Class ColumnReference

java.lang.Object
org.apache.derby.impl.sql.compile.QueryTreeNode
org.apache.derby.impl.sql.compile.ValueNode
org.apache.derby.impl.sql.compile.ColumnReference
All Implemented Interfaces:
Visitable
public class ColumnReference extends ValueNode
A ColumnReference represents a column in the query tree. The parser generates a ColumnReference for each column reference. A column reference could be a column in a base table, a column in a view (which could expand into a complex expression), or a column in a subquery in the FROM clause.

  • Field Details

    • MERGE_UNKNOWN

      public static final int MERGE_UNKNOWN
      See Also:

    • MERGE_SOURCE

      public static final int MERGE_SOURCE
      See Also:

    • MERGE_TARGET

      public static final int MERGE_TARGET
      See Also:

    • _columnName

      private String _columnName

    • _qualifiedTableName

      private TableName _qualifiedTableName

    • tableNumber

      private int tableNumber
      The FromTable this column reference is bound to.

    • columnNumber

      private int columnNumber
      The column number in the underlying FromTable. But note source.
      See Also:

    • source

      private ResultColumn source
      This is where the value for this column reference will be coming from. Note that for join nodes, tableNumber/columnNumber will point to the column in the left or right join participant FromTable, whereas source will be bound to the RC in the result column list of the join node. See also the comment at the end of JoinNode#getMatchingColumn.
      See Also:

    • _origSource

      private ResultColumn _origSource

    • origName

      private String origName

    • _origTableNumber

      private int _origTableNumber

    • _origColumnNumber

      private int _origColumnNumber

    • tableNumberBeforeFlattening

      private int tableNumberBeforeFlattening

    • columnNumberBeforeFlattening

      private int columnNumberBeforeFlattening

    • replacesAggregate

      private boolean replacesAggregate

    • replacesWindowFunctionCall

      private boolean replacesWindowFunctionCall

    • nestingLevel

      private int nestingLevel

    • sourceLevel

      private int sourceLevel

    • scoped

      private boolean scoped

    • remaps

      private ArrayList<ColumnReference.RemapInfo> remaps

    • _mergeTableID

      private int _mergeTableID
      Columns mentioned by MERGE statements need to be associated the SOURCE or TARGET table

  • Constructor Details

    • ColumnReference

      ColumnReference(String columnName, TableName tableName, int tokBeginOffset, int tokEndOffset, ContextManager cm)
      Constructor. This one is called by the parser where we could be dealing with delimited identifiers.
      Parameters:
      columnName - The name of the column being referenced
      tableName - The qualification for the column
      tokBeginOffset - begin position of token for the column name identifier from parser.
      tokEndOffset - end position of token for the column name identifier from parser.
      cm - The context manager

    • ColumnReference

      ColumnReference(String columnName, TableName tableName, ContextManager cm)
      Constructor.
      Parameters:
      columnName - The name of the column being referenced
      tableName - The qualification for the column
      cm - The context manager

  • Method Details

    • toString

      public String toString()
      Convert this object to a String. See comments in QueryTreeNode.java for how this should be done for tree printing.
      Overrides:
      toString in class ValueNode
      Returns:
      This object as a String

    • 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 QueryTreeNode
      Parameters:
      depth - The depth of this node in the tree

    • getCorrelated

      boolean getCorrelated()
      Return whether or not this CR is correlated.
      Returns:
      Whether or not this CR is correlated.

    • setNestingLevel

      void setNestingLevel(int nestingLevel)
      Set the nesting level for this CR. (The nesting level at which the CR appears.)
      Parameters:
      nestingLevel - The Nesting level at which the CR appears.

    • getNestingLevel

      private int getNestingLevel()
      Get the nesting level for this CR.
      Returns:
      The nesting level for this CR.

    • setSourceLevel

      void setSourceLevel(int sourceLevel)
      Set the source level for this CR. (The nesting level of the source of the CR.)
      Parameters:
      sourceLevel - The Nesting level of the source of the CR.

    • getSourceLevel

      int getSourceLevel()
      Get the source level for this CR.
      Returns:
      The source level for this CR.

    • markGeneratedToReplaceAggregate

      void markGeneratedToReplaceAggregate()
      Mark this node as being generated to replace an aggregate. (Useful for replacing aggregates in the HAVING clause with column references to the matching aggregate in the user's SELECT.

    • markGeneratedToReplaceWindowFunctionCall

      void markGeneratedToReplaceWindowFunctionCall()
      Mark this node as being generated to replace a window function call.

