultColumns, getCandidateFinalCostEstimate, getCostEstimate, getCursorTargetTable, getFromList, getMatchingColumn, getNewCostEstimate, getOptimizer, getOptimizerImpl, getRCLForInsert, getReferencedTableMap, getResultColumns, getResultSetNumber, getScratchCostEstimate, isCursorTargetTable, isInsertSource, isPossibleDistinctScan, isStatementResultSet, isUpdatableCursor, LOJgetReferencedTables, makeResultDescription, makeResultDescriptors, markAsCursorTargetTable, markForDistinctScan, markStatementResultSet, modifyAccessPaths, notCursorTargetTable, notFlattenableJoin, numDistinctAggregates, parseDefault, performMaterialization, printQueryExpressionSuffixClauses, projectResultColumns, pushOffsetFetchFirst, pushOrderByList, pushQueryExpressionSuffix, rejectParameters, rejectXMLValues, renameGeneratedResultNames, replaceOrForbidDefaults, returnsAtMostOneRow, setCandidateFinalCostEstimate, setCostEstimate, setCursorTargetTable, setInsertSource, setOptimizer, setReferencedTableMap, setResultColumns, setResultSetNumber, setResultToBooleanTrueNode, setScratchCostEstimate, setTableConstructorTypes, verifySelectStarSubquery

Methods inherited from class QueryTreeNode

accept, addTag, addUDTUsagePriv, addUDTUsagePriv, bindOffsetFetch, bindRowMultiSet, bindUserCatalogType, bindUserType, checkReliability, checkReliability, convertDefaultNode, copyTagsFrom, createTypeDependency, debugFlush, debugPrint, disablePrivilegeCollection, formatNodeString, generateAuthorizeCheck, getBeginOffset, getClassFactory, getCompilerContext, getContext, getContextManager, getDataDictionary, getDependencyManager, getEndOffset, getExecutionFactory, getGenericConstantActionFactory, getIntProperty, getLanguageConnectionContext, getLongProperty, getNullNode, getOffsetOrderedNodes, getOptimizerFactory, getOptimizerTracer, getParameterTypes, getSchemaDescriptor, getSchemaDescriptor, getStatementType, getTableDescriptor, getTypeCompiler, getUDTDesc, isAtomic, isPrivilegeCollectionRequired, isSessionSchema, isSessionSchema, makeConstantAction, makeTableName, makeTableName, nodeHeader, optimizerTracingIsOn, orReliability, parseSearchCondition, parseStatement, printLabel, resolveTableToSynonym, setBeginOffset, setEndOffset, setRefActionInfo, stackPrint, taggedWith, treePrint, treePrint, verifyClassExist

Methods inherited from class Object

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

Methods inherited from interface Optimizable

getDataDictionary, getOptimizerTracer, getReferencedTableMap, getResultSetNumber, optimizerTracingIsOn

Methods inherited from interface Visitable

accept, addTag, taggedWith

Field Details

inSortedOrder

boolean inSortedOrder

Constructor Details

DistinctNode

DistinctNode(ResultSetNode childResult,
 boolean inSortedOrder,
 Properties tableProperties,
 ContextManager cm)
      throws StandardException

Constructor for a DistinctNode.

Parameters:

childResult - The child ResultSetNode

inSortedOrder - Whether or not the child ResultSetNode returns its output in sorted order.

tableProperties - Properties list associated with the table

cm - The context manager

Throws:

StandardException - Thrown on error

Method Details

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

Overrides:

optimizeIt in class FromTable

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(Optimizer, OptimizablePredicateList, CostEstimate, RowOrdering)

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

Overrides:

estimateCost in class FromTable

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(OptimizablePredicateList, ConglomerateDescriptor, CostEstimate, Optimizer, RowOrdering)

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

Overrides:

pushOptPredicate in class FromTable

Parameters:

optimizablePredicate - OptimizablePredicate to push down.

Returns:

Whether or not the predicate was pushed down.

Throws:

StandardException - Thrown on error

See Also:

• Optimizable.pushOptPredicate(OptimizablePredicate)

optimize

ResultSetNode optimize(DataDictionary dataDictionary,
 PredicateList predicates,
 double outerRows)
                throws StandardException

Optimize this DistinctNode.

Overrides:

optimize in class SingleChildResultSetNode

Parameters:

dataDictionary - The DataDictionary to use for optimization

predicates - The PredicateList to optimize. This should be a join predicate.

outerRows - The number of outer joining rows

Returns:

ResultSetNode The top of the optimized subtree

Throws:

StandardException - Thrown on error

isOrderedOn

boolean isOrderedOn(ColumnReference[] crs,
 boolean permuteOrdering,
 List<FromBaseTable> fbtHolder)

Return whether or not the underlying ResultSet tree is ordered on the specified columns. RESOLVE - This method currently only considers the outermost table of the query block.

Overrides:

isOrderedOn in class SingleChildResultSetNode

Parameters:

crs - The specified ColumnReference[]

permuteOrdering - Whether or not the order of the CRs in the array can be permuted

fbtHolder - List that is to be filled with the FromBaseTable

Returns:

Whether the underlying ResultSet tree is ordered on the specified column.

generate

void generate(ActivationClassBuilder acb,
 MethodBuilder mb)
       throws StandardException

generate the distinct result set operating over the source result set.

Overrides:

generate in class QueryTreeNode

Parameters:

acb - The ActivationClassBuilder for the class being built

mb - The method for the generated code to go into

Throws:

StandardException - Thrown on error