Package edu.caltech.nanodb.functions

Class NullIf

java.lang.Object

edu.caltech.nanodb.functions.Function

edu.caltech.nanodb.functions.ScalarFunction

edu.caltech.nanodb.functions.SimpleFunction

edu.caltech.nanodb.functions.NullIf

All Implemented Interfaces:

java.lang.Cloneable

public class NullIf
extends SimpleFunction

Implements NULLIF(cond, expr). Returns NULL if the first argument is TRUE, else returns the second argument.

Author:

emil

Constructor Summary

Constructors

Constructor	Description
NullIf()

Method Summary

Modifier and Type	Method	Description
java.lang.Object	evaluate(Environment env, java.util.List<Expression> args)	Evaluates the function.
ColumnType	getReturnType(java.util.List<Expression> args, Schema schema)	Returns the column type of the resulting column after applying the function.

Methods inherited from class edu.caltech.nanodb.functions.Function

clone

Methods inherited from class java.lang.Object

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

Constructor Detail

NullIf

public NullIf()

Method Detail

getReturnType

public ColumnType getReturnType(java.util.List<Expression> args,
                                Schema schema)

Description copied from class: ScalarFunction

Returns the column type of the resulting column after applying the function. This generally depends on the column type of the inputs.

Specified by:

getReturnType in class ScalarFunction

Parameters:

args - the arguments to the function call

schema - the schema of the table

Returns:

the column type of the resulting column

evaluate

public java.lang.Object evaluate(Environment env,
                                 java.util.List<Expression> args)

Description copied from class: SimpleFunction

Evaluates the function. Should be called at runtime for every function call.

Specified by:

evaluate in class SimpleFunction

Parameters:

env - Environment, in which the arguments are evaluated

args - Arguments for this function

Returns:

The value of the function