Avoid type coercion when a dereferenced field is same type

trinodb · Aug 6, 2020 · 039d3a6 · 039d3a6
1 parent 8131d34
commit 039d3a6
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Showing 2 changed files with 19 additions and 1 deletion.
diff --git a/presto-hive/src/main/java/io/prestosql/plugin/hive/HivePageSource.java b/presto-hive/src/main/java/io/prestosql/plugin/hive/HivePageSource.java
@@ -163,7 +163,12 @@ public HivePageSource(
                         .orElse(ImmutableList.of());
                 HiveType fromType = columnMapping.getBaseTypeCoercionFrom().get().getHiveTypeForDereferences(dereferenceIndices).get();
                 HiveType toType = columnMapping.getHiveColumnHandle().getHiveType();
-                coercers.add(Optional.of(createCoercer(typeManager, fromType, toType)));
+                if (!fromType.equals(toType)) {
+                    coercers.add(Optional.of(createCoercer(typeManager, fromType, toType)));
+                }
+                else {
+                    coercers.add(Optional.empty());
+                }
             }
             else {
                 coercers.add(Optional.empty());

diff --git a/presto-hive/src/test/java/io/prestosql/plugin/hive/TestHiveIntegrationSmokeTest.java b/presto-hive/src/test/java/io/prestosql/plugin/hive/TestHiveIntegrationSmokeTest.java
@@ -4336,6 +4336,19 @@ private void schemaMismatchesWithDereferenceProjections(HiveStorageFormat format
         finally {
             assertUpdate("DROP TABLE IF EXISTS evolve_test");
         }
+
+        // Verify field access when the row evolves without changes to field type
+        try {
+            assertUpdate("CREATE TABLE evolve_test (dummy bigint, a row(b bigint, c varchar), d bigint) with (format = '" + format + "', partitioned_by=array['d'])");
+            assertUpdate("INSERT INTO evolve_test values (1, row(1, 'abc'), 1)", 1);
+            assertUpdate("ALTER TABLE evolve_test DROP COLUMN a");
+            assertUpdate("ALTER TABLE evolve_test ADD COLUMN a row(b bigint, c varchar, e int)");
+            assertUpdate("INSERT INTO evolve_test values (2, row(2, 'def', 2), 2)", 1);
+            assertQuery("SELECT a.b FROM evolve_test", "VALUES 1, 2");
+        }
+        finally {
+            assertUpdate("DROP TABLE IF EXISTS evolve_test");
+        }
     }
 
     @Test