Package net.sf.saffron.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.

Class Summary

RexBuilder	Factory for row expressions.
RexCall	An expression formed by a call to an operator with zero or more expressions as operands.
RexCorrelVariable	Reference to the current row of a correlating relational expression.
RexFieldAccess	Access to a field of a row-expression.
RexInputRef	Variable which references a field of an input relational expression.
RexKind	Enumeration of some important types of row-expression.
RexList	List of row-expression nodes
RexLiteral	Constant value in a row-expression.
RexNode	Row expression.
RexOperator	Defines a function
RexOperatorTable	A RexOperatorTable is ...
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.
RexTest	Regression test suite for row-expressions.
RexToSqlTranslator	Translates a row-expression to a SQL parse tree.
RexUtil	Utility methods concerning row-expressions.
RexVariable	A row-expression which references a field.

Package net.sf.saffron.rex Description

Provides a language for representing row-expressions.

Revision	$Id: //open/saffron/src/net/sf/saffron/sql/package.html#1 $
Copyright	(C) Copyright 2003-2003 Disruptive Technologies, Inc.
Author	Julian Hyde

Life-cycle

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

After the relational expression has been optimized, a saffron.opt.RelImplementor 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
  • AggInternalTranslator.RexGroupVariable and AggInternalTranslator.RexAggVariable are created temporarily while an aggregate expression is being translated
• 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.

InternalTranslator translates a Java row-expression (ParseTree) into a row-expression, all within the context of a particular QueryInfo and input relational expressions (SaffronRel).

Related packages

• net.sf.saffron.sql SQL object model
• net.sf.saffron.core Core classes, including SaffronType and SaffronTypeFactory.