When I am trying to use the lookup UDF join between dimension table and realtime table, it does not work. But it works for dimension table and offline table, Is it expected? I do not see such restriction from https://docs.pinot.apache.org/users/user-guide-query/lookup-udf-join. Is there anything missing?

Getting the following exception :

{
    "errorCode": 200,
    "message": "QueryExecutionError:\norg.apache.pinot.spi.exception.BadQueryRequestException: Caught exception while initializing transform function: lookup\n\tat org.apache.pinot.core.operator.transform.function.TransformFunctionFactory.get(TransformFunctionFactory.java:207)\n\tat org.apache.pinot.core.operator.transform.TransformOperator.<init>(TransformOperator.java:56)\n\tat org.apache.pinot.core.plan.TransformPlanNode.run(TransformPlanNode.java:56)\n\tat org.apache.pinot.core.plan.SelectionPlanNode.run(SelectionPlanNode.java:83)\n\tat org.apache.pinot.core.plan.CombinePlanNode$1.callJob(CombinePlanNode.java:133)\n\tat org.apache.pinot.core.plan.CombinePlanNode$1.callJob(CombinePlanNode.java:119)\n\tat org.apache.pinot.core.util.trace.TraceCallable.call(TraceCallable.java:44)\n\tat java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)\n\tat java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)\n\tat shaded.com.google.common.util.concurrent.TrustedListenableFutureTask$TrustedFutureInterruptibleTask.runInterruptibly(TrustedListenableFutureTask.java:111)\n\tat shaded.com.google.common.util.concurrent.InterruptibleTask.run(InterruptibleTask.java:58)\n\tat shaded.com.google.common.util.concurrent.TrustedListenableFutureTask.run(TrustedListenableFutureTask.java:75)\n\tat java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)\n\tat java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)"
  },

Query:

select LOOKUP(a, b, c, d) from table_REALTIME limit 10

@User can you help us?

the exception msg is unclear. but check if both tables are stored on the same node

Yeah, it turns out the realtime and offline tables were in different tenant. Dim table was not present in the tenant where the realtime table was in.