Class FromList

All Implemented Interfaces:
Iterable<ResultSetNode>, OptimizableList, Visitable

class FromList extends QueryTreeNodeVector<ResultSetNode> implements OptimizableList
A FromList represents the list of tables in a FROM clause in a DML statement. It extends QueryTreeNodeVector.
  • Field Details

    • properties

      Properties properties
    • fixedJoinOrder

      boolean fixedJoinOrder
    • useStatistics

      boolean useStatistics
    • referencesSessionSchema

      private boolean referencesSessionSchema
    • isTransparent

      private boolean isTransparent
    • windows

      private WindowList windows
      Window definitions used for resolving window functions not containing in-line window specifications, but referring window definitions
  • Constructor Details

    • FromList

      FromList(ContextManager cm)
      Does not change the default for join order optimization, i.e. false.
      Parameters:
      cm - context manager
    • FromList

      FromList(boolean optimizeJoinOrder, ContextManager cm)
      Constructor for a FromList
      Parameters:
      optimizeJoinOrder - true if join order optimization is to be performed
      cm - context manager
    • FromList

      FromList(boolean optimizeJoinOrder, FromTable fromTable, ContextManager cm) throws StandardException
      Constructor for a FromList
      Parameters:
      optimizeJoinOrder - true if join order optimization is to be performed
      fromTable - initialize list with this table
      cm - context manager
      Throws:
      StandardException - Thrown on error
  • Method Details

    • constructorMinion

      private void constructorMinion(boolean optimizeJoinOrder)
    • getOptimizable

      public Optimizable getOptimizable(int index)
      Description copied from interface: OptimizableList
      Return the nth Optimizable in the list.
      Specified by:
      getOptimizable in interface OptimizableList
      Parameters:
      index - "index" (0 based) into the list.
      Returns:
      Optimizable The nth Optimizables in the list.
      See Also:
    • setOptimizable

      public void setOptimizable(int index, Optimizable optimizable)
      Description copied from interface: OptimizableList
      Set the nth Optimizable to the specified Optimizable.
      Specified by:
      setOptimizable in interface OptimizableList
      Parameters:
      index - "index" (0 based) into the list.
      optimizable - New nth Optimizable.
      See Also:
    • verifyProperties

      public void verifyProperties(DataDictionary dDictionary) throws StandardException
      Description copied from interface: OptimizableList
      Verify that the Properties list with optimizer overrides, if specified, is valid
      Specified by:
      verifyProperties in interface OptimizableList
      Parameters:
      dDictionary - The DataDictionary to use.
      Throws:
      StandardException - Thrown on error
      See Also:
    • addFromTable

      final void addFromTable(FromTable fromTable) throws StandardException
      Add a table to the FROM list.
      Parameters:
      fromTable - A FromTable to add to the list
      Throws:
      StandardException - Thrown on error
    • referencesTarget

      boolean referencesTarget(String name, boolean baseTable) throws StandardException
      Search to see if a query references the specifed table name.
      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
    • 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.
      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
    • isJoinColumnForRightOuterJoin

      void isJoinColumnForRightOuterJoin(ResultColumn rc)
      Go through the list of the tables and see if the passed ResultColumn is a join column for a right outer join with USING/NATURAL clause.
      See Also:
    • bindTables

      void bindTables(DataDictionary dataDictionary, FromList fromListParam) throws StandardException
      Throws:
      StandardException
    • bindExpressions

      void bindExpressions(FromList fromListParam) throws StandardException
      Bind the expressions in this FromList. This means binding the sub-expressions, as well as figuring out what the return type is for each expression.
      Throws:
      StandardException - Thrown on error
    • bindResultColumns

      void bindResultColumns(FromList fromListParam) throws StandardException
      Bind the result columns of the ResultSetNodes in this FromList when there is no base table to bind them to. This is useful for SELECT statements, where the result columns get their types from the expressions that live under them.
      Parameters:
      fromListParam - FromList to use/append to.
      Throws:
      StandardException - Thrown on error
    • expandAll

