Class GroupByNode
- All Implemented Interfaces:
Optimizable
,Visitable
For the most part, it simply delegates operations to its bottomPRSet, which is currently expected to be a ProjectRestrictResultSet generated for a SelectNode.
NOTE: A GroupByNode extends FromTable since it can exist in a FromList.
There is a lot of room for optimizations here:
- agg(distinct x) group by x => agg(x) group by x (for min and max)
- min()/max() use index scans if possible, no sort may be needed.
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprivate static class
Comparator class for GROUP BY expression substitution.Nested classes/interfaces inherited from class org.apache.derby.impl.sql.compile.ResultSetNode
ResultSetNode.QueryExpressionClauses
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate boolean
private int
private AggregatorInfoList
Information that is used at execution time to process aggregates.private List
<AggregateNode> The list of all aggregates in the query block that contains this group by.(package private) GroupByList
The GROUP BY listprivate ValueNode
private SubqueryList
private final boolean
(package private) FromTable
The parent to the GroupByNode.private boolean
Fields inherited from class org.apache.derby.impl.sql.compile.SingleChildResultSetNode
childResult, hasTrulyTheBestAccessPath
Fields inherited from class org.apache.derby.impl.sql.compile.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 org.apache.derby.impl.sql.compile.QueryTreeNode
AUTOINCREMENT_CREATE_MODIFY, AUTOINCREMENT_CYCLE, AUTOINCREMENT_INC_INDEX, AUTOINCREMENT_IS_AUTOINCREMENT_INDEX, AUTOINCREMENT_START_INDEX
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Constructor Summary
ConstructorsConstructorDescriptionGroupByNode
(ResultSetNode bottomPR, GroupByList groupingList, List<AggregateNode> aggregates, ValueNode havingClause, SubqueryList havingSubquerys, int nestingLevel, ContextManager cm) Constructor for a GroupByNode. -
Method Summary
Modifier and TypeMethodDescriptionprivate void
In the query rewrite involving aggregates, add the columns for aggregation.private void
Add the extra result columns required by the aggregates to the result list.private void
Add any distinct aggregates to the order by list.private void
Add a whole slew of columns needed for aggregation.private void
Add a new PR node for aggregation.private ArrayList
<SubstituteExpressionVisitor> In the query rewrite for group by, add the columns on which we are doing the group by.(package private) void
considerPostOptimizeOptimizations
(boolean selectHasPredicates) Consider any optimizations after the optimizer has chosen a plan.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) boolean
flattenableInFromSubquery
(FromList fromList) Evaluate whether or not the subquery in a FromSubquery is flattenable.(package private) void
generate
(ActivationClassBuilder acb, MethodBuilder mb) generate the sort result set operating over the source result set.private void
Generate the code to evaluate grouped aggregates.private void
Generate the code to evaluate scalar aggregates.private ResultColumn
getColumnReference
(ResultColumn targetRC, DataDictionary dd) Method for creating a new result column referencing the one passed in.(package private) boolean
Get whether or not the source is in sorted order.(package private) final FromTable
Return the parent node to this one, if there is one.(package private) boolean
Return whether or not the underlying ResultSet tree will return a single row, at most.(package private) ResultColumnDescriptor[]
(package private) ResultSetNode
optimize
(DataDictionary dataDictionary, PredicateList predicates, double outerRows) Optimize this GroupByNode.optimizeIt
(Optimizer optimizer, OptimizablePredicateList predList, CostEstimate outerCost, RowOrdering rowOrdering) Choose the best access path for this Optimizable.(package private) void
printSubNodes
(int depth) Prints the sub-nodes of this object.boolean
pushOptPredicate
(OptimizablePredicate optimizablePredicate) Push an OptimizablePredicate down, if this node accepts it.toString()
Convert this object to a String.Methods inherited from class org.apache.derby.impl.sql.compile.SingleChildResultSetNode
acceptChildren, addNewPredicate, adjustForSortElimination, adjustForSortElimination, changeAccessPath, decrementLevel, ensurePredicateList, forUpdate, getChildResult, getFinalCostEstimate, getFromTableByName, getTrulyTheBestAccessPath, initAccessPaths, isNotExists, isOrderedOn, modifyAccessPaths, preprocess, pullOptPredicates, pushExpressions, referencesSessionSchema, referencesTarget, reflectionNeededForProjection, setChildResult, setLevel, subqueryReferencesTarget, updateBestPlanMap, updateTargetLockMode
Methods inherited from class org.apache.derby.impl.sql.compile.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, transformOuterJoins, uniqueJoin, verifyProperties
Methods inherited from class org.apache.derby.impl.sql.compile.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, 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 org.apache.derby.impl.sql.compile.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 java.lang.Object
