Interface Optimizable

All Superinterfaces:
Visitable
All Known Implementing Classes:
CurrentOfNode, DistinctNode, FromBaseTable, FromSubquery, FromTable, FromVTI, GroupByNode, HalfOuterJoinNode, HashTableNode, IndexToBaseRowNode, IntersectOrExceptNode, JoinNode, MaterializeResultSetNode, NormalizeResultSetNode, OrderByNode, ProjectRestrictNode, RowCountNode, RowResultSetNode, ScrollInsensitiveResultSetNode, SetOperatorNode, SingleChildResultSetNode, TableOperatorNode, UnionNode, WindowResultSetNode

public interface Optimizable extends Visitable
Optimizable provides services for optimizing a table in a query.
  • Method Details

    • nextAccessPath

      boolean nextAccessPath(Optimizer optimizer, OptimizablePredicateList predList, RowOrdering rowOrdering) throws StandardException
      Choose the next access path to evaluate for this 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
    • optimizeIt

      CostEstimate optimizeIt(Optimizer optimizer, OptimizablePredicateList predList, CostEstimate outerCost, RowOrdering rowOrdering) throws StandardException
      Choose the best access path for this 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
    • getCurrentAccessPath

      AccessPath getCurrentAccessPath()
      Get the current access path under consideration for this Optimizable
    • getBestAccessPath

      AccessPath getBestAccessPath()
      Get the best access path for this Optimizable.
    • getBestSortAvoidancePath

      AccessPath getBestSortAvoidancePath()
      Get the best sort-avoidance path for this Optimizable.
    • getTrulyTheBestAccessPath

      AccessPath getTrulyTheBestAccessPath()
      Get the best access path overall for this Optimizable.
    • rememberSortAvoidancePath

      void rememberSortAvoidancePath()
      Mark this optimizable so that its sort avoidance path will be considered.
    • considerSortAvoidancePath

      boolean considerSortAvoidancePath()
      Check whether this optimizable's sort avoidance path should be considered.
    • rememberJoinStrategyAsBest

      void rememberJoinStrategyAsBest(AccessPath ap)
      Remember the current join strategy as the best one so far in this join order.
    • getTableDescriptor

      TableDescriptor getTableDescriptor()
      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.
    • getReferencedTableMap

      JBitSet getReferencedTableMap()
      Get the map of referenced tables for this Optimizable.
      Returns:
      JBitSet Referenced table map.
    • pushOptPredicate

      boolean pushOptPredicate(OptimizablePredicate optimizablePredicate) throws StandardException
      Push an OptimizablePredicate down, if this node accepts it.
      Parameters:
      optimizablePredicate - OptimizablePredicate to push down.
      Returns:
      Whether or not the predicate was pushed down.
      Throws:
      StandardException - Thrown on error
    • pullOptPredicates

      void pullOptPredicates(OptimizablePredicateList optimizablePredicates) throws StandardException
      Pull all the OptimizablePredicates from this Optimizable and put them in the given OptimizablePredicateList.
      Parameters:
      optimizablePredicates - The list to put the pulled predicates in.
      Throws:
      StandardException - Thrown on error
    • modifyAccessPath

      Optimizable modifyAccessPath(JBitSet outerTables) throws StandardException
      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
      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
    • isCoveringIndex

      boolean isCoveringIndex(ConglomerateDescriptor cd) throws StandardException
      Return whether or not this is a covering index. We expect to call this during generation, after access path selection is complete.
      Parameters:
      cd - ConglomerateDesriptor for index to consider
      Returns:
      boolean Whether or not this is a covering index.
      Throws:
      StandardException - Thrown on error
    • getProperties

      Properties getProperties()
      Get the Properties list, if any, associated with this optimizable.
      Returns:
      The Properties list, if any, associated with this optimizable.
    • setProperties

      void setProperties(Properties tableProperties)
      Set the Properties list for this optimizalbe.
      Parameters:
      tableProperties - The Properties list for this optimizable.
    • verifyProperties

      void verifyProperties(DataDictionary dDictionary) throws StandardException
      Verify that the Properties list with optimizer overrides, if specified, is valid
      Parameters:
      dDictionary - The DataDictionary to use.
      Throws:
      StandardException - Thrown on error
    • getName

      String getName() throws StandardException
      Get the (exposed) name of this Optimizable
      Returns:
      The name of this Optimizable.
      Throws:
      StandardException - Thrown on error
    • getBaseTableName

