Union Operator in Pinot

Question

I've looked into Apache Pinot's documentation and can't find any evidence of the existance of an UNION operator. I've tried doing the following in Pinot's Query Console:

select column_1
from table_1 
UNION
select column_1
from table_1

but got this error:

ProcessingException(errorCode:150, message:SQLParsingError:
java.lang.ClassCastException: class org.apache.calcite.sql.SqlBasicCall cannot be cast to class org.apache.calcite.sql.SqlSelect (org.apache.calcite.sql.SqlBasicCall and org.apache.calcite.sql.SqlSelect are in unnamed module of loader 'app')
    at org.apache.pinot.sql.parsers.CalciteSqlParser.compileSqlNodeToPinotQuery(CalciteSqlParser.java:396)
    at org.apache.pinot.controller.api.resources.PinotQueryResource.getQueryResponse(PinotQueryResource.java:185)
    at org.apache.pinot.controller.api.resources.PinotQueryResource.executeSqlQuery(PinotQueryResource.java:139)
    at org.apache.pinot.controller.api.resources.PinotQueryResource.handlePostSql(PinotQueryResource.java:103))

Does anyone know if the UNION operator exists and I'm just using it wrong? In case it doesn't exist, how can I achieve the desired result?