HIVE-29773: Iceberg: Support CAST(x AS VARIANT)

iceberg/iceberg-handler/src/test/queries/positive/variant_cast.q

@@ -0,0 +1,47 @@
+set hive.explain.user=false;
+
+drop table if exists variant_cast;
+
+CREATE EXTERNAL TABLE variant_cast (
+  id INT,
+  v VARIANT
+) STORED BY ICEBERG
+TBLPROPERTIES (
+  'format-version'='3'
+);
+
+-- typed variant construction: values JSON cannot express keep their real type
+INSERT INTO variant_cast VALUES
+(1, CAST(true AS VARIANT)),
+(2, CAST(42 AS VARIANT)),
+(3, CAST(1.5BD AS VARIANT)),
+(4, CAST(unhex('DEADBEEF') AS VARIANT)),
+(5, CAST(DATE '2026-07-28' AS VARIANT)),
+(6, CAST(TIMESTAMP '2026-07-28 10:00:00' AS VARIANT)),
+(7, CAST('plain' AS VARIANT)),
+(8, CAST(array(1, 2, 3) AS VARIANT)),
+(9, CAST(NULL AS VARIANT));
+
+SELECT id, v FROM variant_cast ORDER BY id;
+
+-- binary node is rendered as base64, matching Impala/Trino
+SELECT variant_get(v, '$', 'string') FROM variant_cast WHERE id = 4;
+
+-- cast over a column expression, not a constant
+drop table if exists variant_src;
+
+CREATE TABLE variant_src (id INT, s STRING);
+
+INSERT INTO variant_src VALUES (11, 'from_col');
+
+EXPLAIN INSERT INTO variant_cast SELECT id, CAST(s AS VARIANT) FROM variant_src;
+
+INSERT INTO variant_cast SELECT id, CAST(s AS VARIANT) FROM variant_src;
+
+SELECT id, v FROM variant_cast WHERE id > 10;
+
+-- identity cast over a reader-produced variant column
+SELECT id, CAST(v AS VARIANT) FROM variant_cast WHERE id > 10;
+
+drop table variant_cast;
+drop table variant_src;