clone, equals, finalize, 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
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Field Details
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groupingList
GroupByList groupingListThe GROUP BY list -
aggregates
The list of all aggregates in the query block that contains this group by. -
aggInfo
Information that is used at execution time to process aggregates. -
parent
FromTable parentThe parent to the GroupByNode. If we need to generate a ProjectRestrict over the group by then this is set to that node. Otherwise it is null. -
addDistinctAggregate
private boolean addDistinctAggregate -
singleInputRowOptimization
private boolean singleInputRowOptimization -
addDistinctAggregateColumnNum
private int addDistinctAggregateColumnNum -
isInSortedOrder
private final boolean isInSortedOrder -
havingClause
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havingSubquerys
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Constructor Details
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GroupByNode
GroupByNode(ResultSetNode bottomPR, GroupByList groupingList, List<AggregateNode> aggregates, ValueNode havingClause, SubqueryList havingSubquerys, int nestingLevel, ContextManager cm) throws StandardException Constructor for a GroupByNode.- Parameters:
bottomPR
- The child FromTablegroupingList
- The groupingListaggregates
- The list of aggregates from the query block. Since aggregation is done at the same time as grouping, we need them here.havingClause
- The having clause.havingSubquerys
- subqueries in the having clause.nestingLevel
- NestingLevel of this group by node. This is used for error checking of group by queries with having clause.cm
- The context manager- Throws:
StandardException
- Thrown on error
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Method Details
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getIsInSortedOrder
boolean getIsInSortedOrder()Get whether or not the source is in sorted order.- Returns:
- Whether or not the source is in sorted order.
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addAggregates
Add the extra result columns required by the aggregates to the result list. -
addDistinctAggregatesToOrderBy
private void addDistinctAggregatesToOrderBy()Add any distinct aggregates to the order by list. Asserts that there are 0 or more distincts. -
addNewPRNode
Add a new PR node for aggregation. Put the new PR under the sort. -
addUnAggColumns
In the query rewrite for group by, add the columns on which we are doing the group by.- Returns:
- havingRefsToSubstitute visitors array. Return any havingRefsToSubstitute visitors since it is too early to apply them yet; we need the AggregateNodes unmodified until after we add the new columns for aggregation (DERBY-4071).
- Throws:
StandardException
- See Also:
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addNewColumnsForAggregation
Add a whole slew of columns needed for aggregation. Basically, for each aggregate we add 3 columns: the aggregate input expression and the aggregator column and a column where the aggregate result is stored. The input expression is taken directly from the aggregator node. The aggregator is the run time aggregator. We add it to the RC list as a new object coming into the sort node.At this point this is invoked, we have the following tree:
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PR - (PARENT): RCL is the original select list
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PR - GROUP BY: RCL is empty
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PR - FROM TABLE: RCL is empty
For each ColumnReference in PR RCL
- clone the ref
- create a new RC in the bottom RCL and set it to the col ref
- create a new RC in the GROUPBY RCL and set it to point to the bottom RC
- reset the top PR ref to point to the new GROUPBY RC
aggregates
- create RC in FROM TABLE. Fill it with aggs Operator.
- create RC in FROM TABLE for agg result
- create RC in FROM TABLE for aggregator
- create RC in GROUPBY for agg input, set it to point to FROM TABLE RC
- create RC in GROUPBY for agg result
- create RC in GROUPBY for aggregator
- replace Agg with reference to RC for agg result
For a query like,
select c1, sum(c2), max(c3) from t1 group by c1;
the query tree ends up looking like this:ProjectRestrictNode RCL -> (ptr to GBN(column[0]), ptr to GBN(column[1]), ptr to GBN(column[4])) | GroupByNode RCL->(C1, SUM(C2), <agg-input>,
The RCL of the GroupByNode contains all the unagg (or grouping columns) followed by 3 RC's for each aggregate in this order: the final computed aggregate value, the aggregate input and the aggregator function., MAX(C3), <agg-input>, <aggregator>) | ProjectRestrict RCL->(C1, C2, C3) | FromBaseTable The Aggregator function puts the results in the first of the 3 RC's and the PR resultset in turn picks up the value from there.
The notation (ptr to GBN(column[0])) basically means that it is a pointer to the 0th RC in the RCL of the GroupByNode.
