Class RowResultSetNode
- java.lang.Object
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- org.apache.derby.impl.sql.compile.QueryTreeNode
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- org.apache.derby.impl.sql.compile.ResultSetNode
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- org.apache.derby.impl.sql.compile.FromTable
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- org.apache.derby.impl.sql.compile.RowResultSetNode
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- All Implemented Interfaces:
Optimizable
,Visitable
class RowResultSetNode extends FromTable
A RowResultSetNode represents the result set for a VALUES clause.
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Nested Class Summary
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Nested classes/interfaces inherited from class org.apache.derby.impl.sql.compile.ResultSetNode
ResultSetNode.QueryExpressionClauses
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Field Summary
Fields Modifier and Type Field Description private java.util.List<AggregateNode>
aggregates
(package private) ResultSetNode.QueryExpressionClauses
qec
(package private) SubqueryList
subquerys
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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
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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
Constructors Constructor Description RowResultSetNode(ResultColumnList valuesClause, java.util.Properties tableProperties, ContextManager cm)
Constructor for a RowResultSetNode.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description (package private) ResultSetNode
addNewPredicate(Predicate predicate)
Add a new predicate to the list.(package private) void
adjustForSortElimination()
Notify the underlying result set tree that the optimizer has chosen to "eliminate" a sort.(package private) void
bindExpressions(FromList fromListParam)
Bind the expressions in this RowResultSetNode.(package private) void
bindExpressionsWithTables(FromList fromListParam)
Bind the expressions in this ResultSetNode if it has tables.(package private) ResultSetNode
bindNonVTITables(DataDictionary dataDictionary, FromList fromListParam)
Bind the non VTI tables in this ResultSetNode.(package private) void
bindTargetExpressions(FromList fromListParam)
Bind the expressions in the target list.(package private) void
bindUntypedNullsToResultColumns(ResultColumnList bindingRCL)
Bind any untyped null nodes to the types in the given ResultColumnList.private boolean
canWeCacheResults()
(package private) ResultSetNode
enhanceRCLForInsert(InsertNode target, boolean inOrder, int[] colMap)
Modify the RCL of this node to match the target of the insert.(package private) ResultSetNode
ensurePredicateList(int numTables)
Ensure that the top of the RSN tree has a PredicateList.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) boolean
flattenableInFromSubquery(FromList fromList)
Evaluate whether or not the subquery in a FromSubquery is flattenable.(package private) void
generate(ActivationClassBuilder acb, MethodBuilder mb)
The generated ResultSet will be: RowResultSet -- for the VALUES clause(package private) java.lang.String
getExposedName()
Get the exposed name for this table, which is the name that can be used to refer to it in the rest of the query.(package private) ResultColumn
getMatchingColumn(ColumnReference columnReference)
Try to find a ResultColumn in the table represented by this FromTable that matches the name in the given ColumnReference.Optimizable
modifyAccessPath(JBitSet outerTables)
Modify the access path for this Optimizable, as necessary.(package private) ResultSetNode
modifyAccessPaths()
Modify the access paths according to the decisions the optimizer made.(package private) ResultSetNode
optimize(DataDictionary dataDictionary, PredicateList predicateList, double outerRows)
Optimize this SelectNode.(package private) void
optimizeSubqueries(DataDictionary dd, double rowCount)
Optimize any subqueries that haven't been optimized any where else.(package private) ResultSetNode
preprocess(int numTables, GroupByList gbl, FromList fromList)
Put a ProjectRestrictNode on top of each FromTable in the FromList.(package private) void
printSubNodes(int depth)
Prints the sub-nodes of this object.(package private) void
pushOffsetFetchFirst(ValueNode offset, ValueNode fetchFirst, boolean hasJDBClimitClause)
Push down the offset and fetch first parameters, if any, to this node.(package private) void
pushOrderByList(OrderByList orderByList)
Push the order by list down from the cursor node into its child result set so that the optimizer has all of the information that it needs to consider sort avoidance.void
pushQueryExpressionSuffix()
Set up a new level for order by and fetch/offset clauses.boolean
referencesSessionSchema()
Return true if the node references SESSION schema tables (temporary or permanent)(package private) void
