multi-value string column support for expressions

LICENSE

@@ -257,6 +257,8 @@ SOURCE/JAVA-CORE
       * core/src/main/java/org/apache/druid/java/util/common/parsers/DelimitedParser.java
       DirectExecutorService class:
       * core/src/main/java/org/apache/druid/java/util/common/concurrent/DirectExecutorService.java
+      CartesianList class:
+      * core/src/main/java/org/apache/druid/math/expr/CartesianList.java
 
     This product contains modified versions of the Dockerfile, scripts, and related configuration files
      used for building SequenceIQ's Hadoop Docker image, copyright SequenceIQ, Inc. (https://github.com/sequenceiq/hadoop-docker/)

core/src/main/antlr4/org/apache/druid/math/expr/antlr/Expr.g4

@@ -23,13 +23,21 @@ expr : 'null'                                         # null
      | expr ('<'|'<='|'>'|'>='|'=='|'!=') expr        # logicalOpExpr
      | expr ('&&'|'||') expr                          # logicalAndOrExpr
      | '(' expr ')'                                   # nestedExpr
+     | IDENTIFIER '(' lambda ',' fnArgs ')'           # applyFunctionExpr
      | IDENTIFIER '(' fnArgs? ')'                     # functionExpr
      | IDENTIFIER                                     # identifierExpr
      | DOUBLE                                         # doubleExpr
      | LONG                                           # longExpr
      | STRING                                         # string
+     | '[' DOUBLE  (',' DOUBLE)* ']'                  # doubleArray
+     | '[' LONG (',' LONG)* ']'                       # longArray
+     | '[' STRING (',' STRING)* ']'                   # stringArray
+     | '[]'                                           # emptyArray
      ;
 
+lambda : (IDENTIFIER | '(' ')' | '(' IDENTIFIER (',' IDENTIFIER)* ')') '->' expr
+       ;
+
 fnArgs : expr (',' expr)*                             # functionArgs
        ;