Package org.eigenbase.rex

Provides a language for representing row-expressions.

See:
Description

Interface Summary

RexAction	A RexAction is called when a RexPattern finds a match.
RexPattern	A RexPattern represents an expression with holes in it.
RexSqlConvertlet	Converts a RexNode expression into a SqlNode expression.
RexSqlConvertletTable	Collection of RexSqlConvertlets.
RexToSqlNodeConverter	Converts expressions from RexNode to SqlNode.
RexVisitor<R>	Visitor pattern for traversing a tree of RexNode objects.

Class Summary

RexBuilder	Factory for row expressions.
RexCall	An expression formed by a call to an operator with zero or more expressions as operands.
RexCallBinding	RexCallBinding implements SqlOperatorBinding by referring to an underlying collection of RexNode operands.
RexChecker	Visitor which checks the validity of a RexNode expression.
RexCopier	Shuttle which creates a deep copy of a Rex expression.
RexCorrelVariable	Reference to the current row of a correlating relational expression.
RexDynamicParam	Dynamic parameter reference in a row-expression.
RexFieldAccess	Access to a field of a row-expression.
RexInputRef	Variable which references a field of an input relational expression.
RexLiteral	Constant value in a row-expression.
RexLocalRef	Local variable.
RexMultisetUtil	Utility class for various methods related to multisets.
RexMultisetUtil.RexCallMultisetOperatorCounter	A RexShuttle that traverse all RexNode and counts total number of RexCalls traversed and number of multiset calls traversed.
RexNode	Row expression.
RexOver	Call to an aggregate function over a window.
RexOver.Finder	Visitor which detects a RexOver inside a RexNode expression.
RexPermutationShuttle	Visitor which replaces RexLocalRef objects after the expressions in a RexProgram have been reordered.
RexPermuteInputsShuttle	Shuttle which applies a permutation to its input fields.
RexProgram	A collection of expressions which read inputs, compute output expressions, and optionally use a condition to filter rows.
RexProgram.Checker	Visitor which walks over a program and checks validity.
RexProgramBuilder	Workspace for constructing a RexProgram.
RexRangeRef	Reference to a range of columns.
RexShuttle	Passes over a row-expression, calling a handler method for each node, appropriate to the type of the node.
RexSlot	Abstract base class for RexInputRef and RexLocalRef.
RexSqlReflectiveConvertletTable	Implementation of RexSqlConvertletTable.
RexSqlStandardConvertletTable	Standard implementation of RexSqlConvertletTable.
RexToSqlNodeConverterImpl	Standard implementation of RexToSqlNodeConverter.
RexToSqlTranslator	Translates a row-expression to a SQL parse tree.
RexTransformer	Takes a tree of RexNode objects and transforms it into another in one sense equivalent tree.
RexUtil	Utility methods concerning row-expressions.
RexUtil.ExpressionNormalizer	Walks over expressions and builds a bank of common sub-expressions.
RexUtil.FieldAccessFinder	Visitor which builds a bitmap of the inputs used by an expression.
RexUtil.ForwardRefFinder	Walks over an expression and throws an exception if it finds an RexInputRef with an ordinal beyond the number of fields in the input row type, or a RexLocalRef with ordinal greater than that set using RexUtil.ForwardRefFinder.setLimit(int).
RexVariable	A row-expression which references a field.
RexVisitorImpl<R>	Default implementation of RexVisitor, which visits each node but does nothing while it's there.
RexWindow	Specification of the window of rows over which a RexOver windowed aggregate is evaluated.

Enum Summary

RexKind

Enumeration of some important types of row-expression.

Exception Summary

RexOver.OverFound
RexUtil.ExpressionNormalizer.SubExprExistsException	Thrown if there is a sub-expression.
RexUtil.ForwardRefFinder.IllegalForwardRefException

Package org.eigenbase.rex Description

Provides a language for representing row-expressions.

Revision	$Id: //open/dev/farrago/src/org/eigenbase/rex/package.html#7 $
Copyright	Copyright (C) 2005-2009 The Eigenbase Project Copyright (C) 2003-2009 SQLstream, Inc. Copyright (C) 2005-2009 LucidEra, Inc.
Author	Julian Hyde

Life-cycle

A SqlToRelConverter converts a SQL parse tree consisting of SqlNode objects into a relational expression (RelNode). Several kinds of nodes in this tree have row expressions (RexNode).

After the relational expression has been optimized, a JavaRelImplementor converts it into to a plan. If the plan is a Java parse tree, row-expressions are translated into equivalent Java expressions.

Expressions

Every row-expression has a type. (Compare with SqlNode, which is created before validation, and therefore types may not be available.)

Every node in the parse tree is a RexNode. Sub-types are:

• RexLiteral represents a boolean, numeric, string, or date constant, or the value NULL.
• RexVariable represents a leaf of the tree. It has sub-types:
  • RexCorrelVariable is a correlating variable for nested-loop joins
  • RexInputRef refers to a field of an input relational expression
  • RexCall is a call to an operator or function. By means of special operators, we can use this construct to represent virtually every non-leaf node in the tree.
  • RexRangeRef refers to a collection of contiguous fields from an input relational expression. It usually exists only during translation.

  Expressions are generally created using a RexBuilder factory. If Java expressions are to be converted, you can use a derived class, JavaRexBuilder.

  Related packages

  • org.eigenbase.sql SQL object model
  • org.eigenbase.relopt Core classes, including RelDataType and RelDataTypeFactory.