replaceOrForbidDefaults(TableDescriptor ttd, ResultColumnList tcl, boolean allowDefaults)
Replace any DEFAULTs with the associated tree for the default if allowed, or flag (when inside top level set operator nodes).(package private) boolean
returnsAtMostOneRow()
Return whether or not this ResultSet tree is guaranteed to return at most 1 row based on heuristics.(package private) void
setTableConstructorTypes(ResultColumnList typeColumns)
Set the type of each parameter in the result column list for this table constructor.(package private) java.lang.String
statementToString()
(package private) void
verifySelectStarSubquery(FromList outerFromList, int subqueryType)
Verify that a SELECT * is valid for this type of subquery.-
Methods inherited from class org.apache.derby.impl.sql.compile.FromTable
acceptChildren, assignCostEstimate, canBeOrdered, columnsAreUpdatable, considerSortAvoidancePath, convertAbsoluteToRelativeColumnPosition, cursorTargetTable, decrementLevel, feasibleJoinStrategy, fillInReferencedTableMap, flatten, forUpdate, getBaseTableName, getBestAccessPath, getBestSortAvoidancePath, getCorrelationName, getCostEstimate, getCurrentAccessPath, getFinalCostEstimate, getFromTableByName, getLevel, getMergeTableID, getName, getNumColumnsReturned, getOrigTableName, getProperties, getResultColumnsForList, getSchemaDescriptor, getSchemaDescriptor, getScratchCostEstimate, getTableDescriptor, getTableName, getTableNumber, getTrulyTheBestAccessPath, getUserSpecifiedJoinStrategy, hashKeyColumns, hasLargeObjectColumns, hasTableNumber, initAccessPaths, initialCapacity, isBaseTable, isCoveringIndex, isFlattenableJoinNode, isJoinColumnForRightOuterJoin, isMaterializable, isOneRowScan, isTargetTable, legalJoinOrder, loadFactor, LOJ_reorderable, markUpdatableByCursor, maxCapacity, memoryUsageOK, needsSpecialRCLBinding, nextAccessPath, optimizeIt, pullOptPredicates, pushExpressions, pushOptPredicate, rememberAsBest, rememberJoinStrategyAsBest, rememberSortAvoidancePath, resetJoinStrategies, setCostEstimateCost, setHashKeyColumns, setLevel, setMergeTableID, setOrigTableName, setProperties, setTableNumber, startOptimizing, supportsMultipleInstantiations, tellRowOrderingAboutConstantColumns, toString, transformOuterJoins, uniqueJoin, updateBestPlanMap, verifyProperties
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Methods inherited from class org.apache.derby.impl.sql.compile.ResultSetNode
adjustForSortElimination, assignResultSetNumber, bindResultColumns, bindResultColumns, bindVTITables, changeAccessPath, columnTypesAndLengthsMatch, considerMaterialization, generateNormalizationResultSet, generateResultSet, genProjectRestrict, genProjectRestrict, genProjectRestrictForReordering, getAllResultColumns, getCandidateFinalCostEstimate, getCostEstimate, getCursorTargetTable, getFromList, getNewCostEstimate, getOptimizer, getOptimizerImpl, getRCLForInsert, getReferencedTableMap, getResultColumns, getResultSetNumber, getScratchCostEstimate, isCursorTargetTable, isInsertSource, isNotExists, isOneRowResultSet, isOrderedOn, isPossibleDistinctScan, isStatementResultSet, isUpdatableCursor, LOJgetReferencedTables, makeResultDescription, makeResultDescriptors, markAsCursorTargetTable, markForDistinctScan, markStatementResultSet, modifyAccessPaths, notCursorTargetTable, notFlattenableJoin, numDistinctAggregates, parseDefault, performMaterialization, printQueryExpressionSuffixClauses, projectResultColumns, referencesTarget, rejectParameters, rejectXMLValues, renameGeneratedResultNames, setCandidateFinalCostEstimate, setCostEstimate, setCursorTargetTable, setInsertSource, setOptimizer, setReferencedTableMap, setResultColumns, setResultSetNumber, setResultToBooleanTrueNode, setScratchCostEstimate, subqueryReferencesTarget, updateTargetLockMode
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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
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
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Methods inherited from interface org.apache.derby.iapi.sql.compile.Optimizable
getDataDictionary, getOptimizerTracer, getReferencedTableMap, getResultSetNumber, optimizerTracingIsOn
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Methods inherited from interface org.apache.derby.iapi.sql.compile.Visitable
accept, addTag, taggedWith
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Field Detail
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subquerys
SubqueryList subquerys
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aggregates
private java.util.List<AggregateNode> aggregates
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Constructor Detail
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RowResultSetNode
RowResultSetNode(ResultColumnList valuesClause, java.util.Properties tableProperties, ContextManager cm)
Constructor for a RowResultSetNode.- Parameters:
valuesClause
- The result column list for the VALUES clause.tableProperties
- Properties list associated with the tablecm
- The context manager
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Method Detail
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statementToString
java.lang.String statementToString()
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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 classResultSetNode
- Parameters:
depth
- The depth of this node in the tree
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referencesSessionSchema
public boolean referencesSessionSchema() throws StandardException
Description copied from class:QueryTreeNode
Return true if the node references SESSION schema tables (temporary or permanent)- Overrides:
referencesSessionSchema
in classQueryTreeNode
- Returns:
- true if references SESSION schema tables, else false
- Throws:
StandardException
- Thrown on error
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enhanceRCLForInsert
ResultSetNode enhanceRCLForInsert(InsertNode target, boolean inOrder, int[] colMap) throws StandardException
Modify the RCL of this node to match the target of the insert.- Overrides:
enhanceRCLForInsert
in classResultSetNode
- Parameters:
target
- the target node for the insertinOrder
- are source cols in same order as target cols?colMap
- int array representation of correspondence between RCLs - colmap[i] = -1 -> missing in current RCL colmap[i] = j -> targetRCL(i) <-> thisRCL(j+1)- Returns:
- a node that replaces this node and whose RCL matches the target RCL. May return this node if no changes to the RCL are needed, or if the RCL is modified in-place.
- Throws:
StandardException
- Thrown on error
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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:
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)
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bindNonVTITables
ResultSetNode bindNonVTITables(DataDictionary dataDictionary, FromList fromListParam) throws StandardException
Bind the non VTI tables in this ResultSetNode. This includes getting their descriptors from the data dictionary and numbering them.- Overrides:
bindNonVTITables
in classResultSetNode
- Parameters:
dataDictionary
- The DataDictionary to use for bindingfromListParam
- FromList to use/append to.- Returns:
- ResultSetNode
- Throws:
StandardException
- Thrown on error
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bindExpressions
void bindExpressions(FromList fromListParam) throws StandardException
Bind the expressions in this RowResultSetNode. This means binding the sub-expressions, as well as figuring out what the return type is for each expression.- Overrides:
bindExpressions
in classResultSetNode
- Parameters:
fromListParam
- FromList to use/append to.- Throws:
StandardException
- Thrown on error
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bindExpressionsWithTables
void bindExpressionsWithTables(FromList fromListParam) throws StandardException
Bind the expressions in this ResultSetNode if it has tables. This means binding the sub-expressions, as well as figuring out what the return type is for each expression.- Overrides:
bindExpressionsWithTables
in classResultSetNode
- Parameters:
fromListParam
- FromList to use/append to.- Throws:
StandardException
- Thrown on error
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bindTargetExpressions
void bindTargetExpressions(FromList fromListParam) throws StandardException
Bind the expressions in the target list. This means binding the sub-expressions, as well as figuring out what the return type is for each expression. This is useful for EXISTS subqueries, where we need to validate the target list before blowing it away and replacing it with a SELECT true.- Overrides:
bindTargetExpressions
in classResultSetNode
- Throws:
StandardException
- Thrown on error
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bindUntypedNullsToResultColumns
void bindUntypedNullsToResultColumns(ResultColumnList bindingRCL) throws StandardException
Bind any untyped null nodes to the types in the given ResultColumnList.- Overrides:
bindUntypedNullsToResultColumns
in classResultSetNode
- Parameters:
bindingRCL
- The ResultColumnList with the types to bind to.- Throws:
StandardException
- Thrown on error
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getMatchingColumn
ResultColumn getMatchingColumn(ColumnReference columnReference) throws StandardException
Try to find a ResultColumn in the table represented by this FromTable that matches the name in the given ColumnReference.- Overrides:
getMatchingColumn
in classResultSetNode
- Parameters:
columnReference
- The columnReference whose name we're looking for in the given table.- Returns:
- A ResultColumn whose expression is the ColumnNode that matches the ColumnReference. Returns null if there is no match.