iceberg/iceberg-handler/src/test/results/positive/variant_cast.q.out

@@ -0,0 +1,203 @@
+PREHOOK: query: drop table if exists variant_cast
+PREHOOK: type: DROPTABLE
+PREHOOK: Output: database:default
+POSTHOOK: query: drop table if exists variant_cast
+POSTHOOK: type: DROPTABLE
+POSTHOOK: Output: database:default
+PREHOOK: query: CREATE EXTERNAL TABLE variant_cast (
+  id INT,
+  v VARIANT
+) STORED BY ICEBERG
+TBLPROPERTIES (
+  'format-version'='3'
+)
+PREHOOK: type: CREATETABLE
+PREHOOK: Output: database:default
+PREHOOK: Output: default@variant_cast
+POSTHOOK: query: CREATE EXTERNAL TABLE variant_cast (
+  id INT,
+  v VARIANT
+) STORED BY ICEBERG
+TBLPROPERTIES (
+  'format-version'='3'
+)
+POSTHOOK: type: CREATETABLE
+POSTHOOK: Output: database:default
+POSTHOOK: Output: default@variant_cast
+PREHOOK: query: INSERT INTO variant_cast VALUES
+(1, CAST(true AS VARIANT)),
+(2, CAST(42 AS VARIANT)),
+(3, CAST(1.5BD AS VARIANT)),
+(4, CAST(unhex('DEADBEEF') AS VARIANT)),
+(5, CAST(DATE '2026-07-28' AS VARIANT)),
+(6, CAST(TIMESTAMP '2026-07-28 10:00:00' AS VARIANT)),
+(7, CAST('plain' AS VARIANT)),
+(8, CAST(array(1, 2, 3) AS VARIANT)),
+(9, CAST(NULL AS VARIANT))
+PREHOOK: type: QUERY
+PREHOOK: Input: _dummy_database@_dummy_table
+PREHOOK: Output: default@variant_cast
+POSTHOOK: query: INSERT INTO variant_cast VALUES
+(1, CAST(true AS VARIANT)),
+(2, CAST(42 AS VARIANT)),
+(3, CAST(1.5BD AS VARIANT)),
+(4, CAST(unhex('DEADBEEF') AS VARIANT)),
+(5, CAST(DATE '2026-07-28' AS VARIANT)),
+(6, CAST(TIMESTAMP '2026-07-28 10:00:00' AS VARIANT)),
+(7, CAST('plain' AS VARIANT)),
+(8, CAST(array(1, 2, 3) AS VARIANT)),
+(9, CAST(NULL AS VARIANT))
+POSTHOOK: type: QUERY
+POSTHOOK: Input: _dummy_database@_dummy_table
+POSTHOOK: Output: default@variant_cast
+PREHOOK: query: SELECT id, v FROM variant_cast ORDER BY id
+PREHOOK: type: QUERY
+PREHOOK: Input: default@variant_cast
+PREHOOK: Output: hdfs://### HDFS PATH ###
+POSTHOOK: query: SELECT id, v FROM variant_cast ORDER BY id
+POSTHOOK: type: QUERY
+POSTHOOK: Input: default@variant_cast
+POSTHOOK: Output: hdfs://### HDFS PATH ###
+1	true
+2	42
+3	1.5
+4	"3q2+7w=="
+5	"2026-07-28"
+6	"2026-07-28 10:00:00"
+7	"plain"
+8	[1,2,3]
+9	NULL
+PREHOOK: query: SELECT variant_get(v, '$', 'string') FROM variant_cast WHERE id = 4
+PREHOOK: type: QUERY
+PREHOOK: Input: default@variant_cast
+PREHOOK: Output: hdfs://### HDFS PATH ###
+POSTHOOK: query: SELECT variant_get(v, '$', 'string') FROM variant_cast WHERE id = 4
+POSTHOOK: type: QUERY
+POSTHOOK: Input: default@variant_cast
+POSTHOOK: Output: hdfs://### HDFS PATH ###
+3q2+7w==
+PREHOOK: query: drop table if exists variant_src
+PREHOOK: type: DROPTABLE
+PREHOOK: Output: database:default
+POSTHOOK: query: drop table if exists variant_src
+POSTHOOK: type: DROPTABLE
+POSTHOOK: Output: database:default
+PREHOOK: query: CREATE TABLE variant_src (id INT, s STRING)
+PREHOOK: type: CREATETABLE
+PREHOOK: Output: database:default
+PREHOOK: Output: default@variant_src
+POSTHOOK: query: CREATE TABLE variant_src (id INT, s STRING)
+POSTHOOK: type: CREATETABLE
+POSTHOOK: Output: database:default
+POSTHOOK: Output: default@variant_src
+PREHOOK: query: INSERT INTO variant_src VALUES (11, 'from_col')
+PREHOOK: type: QUERY
+PREHOOK: Input: _dummy_database@_dummy_table
+PREHOOK: Output: default@variant_src
+POSTHOOK: query: INSERT INTO variant_src VALUES (11, 'from_col')
+POSTHOOK: type: QUERY
+POSTHOOK: Input: _dummy_database@_dummy_table
+POSTHOOK: Output: default@variant_src
+POSTHOOK: Lineage: variant_src.id SCRIPT []
+POSTHOOK: Lineage: variant_src.s SCRIPT []
+PREHOOK: query: EXPLAIN INSERT INTO variant_cast SELECT id, CAST(s AS VARIANT) FROM variant_src
+PREHOOK: type: QUERY
+PREHOOK: Input: default@variant_src
+PREHOOK: Output: default@variant_cast
+POSTHOOK: query: EXPLAIN INSERT INTO variant_cast SELECT id, CAST(s AS VARIANT) FROM variant_src
+POSTHOOK: type: QUERY
+POSTHOOK: Input: default@variant_src
+POSTHOOK: Output: default@variant_cast
+STAGE DEPENDENCIES:
+  Stage-1 is a root stage
+  Stage-2 depends on stages: Stage-1
+  Stage-0 depends on stages: Stage-2
+  Stage-3 depends on stages: Stage-0
+
+STAGE PLANS:
+  Stage: Stage-1
+    Tez
+#### A masked pattern was here ####
+      Vertices:
+        Map 1 
+            Map Operator Tree:
+                TableScan
+                  alias: variant_src
+                  Statistics: Num rows: 1 Data size: 96 Basic stats: COMPLETE Column stats: COMPLETE
+                  Select Operator
+                    expressions: id (type: int), CAST( s AS VARIANT) (type: struct<metadata:binary,value:binary>)
+                    outputColumnNames: _col0, _col1
+                    Statistics: Num rows: 1 Data size: 340 Basic stats: COMPLETE Column stats: COMPLETE
+                    File Output Operator
+                      compressed: false
+                      Statistics: Num rows: 1 Data size: 340 Basic stats: COMPLETE Column stats: COMPLETE
+                      table:
+                          input format: org.apache.iceberg.mr.hive.HiveIcebergInputFormat
+                          output format: org.apache.iceberg.mr.hive.HiveIcebergOutputFormat
+                          serde: org.apache.iceberg.mr.hive.HiveIcebergSerDe
+                          name: default.variant_cast
+            Execution mode: vectorized
+
+  Stage: Stage-2
+    Dependency Collection
+
+  Stage: Stage-0
+    Move Operator
+      tables:
+          replace: false
+          table:
+              input format: org.apache.iceberg.mr.hive.HiveIcebergInputFormat
+              output format: org.apache.iceberg.mr.hive.HiveIcebergOutputFormat
+              serde: org.apache.iceberg.mr.hive.HiveIcebergSerDe
+              name: default.variant_cast
+
+  Stage: Stage-3
+    Stats Work
+      Basic Stats Work:
+
+PREHOOK: query: INSERT INTO variant_cast SELECT id, CAST(s AS VARIANT) FROM variant_src
+PREHOOK: type: QUERY
+PREHOOK: Input: default@variant_src
+PREHOOK: Output: default@variant_cast
+POSTHOOK: query: INSERT INTO variant_cast SELECT id, CAST(s AS VARIANT) FROM variant_src
+POSTHOOK: type: QUERY
+POSTHOOK: Input: default@variant_src
+POSTHOOK: Output: default@variant_cast
+PREHOOK: query: SELECT id, v FROM variant_cast WHERE id > 10
+PREHOOK: type: QUERY
+PREHOOK: Input: default@variant_cast
+PREHOOK: Output: hdfs://### HDFS PATH ###
+POSTHOOK: query: SELECT id, v FROM variant_cast WHERE id > 10
+POSTHOOK: type: QUERY
+POSTHOOK: Input: default@variant_cast
+POSTHOOK: Output: hdfs://### HDFS PATH ###
+11	"from_col"
+PREHOOK: query: SELECT id, CAST(v AS VARIANT) FROM variant_cast WHERE id > 10
+PREHOOK: type: QUERY
+PREHOOK: Input: default@variant_cast
+PREHOOK: Output: hdfs://### HDFS PATH ###
+POSTHOOK: query: SELECT id, CAST(v AS VARIANT) FROM variant_cast WHERE id > 10
+POSTHOOK: type: QUERY
+POSTHOOK: Input: default@variant_cast
+POSTHOOK: Output: hdfs://### HDFS PATH ###
+11	"from_col"
+PREHOOK: query: drop table variant_cast
+PREHOOK: type: DROPTABLE
+PREHOOK: Input: default@variant_cast
+PREHOOK: Output: database:default
+PREHOOK: Output: default@variant_cast
+POSTHOOK: query: drop table variant_cast
+POSTHOOK: type: DROPTABLE
+POSTHOOK: Input: default@variant_cast
+POSTHOOK: Output: database:default
+POSTHOOK: Output: default@variant_cast
+PREHOOK: query: drop table variant_src
+PREHOOK: type: DROPTABLE
+PREHOOK: Input: default@variant_src
+PREHOOK: Output: database:default
+PREHOOK: Output: default@variant_src
+POSTHOOK: query: drop table variant_src
+POSTHOOK: type: DROPTABLE
+POSTHOOK: Input: default@variant_src
+POSTHOOK: Output: database:default
+POSTHOOK: Output: default@variant_src