      ResultColumnList expandAll(TableName allTableName) throws StandardException
      Expand a "*" into the appropriate ResultColumnList. If the "*" is unqualified it will expand into a list of all columns in all of the base tables in the from list at the current nesting level; otherwise it will expand into a list of all of the columns in the base table that matches the qualification. NOTE: Callers are responsible for ordering the FromList by nesting level, with tables at the deepest (current) nesting level first. We will expand the "*" into a list of all columns from all tables having the same nesting level as the first FromTable in this list. The check for nesting level exists because it's possible that this FromList includes FromTables from an outer query, which can happen if there is a "transparent" FromList above this one in the query tree. Ex: select j from onerow where exists (select 1 from somerow union select * from diffrow where onerow.j < diffrow.k) If "this" is the FromList for the right child of the UNION then it will contain both "diffrow" and "onerow", the latter of which was passed down via a transparent FromList (to allow binding of the WHERE clause). In that case the "*" should only expand the result columns of "diffrow"; it should not expand the result columns of "onerow" because that table is from an outer query. We can achieve this selective expansion by looking at nesting levels.
      Parameters:
      allTableName - The qualification on the "*" as a String.
      Returns:
      ResultColumnList representing expansion
      Throws:
      StandardException - Thrown on error
    • bindColumnReference

      ResultColumn bindColumnReference(ColumnReference columnReference) throws StandardException

      Bind a column reference to one of the tables in this FromList. The column name must be unique within the tables in the FromList. An exception is thrown if a column name is not unique. This method fills in various fields in the column reference.

      NOTE: Callers are responsible for ordering the FromList by nesting level, with tables at the deepest (current) nesting level first. We will try to match against all FromTables at a given nesting level. If no match is found at a nesting level, then we proceed to the next level. We stop walking the list when the nesting level changes and we have found a match.

      NOTE: If the ColumnReference is qualified, then we will stop the search at the first nesting level where there is a match on the exposed table name. For example,

      s (a, b, c), t (d, e, f)
                      select * from s where exists (select * from t s where s.c = a)
       

      will not find a match for s.c, which is the expected ANSI behavior.

      bindTables() must have already been called on this FromList before calling this method.

      Parameters:
      columnReference - The ColumnReference describing the column to bind
      Returns:
      ResultColumn The matching ResultColumn, or null if there is no matching column
      Throws:
      StandardException - Thrown on error
    • rejectParameters

      void rejectParameters() throws StandardException
      Check for (and reject) all ? parameters directly under the ResultColumns. This is done for SELECT statements.
      Throws:
      StandardException - Thrown if a ? parameter found directly under a ResultColumn
    • LOJ_reorderable

      boolean LOJ_reorderable(int numTables) throws StandardException
      Throws:
      StandardException
    • preprocess

      void preprocess(int numTables, GroupByList gbl, ValueNode predicateTree) throws StandardException
      Preprocess the query tree - this currently means: o Generating a referenced table map for each ResultSetNode. o Putting the WHERE and HAVING clauses in conjunctive normal form (CNF). o Converting the WHERE and HAVING clauses into PredicateLists and classifying them. o Flatten those FromSubqueries which can be flattened. o Ensuring that a ProjectRestrictNode is generated on top of every FromBaseTable and generated in place of every FromSubquery which could not be flattened. o Pushing single table predicates down to the new ProjectRestrictNodes.
      Parameters:
      numTables - The number of tables in the DML Statement
      gbl - The group by list, if any
      Throws:
      StandardException - Thrown on error
    • flattenFromTables

      void flattenFromTables(ResultColumnList rcl, PredicateList predicateList, SubqueryList sql, GroupByList gbl, ValueNode havingClause) throws StandardException
      Flatten all the FromTables that are flattenable. RESOLVE - right now we just flatten FromSubqueries. We should also flatten flattenable JoinNodes here.
      Parameters:
      rcl - The RCL from the outer query
      predicateList - The PredicateList from the outer query
      sql - The SubqueryList from the outer query
      gbl - The group by list, if any
      havingClause - The HAVING clause, if any
      Throws:
      StandardException - Thrown on error
    • pushPredicates

      void pushPredicates(PredicateList predicateList) throws StandardException
      Categorize and push the predicates that are pushable.
      Parameters:
      predicateList - The query's PredicateList
      Throws:
      StandardException - Thrown on error
    • setLevel

      void setLevel(int level)
      Set the (query block) level (0-based) for the FromTables in this FromList.
      Parameters:
      level - The query block level for this table.
    • getFromTableByResultColumn