- Throws:
StandardException
- Thrown on error
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getExposedName
java.lang.String getExposedName() throws StandardException
Get the exposed name for this table, which is the name that can be used to refer to it in the rest of the query.- Overrides:
getExposedName
in classFromTable
- Returns:
- The exposed name of this table.
- Throws:
StandardException
- Thrown on error
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verifySelectStarSubquery
void verifySelectStarSubquery(FromList outerFromList, int subqueryType) throws StandardException
Verify that a SELECT * is valid for this type of subquery.- Overrides:
verifySelectStarSubquery
in classResultSetNode
- Parameters:
outerFromList
- The FromList from the outer query block(s)subqueryType
- The subquery type- Throws:
StandardException
- Thrown on error
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pushQueryExpressionSuffix
public void pushQueryExpressionSuffix()
Description copied from class:ResultSetNode
Set up a new level for order by and fetch/offset clauses. See Javadoc forResultSetNode.QueryExpressionClauses
. Overridden by implementors of pushOrderByNode, pushOffsetFetchFirst.- Overrides:
pushQueryExpressionSuffix
in classResultSetNode
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pushOrderByList
void pushOrderByList(OrderByList orderByList)
Push the order by list down from the cursor node into its child result set so that the optimizer has all of the information that it needs to consider sort avoidance.- Overrides:
pushOrderByList
in classResultSetNode
- Parameters:
orderByList
- The order by list
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pushOffsetFetchFirst
void pushOffsetFetchFirst(ValueNode offset, ValueNode fetchFirst, boolean hasJDBClimitClause)
Push down the offset and fetch first parameters, if any, to this node.- Overrides:
pushOffsetFetchFirst
in classResultSetNode
- Parameters:
offset
- the OFFSET, if anyfetchFirst
- the OFFSET FIRST, if anyhasJDBClimitClause
- true if the clauses were added by (and have the semantics of) a JDBC limit clause
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preprocess
ResultSetNode preprocess(int numTables, GroupByList gbl, FromList fromList) throws StandardException
Put a ProjectRestrictNode on top of each FromTable in the FromList. ColumnReferences must continue to point to the same ResultColumn, so that ResultColumn must percolate up to the new PRN. However, that ResultColumn will point to a new expression, a VirtualColumnNode, which points to the FromTable and the ResultColumn that is the source for the ColumnReference. (The new PRN will have the original of the ResultColumnList and the ResultColumns from that list. The FromTable will get shallow copies of the ResultColumnList and its ResultColumns. ResultColumn.expression will remain at the FromTable, with the PRN getting a new VirtualColumnNode for each ResultColumn.expression.) We then project out the non-referenced columns. If there are no referenced columns, then the PRN's ResultColumnList will consist of a single ResultColumn whose expression is 1.- Overrides:
preprocess
in classResultSetNode
- Parameters:
numTables
- Number of tables in the DML Statementgbl
- The group by list, if anyfromList
- The from list, if any- Returns:
- The generated ProjectRestrictNode atop the original FromTable.
- Throws:
StandardException
- Thrown on error
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ensurePredicateList
ResultSetNode ensurePredicateList(int numTables) throws StandardException
Ensure that the top of the RSN tree has a PredicateList.- Overrides:
ensurePredicateList
in classResultSetNode
- Parameters:
numTables
- The number of tables in the query.- Returns:
- ResultSetNode A RSN tree with a node which has a PredicateList on top.
- Throws:
StandardException
- Thrown on error
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addNewPredicate
ResultSetNode addNewPredicate(Predicate predicate) throws StandardException
Add a new predicate to the list. This is useful when doing subquery transformations, when we build a new predicate with the left side of the subquery operator and the subquery's result column.- Overrides:
addNewPredicate
in classResultSetNode
- Parameters:
predicate
- The predicate to add- Returns:
- ResultSetNode The new top of the tree.