The addition of these unagg and agg columns to the GroupByNode and to the PRN is performed in addUnAggColumns and addAggregateColumns.
Note that that addition of the GroupByNode is done after the query is optimized (in SelectNode#modifyAccessPaths) which means a fair amount of patching up is needed to account for generated group by columns.
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addAggregateColumns
In the query rewrite involving aggregates, add the columns for aggregation.- Throws:
StandardException
- See Also:
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getParent
Return the parent node to this one, if there is one. It will return 'this' if there is no generated node above this one.- Returns:
- the parent node
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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 interfaceOptimizable
- Overrides:
optimizeIt
in classFromTable
- Parameters:
optimizer
- Optimizer to use.predList
- The predicate list to optimize againstouterCost
- 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:
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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 interfaceOptimizable
- Overrides:
estimateCost
in classFromTable
- Parameters:
predList
- The predicate list to optimize againstcd
- The conglomerate descriptor to get the cost ofouterCost
- The estimated cost of the part of the plan outer to this optimizable.optimizer
- The optimizer to use to help estimate the costrowOrdering
- 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:
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pushOptPredicate
Description copied from interface:Optimizable
Push an OptimizablePredicate down, if this node accepts it.- Specified by:
pushOptPredicate
in interfaceOptimizable
- Overrides:
pushOptPredicate
in classFromTable
- Parameters:
optimizablePredicate
- OptimizablePredicate to push down.- Returns:
- Whether or not the predicate was pushed down.
- Throws:
StandardException
- Thrown on error- See Also:
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toString
Convert this object to a String. See comments in QueryTreeNode.java for how this should be done for tree printing. -
printSubNodes
void printSubNodes(int depth) Prints the sub-nodes of this object. See QueryTreeNode.java for how tree printing is supposed to work.- Overrides:
printSubNodes
in classSingleChildResultSetNode
- Parameters:
depth
- The depth of this node in the tree
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flattenableInFromSubquery
Evaluate whether or not the subquery in a FromSubquery is flattenable. Currently, a FSqry is flattenable if all of the following are true: o Subquery is a SelectNode. o It contains no top level subqueries. (RESOLVE - we can relax this) o It does not contain a group by or having clause o It does not contain aggregates.- Overrides:
flattenableInFromSubquery
in classSingleChildResultSetNode
- Parameters:
fromList
- The outer from list- Returns:
- boolean Whether or not the FromSubquery is flattenable.
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optimize
ResultSetNode optimize(DataDictionary dataDictionary, PredicateList predicates, double outerRows) throws StandardException Optimize this GroupByNode.- Overrides:
optimize
in classSingleChildResultSetNode
- Parameters:
dataDictionary
- The DataDictionary to use for optimizationpredicates
- 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
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makeResultDescriptors
ResultColumnDescriptor[] makeResultDescriptors()- Overrides:
makeResultDescriptors
in classResultSetNode
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isOneRowResultSet
Return whether or not the underlying ResultSet tree will return a single row, at most. This is important for join nodes where we can save the extra next on the right side if we know that it will return at most 1 row.- Overrides:
isOneRowResultSet
in classSingleChildResultSetNode
- Returns:
- Whether or not the underlying ResultSet tree will return a single row.
- Throws:
StandardException
- Thrown on error
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generate
generate the sort result set operating over the source result set. Adds distinct aggregates to the sort if necessary.- Overrides:
generate
in classQueryTreeNode
- Parameters:
acb
- The ActivationClassBuilder for the class being builtmb
- The method for the generated code to go into- Throws:
StandardException
- Thrown on error
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genScalarAggregateResultSet
Generate the code to evaluate scalar aggregates. -
genGroupedAggregateResultSet
private void genGroupedAggregateResultSet(ActivationClassBuilder acb, MethodBuilder mb) throws StandardException Generate the code to evaluate grouped aggregates.- Throws:
StandardException
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getColumnReference
private ResultColumn getColumnReference(ResultColumn targetRC, DataDictionary dd) throws StandardException Method for creating a new result column referencing the one passed in.- Parameters:
targetRC
- the sourcedd
-- Returns:
- the new result column
- Throws:
StandardException
- on error
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considerPostOptimizeOptimizations
Consider any optimizations after the optimizer has chosen a plan. Optimizations include: o min optimization for scalar aggregates o max optimization for scalar aggregates- Parameters:
selectHasPredicates
- true if SELECT containing this vector/scalar aggregate has a restriction- Throws:
StandardException
- on error
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