    • getGeneratedToReplaceAggregate

      boolean getGeneratedToReplaceAggregate()
      Determine whether or not this node was generated to replace an aggregate in the user's SELECT.
      Returns:
      boolean Whether or not this node was generated to replace an aggregate in the user's SELECT.

    • getGeneratedToReplaceWindowFunctionCall

      boolean getGeneratedToReplaceWindowFunctionCall()
      Determine whether or not this node was generated to replace a window function call in the user's SELECT.
      Returns:
      boolean Whether or not this node was generated to replace a window function call in the user's SELECT.

    • getClone

      ValueNode getClone() throws StandardException
      Return a clone of this node.
      Overrides:
      getClone in class ValueNode
      Returns:
      ValueNode A clone of this node.
      Throws:
      StandardException - Thrown on error

    • copyFields

      void copyFields(ColumnReference oldCR) throws StandardException
      Copy all of the "appropriate fields" for a shallow copy.
      Parameters:
      oldCR - The ColumnReference to copy from.
      Throws:
      StandardException - Thrown on error

    • bindExpression

      ColumnReference bindExpression(FromList fromList, SubqueryList subqueryList, List<AggregateNode> aggregates) throws StandardException
      Bind this expression. This means binding the sub-expressions, as well as figuring out what the return type is for this expression. NOTE: We must explicitly check for a null FromList here, column reference without a FROM list, as the grammar allows the following: insert into t1 values(c1)
      Overrides:
      bindExpression in class ValueNode
      Parameters:
      fromList - The FROM list for the query this expression is in, for binding columns.
      subqueryList - The subquery list being built as we find SubqueryNodes
      aggregates - The aggregate list being built as we find AggregateNodes
      Returns:
      The new top of the expression tree.
      Throws:
      StandardException - Thrown on error

    • getSQLColumnName

      String getSQLColumnName()
      Get the column name for purposes of error messages or debugging. This returns the column name as used in the SQL statement. Thus if it was qualified with a table, alias name that will be included.
      Returns:
      The column name in the form [[schema.]table.]column

    • getColumnName

      public String getColumnName()
      Get the name of this column
      Overrides:
      getColumnName in class ValueNode
      Returns:
      The name of this column

    • getTableNumber

      int getTableNumber()
      Get the table number for this ColumnReference.
      Returns:
      int The table number for this ColumnReference

    • setTableNumber

      void setTableNumber(int tableNumber)
      Set this ColumnReference to refer to the given table number.
      Parameters:
      tableNumber - The table number this ColumnReference will refer to

    • getTableName

      String getTableName()
      Get the user-supplied table name of this column. This will be null if the user did not supply a name (for example, select a from t). The method will return B for this example, select b.a from t as b The method will return T for this example, select t.a from t
      Overrides:
      getTableName in class ValueNode
      Returns:
      The user-supplied name of this column. Null if no user- supplied name.

    • getSourceTableName

      String getSourceTableName()
      Get the name of the underlying(base) table this column comes from, if any. Following example queries will all return T select a from t select b.a from t as b select t.a from t
      Returns:
      The name of the base table that this column comes from. Null if not a ColumnReference.

    • getSourceSchemaName

      String getSourceSchemaName() throws StandardException
      Get the name of the schema for the Column's base table, if any. Following example queries will all return APP (assuming user is in schema APP) select t.a from t select b.a from t as b select app.t.a from t
      Returns:
      The name of the schema for Column's base table. If the column is not in a schema (i.e. is a derived column), it returns NULL.
      Throws:
      StandardException

    • updatableByCursor

      public boolean updatableByCursor()
      Is the column wirtable by the cursor or not. (ie, is it in the list of FOR UPDATE columns list)
      Overrides:
      updatableByCursor in class ValueNode
      Returns:
      TRUE, if the column is a base column of a table and is writable by cursor.

    • getQualifiedTableName

      public TableName getQualifiedTableName()
      Return the table name as the node it is.
      Returns:
      the column's table name.

    • setQualifiedTableName

      void setQualifiedTableName(TableName tableName)

    • getColumnNumber

      int getColumnNumber()
      Get the column number for this ColumnReference.
      Returns:
      int The column number for this ColumnReference

    • setColumnNumber

      void setColumnNumber(int colNum)
      Set the column number for this ColumnReference. This is used when scoping predicates for pushdown.
      Parameters:
      colNum - The new column number.