- Throws:
StandardException
- Thrown on error
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flattenableInFromSubquery
boolean flattenableInFromSubquery(FromList fromList)
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 or a RowResultSetNode (not a UnionNode) 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. o There is at least one result set in the from list that is not a RowResultSetNode (the reason is to avoid having an outer SelectNode with an empty FromList.- Overrides:
flattenableInFromSubquery
in classResultSetNode
- 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 predicateList, double outerRows) throws StandardException
Optimize this SelectNode. This means choosing the best access path for each table, among other things.- Overrides:
optimize
in classResultSetNode
- Parameters:
dataDictionary
- The DataDictionary to use for optimizationpredicateList
- The predicate list to optimize againstouterRows
- The number of outer joining rows- Returns:
- ResultSetNode The top of the optimized tree
- Throws:
StandardException
- Thrown on error
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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 interfaceOptimizable
- Overrides:
modifyAccessPath
in classFromTable
- 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)
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modifyAccessPaths
ResultSetNode modifyAccessPaths() throws StandardException
Description copied from class:ResultSetNode
Modify the access paths according to the decisions the optimizer made. This can include adding project/restrict nodes, index-to-base-row nodes, etc.- Overrides:
modifyAccessPaths
in classResultSetNode
- Returns:
- The modified query tree
- Throws:
StandardException
- Thrown on error- See Also:
ResultSetNode.modifyAccessPaths()
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returnsAtMostOneRow
boolean returnsAtMostOneRow()
Return whether or not this ResultSet tree is guaranteed to return at most 1 row based on heuristics. (A RowResultSetNode and a SELECT with a non-grouped aggregate will return at most 1 row.)- Overrides:
returnsAtMostOneRow
in classResultSetNode
- Returns:
- Whether or not this ResultSet tree is guaranteed to return at most 1 row based on heuristics.
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setTableConstructorTypes
void setTableConstructorTypes(ResultColumnList typeColumns) throws StandardException
Set the type of each parameter in the result column list for this table constructor.- Overrides:
setTableConstructorTypes
in classResultSetNode
- Parameters:
typeColumns
- The ResultColumnList containing the desired result types.- Throws:
StandardException
- Thrown on error
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generate
void generate(ActivationClassBuilder acb, MethodBuilder mb) throws StandardException
The generated ResultSet will be: RowResultSet -- for the VALUES clause- 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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replaceOrForbidDefaults
void replaceOrForbidDefaults(TableDescriptor ttd, ResultColumnList tcl, boolean allowDefaults) throws StandardException
Replace any DEFAULTs with the associated tree for the default if allowed, or flag (when inside top level set operator nodes). Subqueries are checked for illegal DEFAULTs elsewhere.- Overrides:
replaceOrForbidDefaults
in classResultSetNode
- Parameters:
ttd
- The TableDescriptor for the target table.tcl
- The RCL for the target table.allowDefaults
- true if allowed- Throws:
StandardException
- Thrown on error
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optimizeSubqueries
void optimizeSubqueries(DataDictionary dd, double rowCount) throws StandardException
Optimize any subqueries that haven't been optimized any where else. This is useful for a RowResultSetNode as a derived table because it doesn't get optimized otherwise.- Overrides:
optimizeSubqueries
in classFromTable
- Throws:
StandardException
- Thrown on error
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adjustForSortElimination
void adjustForSortElimination()
Description copied from class:ResultSetNode
Notify the underlying result set tree that the optimizer has chosen to "eliminate" a sort. Sort elimination can happen as part of preprocessing (see esp. SelectNode.preprocess(...)) or it can happen if the optimizer chooses an access path that inherently returns the rows in the correct order (also known as a "sort avoidance" plan). In either case we drop the sort and rely on the underlying result set tree to return its rows in the correct order. For most types of ResultSetNodes we automatically get the rows in the correct order if the sort was eliminated. One exception to this rule, though, is the case of an IndexRowToBaseRowNode, for which we have to disable bulk fetching on the underlying base table. Otherwise the index scan could return rows out of order if the base table is updated while the scan is "in progress" (i.e. while the result set is open). In order to account for this (and potentially other, similar issues in the future) this method exists to notify the result set node that it is expected to return rows in the correct order. The result set can then take necessary action to satsify this requirement--such as disabling bulk fetch in the case of IndexRowToBaseRowNode. All of that said, any ResultSetNodes for which we could potentially eliminate sorts should override this method accordingly. So we don't ever expect to get here.- Overrides:
adjustForSortElimination
in classResultSetNode
- See Also:
ResultSetNode.adjustForSortElimination()
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canWeCacheResults
private boolean canWeCacheResults() throws StandardException
- Throws:
StandardException
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