Class SingleChildResultSetNode

All Implemented Interfaces:
Optimizable, Visitable
Direct Known Subclasses:
DistinctNode, GroupByNode, HashTableNode, MaterializeResultSetNode, NormalizeResultSetNode, OrderByNode, ProjectRestrictNode, RowCountNode, ScrollInsensitiveResultSetNode, WindowResultSetNode

abstract class SingleChildResultSetNode extends FromTable
A SingleChildResultSetNode represents a result set with a single child.
  • Field Details

    • childResult

      ResultSetNode childResult
      ResultSetNode under the SingleChildResultSetNode
    • hasTrulyTheBestAccessPath

      protected boolean hasTrulyTheBestAccessPath
  • Constructor Details

  • Method Details

    • getTrulyTheBestAccessPath

      public AccessPath getTrulyTheBestAccessPath()
      Description copied from interface: Optimizable
      Get the best access path overall for this Optimizable.
      Specified by:
      getTrulyTheBestAccessPath in interface Optimizable
      Overrides:
      getTrulyTheBestAccessPath in class FromTable
      See Also:
    • getChildResult

      ResultSetNode getChildResult()
      Return the childResult from this node.
      Returns:
      ResultSetNode The childResult from this node.
    • setChildResult

      void setChildResult(ResultSetNode childResult)
      Set the childResult for this node.
      Parameters:
      childResult - The new childResult for this node.
    • 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
      Overrides:
      pullOptPredicates in class FromTable
      Parameters:
      optimizablePredicates - The list to put the pulled predicates in.
      Throws:
      StandardException - Thrown on error
      See Also:
    • 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
      Overrides:
      forUpdate in class FromTable
      See Also:
    • initAccessPaths

      public void initAccessPaths(Optimizer optimizer)
      Description copied from interface: Optimizable
      Init the access paths for this optimizable.
      Specified by:
      initAccessPaths in interface Optimizable
      Overrides:
      initAccessPaths in class FromTable
      Parameters:
      optimizer - The optimizer being used.
      See Also:
    • updateBestPlanMap

      public void updateBestPlanMap(short action, 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
      Overrides:
      updateBestPlanMap in class FromTable
      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:
    • 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 class ResultSetNode
      Parameters:
      depth - The depth of this node in the tree
    • referencesTarget

      boolean referencesTarget(String name, boolean baseTable) throws StandardException
      Search to see if a query references the specifed table name.
      Overrides:
      referencesTarget in class ResultSetNode
      Parameters:
      name - Table name (String) to search for.
      baseTable - Whether or not name is for a base table
      Returns:
      true if found, else false
      Throws:
      StandardException - Thrown on error
    • referencesSessionSchema

      public boolean referencesSessionSchema() throws StandardException
      Return true if the node references SESSION schema tables (temporary or permanent)
      Overrides:
      referencesSessionSchema in class QueryTreeNode
      Returns:
      true if references SESSION schema tables, else false
      Throws:
      StandardException - Thrown on error
    • setLevel

      void setLevel(int level)
      Set the (query block) level (0-based) for this FromTable.
      Overrides:
      setLevel in class FromTable
      Parameters:
      level - The query block level for this FromTable.
    • subqueryReferencesTarget

      boolean subqueryReferencesTarget(String name, boolean baseTable) throws StandardException
      Return whether or not this ResultSetNode contains a subquery with a reference to the specified target.
      Overrides:
      subqueryReferencesTarget in class ResultSetNode
      Parameters:
      name - The table name.
      baseTable - Whether or not the name is for a base table.
      Returns:
      boolean Whether or not a reference to the table was found.
      Throws:
      StandardException - Thrown on error
    • 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 class ResultSetNode
      Parameters:
      numTables - Number of tables in the DML Statement
      gbl - The group by list, if any
      fromList - The from list, if any
      Returns:
      The generated ProjectRestrictNode atop the original FromTable.
      Throws:
      StandardException - Thrown on error
    • 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 class ResultSetNode
      Parameters:
      predicate - The predicate to add
      Returns:
      ResultSetNode The new top of the tree.
      Throws:
      StandardException - Thrown on error
    • pushExpressions

      void pushExpressions(PredicateList predicateList) throws StandardException
      Push expressions down to the first ResultSetNode which can do expression evaluation and has the same referenced table map. RESOLVE - This means only pushing down single table expressions to DistinctNodes today. Once we have a better understanding of how the optimizer will work, we can push down join clauses.
      Overrides:
      pushExpressions in class FromTable
      Parameters:
      predicateList - The PredicateList.
      Throws:
      StandardException - Thrown on error
    • 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. 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 class ResultSetNode
      Parameters:
      fromList - The outer from list
      Returns:
      boolean Whether or not the FromSubquery is flattenable.
    • ensurePredicateList

