Package edu.caltech.nanodb.functions

Class Function

java.lang.Object

edu.caltech.nanodb.functions.Function

All Implemented Interfaces:

java.lang.Cloneable

Direct Known Subclasses:

ScalarFunction, TableFunction

public abstract class Function
extends java.lang.Object
implements java.lang.Cloneable

This is the root class of all kinds of functions in NanoDB. The class hierarchy for functions is somewhat complicated; these are the important details:

• ScalarFunction is the parent class for any kind of function that returns a scalar value
  • SimpleFunction is the parent class for functions that take zero or more arguments, and compute and return a result
  • AggregateFunction is the parent class for functions that consume a (potentially large) collection of input values and compute a single aggregated value from the collection
• TableFunction is the parent class for table-returning functions

Functions must support cloning because the implementation classes often carry their own internal state values, and clearly the same function being invoked in two different parts of the same query, or being invoked concurrently by two different queries, shouldn't have a single shared set of state values. So, the simple thing to do is to just clone functions when they are retrieved from the FunctionDirectory.

Constructor Summary

Constructors

Constructor	Description
Function()

Method Summary

Modifier and Type	Method	Description
java.lang.Object	clone()	Creates a copy of expression.

Methods inherited from class java.lang.Object

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

Constructor Detail

Function

public Function()

Method Detail

clone

public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException

Creates a copy of expression.

Overrides:

clone in class java.lang.Object

Throws:

java.lang.CloneNotSupportedException