      String getBaseTableName()
      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).
    • convertAbsoluteToRelativeColumnPosition

      int convertAbsoluteToRelativeColumnPosition(int absolutePosition)
      Convert an absolute to a relative 0-based column position. This is useful when generating qualifiers for partial rows from the store.
      Parameters:
      absolutePosition - The absolute 0-based column position for the column.
      Returns:
      The relative 0-based column position for the column.
    • updateBestPlanMap

      void updateBestPlanMap(short action, Object planKey) throws StandardException
      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.
      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
    • rememberAsBest

      void rememberAsBest(int planType, Optimizer optimizer) throws StandardException
      Remember the current access path as the best one (so far).
      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.
    • startOptimizing

      void startOptimizing(Optimizer optimizer, RowOrdering rowOrdering)
      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.
    • estimateCost

      CostEstimate estimateCost(OptimizablePredicateList predList, ConglomerateDescriptor cd, CostEstimate outerCost, Optimizer optimizer, RowOrdering rowOrdering) throws StandardException
      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.
      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:
    • isBaseTable

      boolean isBaseTable()
      Tell whether this Optimizable represents a base table
    • isMaterializable

      boolean isMaterializable() throws StandardException
      Tell whether this Optimizable is materializable
      Throws:
      StandardException - Thrown on error
    • supportsMultipleInstantiations

      boolean supportsMultipleInstantiations()
      Tell whether this Optimizable can be instantiated multiple times
    • hasLargeObjectColumns

      boolean hasLargeObjectColumns()
      Tell whether this Optimizable has any large object (LOB) columns.
    • getResultSetNumber

      int getResultSetNumber()
      Get this Optimizable's result set number
    • getTableNumber

      int getTableNumber()
      Get this Optimizable's table number
    • hasTableNumber

      boolean hasTableNumber()
      Return true if this Optimizable has a table number
    • forUpdate

      boolean forUpdate()
      Return true if this is the target table of an update
    • initialCapacity

      int initialCapacity()
      Return the initial capacity of the hash table, for hash join strategy
    • loadFactor

      float loadFactor()
      Return the load factor of the hash table, for hash join strategy
    • hashKeyColumns

      int[] hashKeyColumns()
      Return the hash key column numbers, for hash join strategy
    • setHashKeyColumns

      void setHashKeyColumns(int[] columnNumbers)
      Set the hash key column numbers, for hash join strategy
    • feasibleJoinStrategy

      boolean feasibleJoinStrategy(OptimizablePredicateList predList, Optimizer optimizer) throws StandardException
      Is the current proposed join strategy for this optimizable feasible given the predicate list?
      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
    • memoryUsageOK

      boolean memoryUsageOK(double rowCount, int maxMemoryPerTable) throws StandardException
      Parameters:
      rowCount -
      maxMemoryPerTable -
      Returns:
      true if the memory usage of the proposed access path is OK, false if not.
      Throws:
      StandardException - standard error policy
    • maxCapacity

      int maxCapacity(JoinStrategy joinStrategy, int maxMemoryPerTable) throws StandardException
      Return the maximum capacity of the hash table, for hash join strategy
      Parameters:
      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
    • legalJoinOrder

      boolean legalJoinOrder(JBitSet assignedTableMap)
      Can this Optimizable appear at the current location in the join order. In other words, have the Optimizable's dependencies been satisfied?
      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.
    • getDataDictionary

      DataDictionary getDataDictionary() throws StandardException
      Get the DataDictionary from this Optimizable. This is useful for code generation because we need to get the constraint name if scanning a back index so that RunTimeStatistics can display the correct info.
      Returns:
      The DataDictionary to use.
      Throws:
      StandardException - Thrown on error
    • isTargetTable

      boolean isTargetTable()
      Is the optimizable the target table of an update or delete?
      Returns:
      Whether or not the optimizable the target table of an update or delete.
    • getNumColumnsReturned

      int getNumColumnsReturned()
      Get the number of the number of columns returned by this Optimizable.
      Returns:
      The number of the number of columns returned by this Optimizable.
    • isOneRowScan

      boolean isOneRowScan() throws StandardException
      Will the optimizable return at most 1 row per scan?
      Returns:
      Whether or not the optimizable will return at most 1 row per scan?
      Throws:
      StandardException - Thrown on error
    • initAccessPaths

      void initAccessPaths(Optimizer optimizer)
      Init the access paths for this optimizable.
      Parameters:
      optimizer - The optimizer being used.
    • uniqueJoin

      double uniqueJoin(OptimizablePredicateList predList) throws StandardException
      Does this optimizable have a uniqueness condition on the given predicate list, and if so, how many unique keys will be returned per scan.
      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
    • getOptimizerTracer

      OptTrace getOptimizerTracer()
      Get the optimizer tracer, if any
    • optimizerTracingIsOn

      boolean optimizerTracingIsOn()
      Report whether optimizer tracing is on