    • getSource

      ResultColumn getSource()
      Get the source this columnReference
      Returns:
      The source of this columnReference

    • setSource

      void setSource(ResultColumn source)
      Set the source this columnReference
      Parameters:
      source - The source of this columnReference

    • putAndsOnTop

      ValueNode putAndsOnTop() throws StandardException
      Do the 1st step in putting an expression into conjunctive normal form. This step ensures that the top level of the expression is a chain of AndNodes.
      Overrides:
      putAndsOnTop in class ValueNode
      Returns:
      The modified expression
      Throws:
      StandardException - Thrown on error

    • categorize

      boolean categorize(JBitSet referencedTabs, boolean simplePredsOnly)
      Categorize this predicate. Initially, this means building a bit map of the referenced tables for each predicate. If the source of this ColumnReference (at the next underlying level) is not a ColumnReference or a VirtualColumnNode then this predicate will not be pushed down. For example, in: select * from (select 1 from s) a (x) where x = 1 we will not push down x = 1. NOTE: It would be easy to handle the case of a constant, but if the inner SELECT returns an arbitrary expression, then we would have to copy that tree into the pushed predicate, and that tree could contain subqueries and method calls. Also, don't allow a predicate to be pushed down if it contains a ColumnReference that replaces an aggregate. This can happen if the aggregate is in the HAVING clause. In this case, we would be pushing the predicate into the SelectNode that evaluates the aggregate, which doesn't make sense, since the having clause is supposed to be applied to the result of the SelectNode. This also goes for column references that replaces a window function. RESOLVE - revisit this issue once we have views.
      Overrides:
      categorize in class ValueNode
      Parameters:
      referencedTabs - JBitSet with bit map of referenced FromTables
      simplePredsOnly - Whether or not to consider method calls, field references and conditional nodes when building bit map
      Returns:
      boolean Whether or not source.expression is a ColumnReference or a VirtualColumnNode or a ConstantNode.

    • remapColumnReferences

      void remapColumnReferences()
      Remap all of the ColumnReferences in this expression tree to point to the ResultColumn that is 1 level under their current source ResultColumn. This is useful for pushing down single table predicates. RESOLVE: Once we start pushing join clauses, we will need to walk the ResultColumn/VirtualColumnNode chain for them to remap the references.

    • unRemapColumnReferences

      void unRemapColumnReferences()

    • hasBeenRemapped

      protected boolean hasBeenRemapped()
      Returns true if this ColumnReference has been remapped; false otherwise.
      Returns:
      Whether or not this ColumnReference has been remapped.

    • getSourceResultColumn

      ResultColumn getSourceResultColumn()
      Description copied from class: ValueNode
      Get the source for this ValueNode.
      Overrides:
      getSourceResultColumn in class ValueNode
      Returns:
      The source of this ValueNode, null if this node is not sourced by a column.

    • remapColumnReferencesToExpressions

      ValueNode remapColumnReferencesToExpressions() throws StandardException
      Remap all ColumnReferences in this tree to be clones of the underlying expression.
      Overrides:
      remapColumnReferencesToExpressions in class ValueNode
      Returns:
      ValueNode The remapped expression tree.
      Throws:
      StandardException - Thrown on error

    • getTablesReferenced

      void getTablesReferenced(JBitSet refs)
      Update the table map to reflect the source of this CR.
      Parameters:
      refs - The table map.

    • isCloneable

      boolean isCloneable()
      Return whether or not this expression tree is cloneable.
      Overrides:
      isCloneable in class ValueNode
      Returns:
      boolean Whether or not this expression tree is cloneable.

    • constantExpression

      boolean constantExpression(PredicateList whereClause)
      Description copied from class: ValueNode
      Return whether or not this expression tree represents a constant value. In this case, "constant" means that it will always evaluate to the same thing, even if it includes columns. A column is constant if it is compared to a constant expression.
      Overrides:
      constantExpression in class ValueNode
      Returns:
      True means this expression tree represents a constant value.
      See Also:

    • generateExpression

      void generateExpression(ExpressionClassBuilder acb, MethodBuilder mb) throws StandardException
      ColumnReference's are to the current row in the system. This lets us generate a faster get that simply returns the column from the current row, rather than getting the value out and returning that, only to have the caller (in the situations needed) stuffing it back into a new column holder object. We will assume the general generate() path is for getting the value out, and use generateColumn() when we want to keep the column wrapped.
      Overrides:
      generateExpression in class ValueNode
      Parameters:
      acb - The ExpressionClassBuilder for the class being built
      mb - The method the expression will go into
      Throws:
      StandardException - Thrown on error

    • getSchemaName

      String getSchemaName()
      Get the user-supplied schema name of this column. This will be null if the user did not supply a name (for example, select t.a from t). Another example for null return value (for example, select b.a from t as b). But for following query select app.t.a from t, this will return APP Code generation of aggregate functions relies on this method
      Overrides:
      getSchemaName in class ValueNode
      Returns:
      The user-supplied schema name of this column. Null if no user- supplied name.

