DRILL-7092: Rename map to struct in schema definition

1. Renamed map to struct in schema parser.
2. Updated sqlTypeOf function to return STRUCT instead of MAP, drillTypeOf function will return MAP as before until internal renaming is done.
3. Add is_struct alias to already existing is_map function. Function should be revisited once Drill supports true maps.
4. Updated unit tests.

closes #1688

common/src/main/java/org/apache/drill/common/types/Types.java

@@ -185,7 +185,7 @@ public static String getBaseSqlTypeName(final MajorType type) {
       // Composite types and other types that are not atomic types (SQL standard
       // or not) except ARRAY types (handled above):
 
-      case MAP:             return "MAP";
+      case MAP:             return "STRUCT"; // Drill map represents struct and in future will be renamed
       case LATE:            return "ANY";
       case NULL:            return "NULL";
       case UNION:           return "UNION";
@@ -267,7 +267,7 @@ public static int getJdbcTypeCode(final String sqlTypeName) {
       case "INTERVAL":                      return java.sql.Types.OTHER;  // JDBC (4.1) has nothing for INTERVAL
       case "INTERVAL YEAR TO MONTH":        return java.sql.Types.OTHER;
       case "INTERVAL DAY TO SECOND":        return java.sql.Types.OTHER;
-      case "MAP":                           return java.sql.Types.OTHER; // Drill doesn't support java.sql.Struct
+      case "STRUCT":                        return java.sql.Types.OTHER; // Drill doesn't support java.sql.Struct
       case "NATIONAL CHARACTER VARYING":    return java.sql.Types.NVARCHAR;
       case "NATIONAL CHARACTER":            return java.sql.Types.NCHAR;
       case "NULL":                          return java.sql.Types.NULL;

exec/java-exec/src/main/antlr4/org/apache/drill/exec/record/metadata/schema/parser/SchemaLexer.g4

@@ -55,6 +55,7 @@ MINUTE: 'MINUTE';
 SECOND: 'SECOND';
 
 MAP: 'MAP';
+STRUCT: 'STRUCT';
 ARRAY: 'ARRAY';
 
 // symbols

exec/java-exec/src/main/antlr4/org/apache/drill/exec/record/metadata/schema/parser/SchemaParser.g4

@@ -31,13 +31,13 @@ columns: column_def  (COMMA column_def)*;
 
 column_def: column property_values?;
 
-column: (primitive_column | map_column | simple_array_column | complex_array_column);
+column: (primitive_column | struct_column | simple_array_column | complex_array_column);
 
 primitive_column: column_id simple_type nullability? format_value? default_value?;
 
 simple_array_column: column_id simple_array_type nullability?;
 
-map_column: column_id map_type nullability?;
+struct_column: column_id struct_type nullability?;
 
 complex_array_column: column_id complex_array_type nullability?;
 
@@ -65,11 +65,11 @@ simple_type
 
 complex_type: (simple_array_type | complex_array_type);
 
-simple_array_type: ARRAY LEFT_ANGLE_BRACKET (simple_type | map_type) RIGHT_ANGLE_BRACKET;
+simple_array_type: ARRAY LEFT_ANGLE_BRACKET (simple_type | struct_type) RIGHT_ANGLE_BRACKET;
 
 complex_array_type: ARRAY LEFT_ANGLE_BRACKET complex_type RIGHT_ANGLE_BRACKET;
 
-map_type: MAP LEFT_ANGLE_BRACKET columns RIGHT_ANGLE_BRACKET;
+struct_type: STRUCT LEFT_ANGLE_BRACKET columns RIGHT_ANGLE_BRACKET;
 
 nullability: NOT NULL;
 

exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/UnionFunctions.java

@@ -330,7 +330,7 @@ public void eval() {
   }
 
   @SuppressWarnings("unused")
-  @FunctionTemplate(name = "IS_MAP", scope = FunctionTemplate.FunctionScope.SIMPLE, nulls=NullHandling.INTERNAL)
+  @FunctionTemplate(names = {"IS_MAP", "IS_STRUCT"}, scope = FunctionTemplate.FunctionScope.SIMPLE, nulls=NullHandling.INTERNAL)
   public static class UnionIsMap implements DrillSimpleFunc {
 
     @Param UnionHolder in;

exec/java-exec/src/main/java/org/apache/drill/exec/record/metadata/schema/parser/SchemaVisitor.java

@@ -110,10 +110,10 @@ public ColumnMetadata visitSimple_array_column(SchemaParser.Simple_array_columnC
     }
 
     @Override
-    public ColumnMetadata visitMap_column(SchemaParser.Map_columnContext ctx) {
+    public ColumnMetadata visitStruct_column(SchemaParser.Struct_columnContext ctx) {
       String name = ctx.column_id().accept(new IdVisitor());
-      // Drill does not distinguish between nullable and not null map, by default they are not null
-      return ctx.map_type().accept(new TypeVisitor(name, TypeProtos.DataMode.REQUIRED));
+      // Drill does not distinguish between nullable and not null structs, by default they are not null
+      return ctx.struct_type().accept(new TypeVisitor(name, TypeProtos.DataMode.REQUIRED));
     }
 
     @Override
@@ -277,7 +277,9 @@ public ColumnMetadata visitInterval(SchemaParser.IntervalContext ctx) {
     }
 