      ResultSetNode ensurePredicateList(int numTables) throws StandardException
      Ensure that the top of the RSN tree has a PredicateList.
      Overrides:
      ensurePredicateList in class ResultSetNode
      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
    • optimize

      ResultSetNode optimize(DataDictionary dataDictionary, PredicateList predicates, double outerRows) throws StandardException
      Optimize this SingleChildResultSetNode.
      Overrides:
      optimize in class ResultSetNode
      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
    • 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 class ResultSetNode
      Returns:
      The modified query tree
      Throws:
      StandardException - Thrown on error
      See Also:
    • changeAccessPath

      ResultSetNode changeAccessPath() throws StandardException
      Description copied from class: ResultSetNode
      The optimizer's decision on the access path for a result set may require the generation of extra result sets. For example, if it chooses an index for a FromBaseTable, we need an IndexToBaseRowNode above the FromBaseTable (and the FromBaseTable has to change its column list to match the index. This method in the parent class does not generate any extra result sets. It may be overridden in child classes.
      Overrides:
      changeAccessPath in class ResultSetNode
      Returns:
      A ResultSetNode tree modified to do any extra processing for the chosen access path
      Throws:
      StandardException - Thrown on error
      See Also:
    • getFromTableByName

      FromTable getFromTableByName(String name, String schemaName, boolean exactMatch) throws StandardException
      Determine whether or not the specified name is an exposed name in the current query block.
      Overrides:
      getFromTableByName in class FromTable
      Parameters:
      name - The specified name to search for as an exposed name.
      schemaName - Schema name, if non-null.
      exactMatch - Whether or not we need an exact match on specified schema and table names or match on table id.
      Returns:
      The FromTable, if any, with the exposed name.
      Throws:
      StandardException - Thrown on error
    • decrementLevel

      void decrementLevel(int decrement)
      Decrement (query block) level (0-based) for this FromTable. This is useful when flattening a subquery.
      Overrides:
      decrementLevel in class FromTable
      Parameters:
      decrement - The amount to decrement by.
    • updateTargetLockMode

      int updateTargetLockMode()
      Get the lock mode for the target of an update statement (a delete or update). The update mode will always be row for CurrentOfNodes. It will be table if there is no where clause.
      Overrides:
      updateTargetLockMode in class ResultSetNode
      Returns:
      The lock mode
      See Also:
    • isOrderedOn

      boolean isOrderedOn(ColumnReference[] crs, boolean permuteOrdering, List<FromBaseTable> fbtHolder) throws StandardException
      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 ResultSetNode
      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.
      Throws:
      StandardException - Thrown on error
    • isOneRowResultSet

      boolean isOneRowResultSet() throws StandardException
      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 class ResultSetNode
      Returns:
      Whether or not the underlying ResultSet tree will return a single row.
      Throws:
      StandardException - Thrown on error
    • isNotExists

      boolean isNotExists()
      Return whether or not the underlying ResultSet tree is for a NOT EXISTS join.
      Overrides:
      isNotExists in class ResultSetNode
      Returns:
      Whether or not the underlying ResultSet tree is for a NOT EXISTS.
    • reflectionNeededForProjection

      protected boolean reflectionNeededForProjection()
      Determine whether we need to do reflection in order to do the projection. Reflection is only needed if there is at least 1 column which is not simply selecting the source column.
      Returns:
      Whether or not we need to do reflection in order to do the projection.
    • 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 class ResultSetNode
      See Also:
    • adjustForSortElimination

      void adjustForSortElimination(RequiredRowOrdering rowOrdering) throws StandardException
      Description copied from class: ResultSetNode
      Same goal as adjustForSortElimination above, but this version takes a RequiredRowOrdering to allow nodes to adjust based on the ORDER BY clause, if needed.
      Overrides:
      adjustForSortElimination in class ResultSetNode
      Throws:
      StandardException
      See Also:
    • getFinalCostEstimate

      CostEstimate getFinalCostEstimate() throws StandardException
      Get the final CostEstimate for this node.
      Overrides:
      getFinalCostEstimate in class FromTable
      Returns:
      The final CostEstimate for this node, which is the final cost estimate for the child node.
      Throws:
      StandardException
    • acceptChildren

      void acceptChildren(Visitor v) throws StandardException
      Accept the visitor for all visitable children of this node.
      Overrides:
      acceptChildren in class FromTable
      Parameters:
      v - the visitor
      Throws:
      StandardException - on error