ql/src/java/org/apache/hadoop/hive/ql/exec/FunctionRegistry.java

@@ -788,6 +788,7 @@ public final class FunctionRegistry {
     system.registerFunction("ST_Z", ST_Z.class);
 
     // Iceberg UDFs
+    system.registerGenericUDF(serdeConstants.VARIANT_TYPE_NAME, GenericUDFToVariant.class);
     system.registerGenericUDF("parse_json", GenericUDFParseJson.class);
     system.registerGenericUDF("to_json", GenericUDFToJson.class);
     system.registerGenericUDF("variant_get", GenericUDFVariantGet.class);
@@ -1637,7 +1638,7 @@ public static boolean isOpCast(GenericUDF genericUDF) {
         udfClass == GenericUDFToVarchar.class || udfClass == GenericUDFToChar.class ||
         udfClass == GenericUDFTimestamp.class || udfClass == GenericUDFToBinary.class ||
         udfClass == GenericUDFToDate.class || udfClass == GenericUDFToDecimal.class ||
-        udfClass == GenericUDFToTimestampLocalTZ.class;
+        udfClass == GenericUDFToTimestampLocalTZ.class || udfClass == GenericUDFToVariant.class;
   }
 
   /**

ql/src/java/org/apache/hadoop/hive/ql/parse/type/TypeCheckProcFactory.java

@@ -139,6 +139,8 @@ public class TypeCheckProcFactory<T> {
         serdeConstants.INTERVAL_DAY_TIME_TYPE_NAME);
     CONVERSION_FUNCTION_TEXT_MAP.put(HiveParser.TOK_DECIMAL,
         serdeConstants.DECIMAL_TYPE_NAME);
+    CONVERSION_FUNCTION_TEXT_MAP.put(HiveParser.TOK_VARIANT,
+        serdeConstants.VARIANT_TYPE_NAME);
     CONVERSION_FUNCTION_TEXT_MAP.put(HiveParser.TOK_MAP, "toMap");
     CONVERSION_FUNCTION_TEXT_MAP.put(HiveParser.TOK_LIST, "toArray");
     CONVERSION_FUNCTION_TEXT_MAP.put(HiveParser.TOK_STRUCT, "toStruct");