     @Override
-    public ColumnMetadata visitMap_type(SchemaParser.Map_typeContext ctx) {
+    public ColumnMetadata visitStruct_type(SchemaParser.Struct_typeContext ctx) {
+      // internally Drill refers to structs as maps and currently does not have true map notion
+      // Drill maps will be renamed to structs in future
       MapBuilder builder = new MapBuilder(null, name, mode);
       ColumnDefVisitor visitor = new ColumnDefVisitor();
       ctx.columns().column_def().forEach(
@@ -308,7 +310,7 @@ private static class ArrayTypeVisitor extends SchemaParserBaseVisitor<ColumnMeta
     @Override
     public ColumnMetadata visitSimple_array_type(SchemaParser.Simple_array_typeContext ctx) {
       TypeVisitor visitor = new TypeVisitor(name, TypeProtos.DataMode.REPEATED);
-      return ctx.map_type() == null ? ctx.simple_type().accept(visitor) : ctx.map_type().accept(visitor);
+      return ctx.struct_type() == null ? ctx.simple_type().accept(visitor) : ctx.struct_type().accept(visitor);
     }
 
     @Override

exec/java-exec/src/test/java/org/apache/drill/exec/record/metadata/schema/parser/TestParserErrorHandling.java

@@ -104,15 +104,15 @@ public void testMissingAngleBracket() {
 
   @Test
   public void testUnclosedAngleBracket() {
-    String schema = "col map<m array<int> not null";
+    String schema = "col struct<m array<int> not null";
     thrown.expect(SchemaParsingException.class);
     thrown.expectMessage("missing '>' at '<EOF>'");
     SchemaExprParser.parseSchema(schema);
   }
 
   @Test
-  public void testMissingColumnNameForMap() {
-    String schema = "col map<int> not null";
+  public void testMissingColumnNameForStruct() {
+    String schema = "col struct<int> not null";
     thrown.expect(SchemaParsingException.class);
     thrown.expectMessage("mismatched input 'int' expecting {ID, QUOTED_ID}");
     SchemaExprParser.parseSchema(schema);

exec/java-exec/src/test/java/org/apache/drill/exec/record/metadata/schema/parser/TestSchemaParser.java

@@ -178,11 +178,11 @@ public void testArray() {
       .addRepeatedList("nested_array")
         .addArray(TypeProtos.MinorType.INT)
       .resumeSchema()
-      .addMapArray("map_array")
+      .addMapArray("struct_array")
         .addNullable("m1", TypeProtos.MinorType.INT)
         .addNullable("m2", TypeProtos.MinorType.VARCHAR)
       .resumeSchema()
-      .addRepeatedList("nested_array_map")
+      .addRepeatedList("nested_array_struct")
         .addMapArray()
           .addNullable("nm1", TypeProtos.MinorType.INT)
           .addNullable("nm2", TypeProtos.MinorType.VARCHAR)
@@ -192,26 +192,26 @@ public void testArray() {
 
     checkSchema("simple_array array<int>"
         + ", nested_array array<array<int>>"
-        + ", map_array array<map<m1 int, m2 varchar>>"
-        + ", nested_array_map array<array<map<nm1 int, nm2 varchar>>>",
+        + ", struct_array array<struct<m1 int, m2 varchar>>"
+        + ", nested_array_struct array<array<struct<nm1 int, nm2 varchar>>>",
       schema);
 
   }
 
   @Test
-  public void testMap() {
+  public void testStruct() {
     TupleMetadata schema = new SchemaBuilder()
-      .addMap("map_col")
+      .addMap("struct_col")
         .addNullable("int_col", TypeProtos.MinorType.INT)
         .addArray("array_col", TypeProtos.MinorType.INT)
-        .addMap("nested_map")
+        .addMap("nested_struct")
           .addNullable("m1", TypeProtos.MinorType.INT)
           .addNullable("m2", TypeProtos.MinorType.VARCHAR)
         .resumeMap()
       .resumeSchema()
       .buildSchema();
 
-    checkSchema("map_col map<int_col int, array_col array<int>, nested_map map<m1 int, m2 varchar>>", schema);
+    checkSchema("struct_col struct<int_col int, array_col array<int>, nested_struct struct<m1 int, m2 varchar>>", schema);
   }
 
   @Test
@@ -222,8 +222,8 @@ public void testModeForSimpleType() {
   }
 
   @Test
-  public void testModeForMapType() {
-    TupleMetadata schema  = SchemaExprParser.parseSchema("m map<m1 int not null, m2 varchar>");
+  public void testModeForStructType() {
+    TupleMetadata schema  = SchemaExprParser.parseSchema("m struct<m1 int not null, m2 varchar>");
     ColumnMetadata map = schema.metadata("m");
     assertTrue(map.isMap());
     assertEquals(TypeProtos.DataMode.REQUIRED, map.mode());
@@ -236,7 +236,7 @@ public void testModeForMapType() {
   @Test
   public void testModeForRepeatedType() {
     TupleMetadata schema = SchemaExprParser.parseSchema(
-      "a array<int>, aa array<array<int>>, ma array<map<m1 int not null, m2 varchar>>");
+      "a array<int>, aa array<array<int>>, ma array<struct<m1 int not null, m2 varchar>>");
 
     assertTrue(schema.metadata("a").isArray());