      FromTable getFromTableByResultColumn(ResultColumn rc)
      Get the FromTable from this list which has the specified ResultColumn in its RCL.
      Parameters:
      rc - The ResultColumn match on.
      Returns:
      FromTable The matching FromTable.
    • setProperties

      void setProperties(Properties props) throws StandardException
      Set the Properties list for this FromList.
      Throws:
      StandardException - Thrown on error
    • reOrder

      public void reOrder(int[] joinOrder)
      Description copied from interface: OptimizableList
      Set the join order for this list of optimizables. The join order is represented as an array of integers - each entry in the array stands for the order of the corresponding element in the list. For example, a joinOrder of {2, 0, 1} means that the 3rd Optimizable in the list (element 2, since we are zero-based) is the first one in the join order, followed by the 1st element in the list, and finally by the 2nd element in the list. This method shuffles this OptimizableList to match the join order. Obviously, the size of the array must equal the number of elements in the array, and the values in the array must be between 0 and the number of elements in the array minus 1, and the values in the array must be unique.
      Specified by:
      reOrder in interface OptimizableList
      See Also:
    • useStatistics

      public boolean useStatistics()
      Description copied from interface: OptimizableList
      user can specify that s/he doesn't want statistics to be considered when optimizing the query.
      Specified by:
      useStatistics in interface OptimizableList
      See Also:
    • optimizeJoinOrder

      public boolean optimizeJoinOrder()
      Description copied from interface: OptimizableList
      Tell whether the join order should be optimized.
      Specified by:
      optimizeJoinOrder in interface OptimizableList
      See Also:
    • legalJoinOrder

      public boolean legalJoinOrder(int numTablesInQuery)
      Description copied from interface: OptimizableList
      Tell whether the join order is legal.
      Specified by:
      legalJoinOrder in interface OptimizableList
      See Also:
    • initAccessPaths

      public void initAccessPaths(Optimizer optimizer)
      Description copied from interface: OptimizableList
      Init the access paths for these optimizables.
      Specified by:
      initAccessPaths in interface OptimizableList
      Parameters:
      optimizer - The optimizer being used.
      See Also:
    • bindUntypedNullsToResultColumns

      void bindUntypedNullsToResultColumns(ResultColumnList bindingRCL) throws StandardException
      Bind any untyped null nodes to the types in the given ResultColumnList.
      Parameters:
      bindingRCL - The ResultColumnList with the types to bind to.
      Throws:
      StandardException - Thrown on error
    • decrementLevel

      void decrementLevel(int decrement)
      Decrement (query block) level (0-based) for all of the tables in this from list. This is useful when flattening a subquery.
      Parameters:
      decrement - The amount to decrement by.
    • returnsAtMostSingleRow

