ExprMacroTable (druid-processing 28.0.1 API)

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	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 Description

ExprMacroTable(List<ExprMacroTable.ExprMacro> macros)

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	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