fix.

Author: gatorsmile

sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4

@@ -561,6 +561,7 @@ primaryExpression
     | CASE whenClause+ (ELSE elseExpression=expression)? END                                   #searchedCase
     | CASE value=expression whenClause+ (ELSE elseExpression=expression)? END                  #simpleCase
     | CAST '(' expression AS dataType ')'                                                      #cast
+    | STRUCT '(' (argument+=namedExpression (',' argument+=namedExpression)*)? ')'             #struct
     | FIRST '(' expression (IGNORE NULLS)? ')'                                                 #first
     | LAST '(' expression (IGNORE NULLS)? ')'                                                  #last
     | POSITION '(' substr=valueExpression IN str=valueExpression ')'                           #position

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/dsl/package.scala

@@ -168,6 +168,7 @@ package object dsl {
       case Seq() => UnresolvedStar(None)
       case target => UnresolvedStar(Option(target))
     }
+    def namedStruct(e: Expression*): Expression = CreateNamedStruct(e)
 
     def callFunction[T, U](
         func: T => U,

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala

@@ -1060,6 +1060,13 @@ class AstBuilder(conf: SQLConf) extends SqlBaseBaseVisitor[AnyRef] with Logging
     Cast(expression(ctx.expression), visitSparkDataType(ctx.dataType))
   }
 
+  /**
+   * Create a [[CreateStruct]] expression.
+   */
+  override def visitStruct(ctx: StructContext): Expression = withOrigin(ctx) {
+    CreateStruct(ctx.argument.asScala.map(expression))
+  }
+
   /**
    * Create a [[First]] expression.
    */

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ExpressionParserSuite.scala

@@ -231,7 +231,6 @@ class ExpressionParserSuite extends PlanTest {
     assertEqual("foo(distinct a, b)", 'foo.distinctFunction('a, 'b))
     assertEqual("grouping(distinct a, b)", 'grouping.distinctFunction('a, 'b))
     assertEqual("`select`(all a, b)", 'select.function('a, 'b))
-    assertEqual("foo(a as x, b as e)", 'foo.function('a as 'x, 'b as 'e))
   }
 
   test("window function expressions") {
@@ -330,7 +329,9 @@ class ExpressionParserSuite extends PlanTest {
     assertEqual("a.b", UnresolvedAttribute("a.b"))
     assertEqual("`select`.b", UnresolvedAttribute("select.b"))
     assertEqual("(a + b).b", ('a + 'b).getField("b")) // This will fail analysis.
-    assertEqual("struct(a, b).b", 'struct.function('a, 'b).getField("b"))
+    assertEqual(
+      "struct(a, b).b",
+      namedStruct(NamePlaceholder, 'a, NamePlaceholder, 'b).getField("b"))
   }
 
   test("reference") {

sql/core/src/test/resources/sql-tests/inputs/struct.sql

@@ -18,3 +18,10 @@ SELECT ID, STRUCT(ST.*,CAST(ID AS STRING) AS E) NST FROM tbl_x;
 
 -- Prepend a column to a struct
 SELECT ID, STRUCT(CAST(ID AS STRING) AS AA, ST.*) NST FROM tbl_x;
+
+-- Select a column from a struct
+SELECT ID, STRUCT(ST.*).C NST FROM tbl_x;
+SELECT ID, STRUCT(ST.C, ST.D).D NST FROM tbl_x;
+
+-- Select an alias from a struct
+SELECT ID, STRUCT(ST.C as STC, ST.D as STD).STD FROM tbl_x;

sql/core/src/test/resources/sql-tests/results/struct.sql.out

@@ -1,5 +1,5 @@
 -- Automatically generated by SQLQueryTestSuite
--- Number of queries: 6
+-- Number of queries: 9
 
 
 -- !query 0
@@ -58,3 +58,33 @@ struct<ID:int,NST:struct<AA:string,C:string,D:string>>
 1	{"AA":"1","C":"gamma","D":"delta"}
 2	{"AA":"2","C":"epsilon","D":"eta"}
 3	{"AA":"3","C":"theta","D":"iota"}
+
+
+-- !query 6
+SELECT ID, STRUCT(ST.*).C NST FROM tbl_x
+-- !query 6 schema
+struct<ID:int,NST:string>
+-- !query 6 output
+1	gamma
+2	epsilon
+3	theta
+
+
+-- !query 7
+SELECT ID, STRUCT(ST.C, ST.D).D NST FROM tbl_x
+-- !query 7 schema
+struct<ID:int,NST:string>
+-- !query 7 output
+1	delta
+2	eta
+3	iota
+
+
+-- !query 8
+SELECT ID, STRUCT(ST.C as STC, ST.D as STD).STD FROM tbl_x
+-- !query 8 schema
+struct<ID:int,named_struct(STC, ST.C AS `C` AS `STC`, STD, ST.D AS `D` AS `STD`).STD:string>
+-- !query 8 output
+1	delta
+2	eta
+3	iota