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scalar-functions.md

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User-Defined Functions (UDFs)

Pinot currently supports two ways of for user to implement their own functions

  • Groovy Scripts
  • Scalar Functions

Groovy Scripts

Pinot allows you the run any function other than those supported out of the box using Apache Groovy scripts. The syntax for executing groovy script within the query is as follows -

GROOVY('result value metadata json', ''groovy script', arg0, arg1, arg2...)

This function will execute the groovy script using the arguments provided and return the result which matches the provided result value metadata.** **The function requires the following arguments -

Result value metadata json - json string representing result value metadata. Must contain non-null keys resultType and isSingleValue.

Groovy script to execute- groovy script string, which uses arg0, arg1, arg2 etc to refer to the arguments provided within the script

arguments - pinot columns/other transform functions which are arguments to the groovy script

Examples

  • Add colA and colB and return a single-value INT
    groovy('{"returnType":"INT","isSingleValue":true}', 'arg0 + arg1', colA, colB)\

  • Find the max element in mvColumn array and return a single-value INT

    groovy('{"returnType":"INT","isSingleValue":true}', 'arg0.toList().max()', mvColumn)\

  • Find all elements of the array mvColumn and return as a multi-value LONG column

    groovy('{"returnType":"LONG","isSingleValue":false}', 'arg0.findIndexValues{ it > 5 }', mvColumn)\

  • Multiply length of array mvColumn with colB and return a single-value DOUBLE

    groovy('{"returnType":"DOUBLE","isSingleValue":true}', 'arg0 * arg1', arraylength(mvColumn), colB)\

  • Find all indexes in mvColumnA which have value foo, add values at those indexes in mvColumnB

    groovy( '{"returnType":"DOUBLE","isSingleValue":true}', 'def x = 0; arg0.eachWithIndex{item, idx-> if (item == "foo") {x = x + arg1[idx] }}; return x' , mvColumnA, mvColumnB)\

  • Switch case which returns a FLOAT value depending on length of mvCol array

    groovy('{\"returnType\":\"FLOAT\", \"isSingleValue\":true}', 'def result; switch(arg0.length()) { case 10: result = 1.1; break; case 20: result = 1.2; break; default: result = 1.3;}; return result.floatValue()', mvCol) \

  • Any Groovy script which takes no arguments

    groovy('new Date().format( "yyyyMMdd" )', '{"returnType":"STRING","isSingleValue":true}')

Scalar Functions

Since 0.5.0 release, Pinot supports custom functions which returns a single output for multiple inputs. Some examples of scalar functions can be found in StringFunctions and DateTimeFunctions

Pinot automatically identifies and registers all the functions with annotation @ScalarFunction

Currently only Java methods are supported.

Adding user defined scalar functions

You can add new scalar functions as follows -

  • Create a new java project. Make sure you keep the package name as org.apache.pinot.scalar.XXXX
  • In your java project include the dependency

{% tabs %} {% tab title="Maven" %}

<dependency>
  <groupId>org.apache.pinot</groupId>
  <artifactId>pinot-common</artifactId>
  <version>0.5.0</version>
 </dependency>

{% endtab %}

{% tab title="Gradle" %}

include 'org.apache.pinot:pinot-common:0.5.0'

{% endtab %} {% endtabs %}

  • Annotate your methods with @ScalarFunction annotation. Make sure the method is static and returns only a single value output. The input and output can have one of the following types -
    • Integer
    • Long
    • Double
    • String
//Example Scalar function

@ScalarFunction
static String mySubStr(String input, Integer beginIndex) {
  return input.substring(beginIndex);
}
  • Place the compiled JAR in /plugins directory in pinot. You will need to restart all pinot instances if they are already running.
  • Now, you can use the function in query as follows. Note that function name in SQL is same as function name in Java. The SQL function name is case-insensitive as well.
SELECT mysubstr(playerName, 4) FROM baseballStats