      boolean returnsAtMostSingleRow(ResultColumnList rcl, ValueNode whereClause, PredicateList wherePredicates, DataDictionary dd) throws StandardException
      This method is used for both subquery flattening and distinct elimination based on a uniqueness condition. For subquery flattening we want to make sure that the query block will return at most 1 row. For distinct elimination we want to make sure that the query block will not return any duplicates. This is true if every table in the from list is (a base table and the set of columns from the table that are in equality comparisons with expressions that do not include columns from the same table is a superset of any unique index on the table) or an EXISTS FBT. In addition, at least 1 of the tables in the list has a set of columns in equality comparisons with expressions that do not include column references from the same query block is a superset of a unique index on that table. (This ensures that the query block will onlyr return a single row.) This method is expected to be called after normalization and after the from list has been preprocessed. It can be called both before and after the predicates have been pulled from the where clause. The algorithm for this is as follows If any table in the query block is not a base table, give up. For each table in the query Ignore exists table since they can only produce one row create a matrix of tables and columns from the table (tableColMap) (this is used to keep track of the join columns and constants that can be used to figure out whether the rows from a join or in a select list are distinct based on unique indexes) create an array of columns from the table(eqOuterCol) (this is used to determine that only one row will be returned from a join) if the current table is the table for the result columns set the result columns in the eqOuterCol and tableColMap (if these columns are a superset of a unique index and all joining tables result in only one row, the results will be distinct) go through all the predicates and update tableColMap and eqOuterCol with join columns and correlation variables, parameters and constants since setting constants, correlation variables and parameters, reduces the number of columns required for uniqueness in a multi-column index, they are set for all the tables (if the table is not the result table, in this case only the column of the result table is set) join columns are just updated for the column in the row of the joining table. check if the marked columns in tableColMap are a superset of a unique index (This means that the join will only produce 1 row when joined with 1 row of another table) check that there is a least one table for which the columns in eqOuterCol(i.e. constant values) are a superset of a unique index (This quarantees that there will be only one row selected from this table). Once all tables have been evaluated, check that all the tables can be joined by unique index or will have only one row
      Parameters:
      rcl - If non-null, the RCL from the query block. If non-null for subqueries, then entry can be considered as part of an = comparison.
      whereClause - The WHERE clause to consider.
      wherePredicates - The predicates that have already been pulled from the WHERE clause.
      dd - The DataDictionary to use.
      Returns:
      Whether or not query block will return at most 1 row for a subquery, no duplicates for a distinct.
      Throws:
      StandardException - Thrown on error
    • getTableNumbers

      int[] getTableNumbers()
    • genExistsBaseTables

      void genExistsBaseTables(JBitSet referencedTableMap, FromList outerFromList, boolean isNotExists) throws StandardException
      Mark all of the FromBaseTables in the list as EXISTS FBTs. Each EBT has the same dependency list - those tables that are referenced minus the tables in the from list.
      Parameters:
      referencedTableMap - The referenced table map.
      outerFromList - FromList from outer query block
      isNotExists - Whether or not for NOT EXISTS
      Throws:
      StandardException - Thrown on error
    • tableNumberIsNotExists

      boolean tableNumberIsNotExists(int tableNumber) throws StandardException
      determine whether this table is NOT EXISTS. This routine searches for the indicated table number in the fromlist and returns TRUE if the table is present in the from list and is marked NOT EXISTS, false otherwise. A table may be present in the from list for NOT EXISTS if it is used as a correlated NOT EXISTS subquery. In such a situation, when the subquery is flattened, it is important that we remember that this is a NOT EXISTS subquery, because the join semantics are different (we're looking for rows that do NOT match, rather than rows that do). And since the join semantics are different, we cannot include this table into a transitive closure of equijoins (See DERBY-3033 for a situation where this occurs).
      Parameters:
      tableNumber - which table to check
      Returns:
      true if this table is in the from list as NOT EXISTS
      Throws:
      StandardException
    • 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.
      Returns:
      The lock mode
    • hashJoinSpecified

      boolean hashJoinSpecified()
      Return whether or not the user specified a hash join for any of the tables in this list.
      Returns:
      Whether or not the user specified a hash join for any of the tables in this list.
    • markAsTransparent

      void markAsTransparent()
      Indicate that this FromList is "transparent", which means that its FromTables should be bound to tables from an outer query. Generally this is not allowed, but there are exceptions. See SetOperatorNode.setResultToBooleanTrueNode() for more.
    • setWindows

      void setWindows(WindowList windows)
      Set windows field to the supplied value.
      Parameters:
      windows - list of window definitions associated with a SELECT.
    • getWindows

      WindowList getWindows()
      Returns:
      list of window definitions associated with a SELECT.