Package org.apache.drill.exec.physical.impl.project

Class OutputWidthExpression

java.lang.Object

org.apache.drill.exec.physical.impl.project.OutputWidthExpression

Direct Known Subclasses:

OutputWidthExpression.FixedLenExpr, OutputWidthExpression.FunctionCallExpr, OutputWidthExpression.IfElseWidthExpr, OutputWidthExpression.VarLenReadExpr

public abstract class OutputWidthExpression
extends Object

OutputWidthExpressions are used to capture the information required to calculate the width of the output produced by a variable-width expression. This is used by the ProjectMemoryManager to calculate output-widths of the expressions being projected. Expressions in Drill are represented as a tree of LogicalExpression. During the setup phase, the OutputWidthVisitor walks the tree of LogicalExpressions and reduces it to a tree of OutputWidthExpressions. In the execution phase, the OutputWidthVisitor walks the tree of OutputWidthExpressions and reduces it to a fixed output-width by using the average-sizes of incoming columns obtained from the RecordBatchSizer

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	OutputWidthExpression.FixedLenExpr	Used to represent fixed-width values used in an expression.
static class	OutputWidthExpression.FunctionCallExpr	FunctionCallExpr captures the details required to calculate the width of the output produced by a function that produces variable-width output.
static class	OutputWidthExpression.IfElseWidthExpr	IfElseWidthExpr is uded to capture an IfExpression.
static class	OutputWidthExpression.VarLenReadExpr	VarLenReadExpr captures the inputColumnName and the readExpression used to read a variable length column.

Constructor Summary

Constructors

Constructor	Description
OutputWidthExpression()

Method Summary

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

OutputWidthExpression

public OutputWidthExpression()