    • getOrderableVariantType

      protected int getOrderableVariantType()
      Return the variant type for the underlying expression. The variant type can be: VARIANT - variant within a scan (method calls and non-static field access) SCAN_INVARIANT - invariant within a scan (column references from outer tables) QUERY_INVARIANT - invariant within the life of a query (constant expressions)
      Overrides:
      getOrderableVariantType in class ValueNode
      Returns:
      The variant type for the underlying expression.

    • pointsToColumnReference

      boolean pointsToColumnReference()
      Return whether or not the source of this ColumnReference is itself a ColumnReference.
      Returns:
      Whether or not the source of this ColumnReference is itself a ColumnReference.

    • getTypeServices

      DataTypeDescriptor getTypeServices()
      The type of a ColumnReference is the type of its source unless the source is null then it is the type that has been set on this node.
      Overrides:
      getTypeServices in class ValueNode
      Returns:
      The DataTypeServices from this ValueNode. This may be null if the node isn't bound yet.

    • getSourceResultSet

      protected ResultSetNode getSourceResultSet(int[] colNum) throws StandardException
      Find the source result set for this ColumnReference and return it. Also, when the source result set is found, return the position (within the source result set's RCL) of the column referenced by this ColumnReference. The position is returned vai the colNum parameter.
      Parameters:
      colNum - Place to store the position of the column to which this ColumnReference points (position is w.r.t the source result set).
      Returns:
      The source result set for this ColumnReference; null if there is no source result set.
      Throws:
      StandardException

    • isEquivalent

      boolean isEquivalent(ValueNode o) throws StandardException
      Description copied from class: ValueNode
      Tests if this node is equivalent to the specified ValueNode. Two ValueNodes are considered equivalent if they will evaluate to the same value during query execution.

      This method provides basic expression matching facility for the derived class of ValueNode and it is used by the language layer to compare the node structural form of the two expressions for equivalence at bind phase.

      Note that it is not comparing the actual row values at runtime to produce a result; hence, when comparing SQL NULLs, they are considered to be equivalent and not unknown.

      One usage case of this method in this context is to compare the select column expression against the group by expression to check if they are equivalent. e.g.:

      SELECT c1+c2 FROM t1 GROUP BY c1+c2

      In general, node equivalence is determined by the derived class of ValueNode. But they generally abide to the rules below:

      • The two ValueNodes must be of the same node type to be considered equivalent. e.g.: CastNode vs. CastNode - equivalent (if their args also match), ColumnReference vs CastNode - not equivalent.
      • If node P contains other ValueNode(s) and so on, those node(s) must also be of the same node type to be considered equivalent.
      • If node P takes a parameter list, then the number of arguments and its arguments for the two nodes must also match to be considered equivalent. e.g.: CAST(c1 as INTEGER) vs CAST(c1 as SMALLINT), they are not equivalent.
      • When comparing SQL NULLs in this context, they are considered to be equivalent.
      • If this does not apply or it is determined that the two nodes are not equivalent then the derived class of this method should return false; otherwise, return true.
      Specified by:
      isEquivalent in class ValueNode
      Parameters:
      o - the node to compare this ValueNode against.
      Returns:
      true if the two nodes are equivalent, false otherwise.
      Throws:
      StandardException

    • markAsScoped

      protected void markAsScoped()
      Mark this column reference as "scoped", which means that it was created (as a clone of another ColumnReference) to serve as the left or right operand of a scoped predicate.

    • isScoped

      protected boolean isScoped()
      Return whether or not this ColumnReference is scoped.

    • setMergeTableID

      void setMergeTableID(int mergeTableID)
      Associate this column with a SOURCE or TARGET table of a MERGE statement

    • prettyPrintMergeTableID

      private String prettyPrintMergeTableID(int mergeTableID)

    • getMergeTableID

      int getMergeTableID()
      Get the MERGE table (SOURCE or TARGET) associated with this column

    • acceptChildren

      void acceptChildren(Visitor v) throws StandardException
      Description copied from class: QueryTreeNode
      Accept a visitor on all child nodes. All sub-classes that add fields that should be visited, should override this method and call accept(v) on all visitable fields, as well as super.acceptChildren(v) to make sure all visitable fields defined by the super-class are accepted too.
      Overrides:
      acceptChildren in class QueryTreeNode
      Parameters:
      v - the visitor
      Throws:
      StandardException - on errors raised by the visitor