org.apache.druid.math.expr

Class ExprMacroTable

java.lang.Object

org.apache.druid.math.expr.ExprMacroTable

Direct Known Subclasses:

GuiceExprMacroTable

public class ExprMacroTable
extends Object

Mechanism by which Druid expressions can define new functions for the Druid expression language. When ExprListenerImpl is creating a FunctionExpr, ExprMacroTable will first be checked to find the function by name, falling back to Parser.getFunction(String) to map to a built-in Function if none is defined in the macro table.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ExprMacroTable.BaseScalarMacroFunctionExpr Base class for multi-argument ExprMacroTable.ExprMacro function Expr
static class	ExprMacroTable.BaseScalarUnivariateMacroFunctionExpr Base class for single argument ExprMacroTable.ExprMacro function Expr
static interface	ExprMacroTable.ExprMacro
static interface	ExprMacroTable.ExprMacroFunctionExpr stub interface to allow Parser.flatten(Expr) a way to recognize macro functions that exend this

Constructor Summary

Constructors

Constructor and Description
ExprMacroTable(List<ExprMacroTable.ExprMacro> macros)

Method Summary

Modifier and Type	Method and Description
Expr	get(String functionName, List<Expr> args) Returns an expr corresponding to a function call if this table has an entry for functionName.
List<ExprMacroTable.ExprMacro>	getMacros()
static ExprMacroTable	nil()

Methods inherited from class java.lang.Object

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

Constructor Detail

ExprMacroTable

public ExprMacroTable(List<ExprMacroTable.ExprMacro> macros)

Method Detail

nil

public static ExprMacroTable nil()

getMacros

public List<ExprMacroTable.ExprMacro> getMacros()

get

@Nullable
public Expr get(String functionName,
                          List<Expr> args)

Returns an expr corresponding to a function call if this table has an entry for functionName. Otherwise, returns null.

Parameters:

functionName - function name

args - function arguments

Returns:

expr for this function call, or null