[Coral-Common] Modify return type of operator "/" (#401)

coral-common/src/main/java/com/linkedin/coral/common/HiveTypeSystem.java

@@ -1,5 +1,5 @@
 /**
- * Copyright 2017-2022 LinkedIn Corporation. All rights reserved.
+ * Copyright 2017-2023 LinkedIn Corporation. All rights reserved.
  * Licensed under the BSD-2 Clause license.
  * See LICENSE in the project root for license information.
  */
@@ -9,6 +9,7 @@
 import org.apache.calcite.rel.type.RelDataTypeFactory;
 import org.apache.calcite.rel.type.RelDataTypeSystemImpl;
 import org.apache.calcite.sql.type.SqlTypeName;
+import org.apache.calcite.sql.type.SqlTypeUtil;
 
 
 // Copied from Hive source code
@@ -161,6 +162,19 @@ public boolean isSchemaCaseSensitive() {
     return false;
   }
 
+  /**
+   * This method needs to be overridden to make sure that the "/" operator returns {@link org.apache.calcite.sql.type.ReturnTypes#DOUBLE}
+   * if neither of the operands is decimal type, which is compatible with the expected data type in Hive/Spark.
+   */
+  @Override
+  public RelDataType deriveDecimalDivideType(RelDataTypeFactory typeFactory, RelDataType type1, RelDataType type2) {
+    if (SqlTypeUtil.isDecimal(type1) || SqlTypeUtil.isDecimal(type2)) {
+      return super.deriveDecimalDivideType(typeFactory, type1, type2);
+    } else {
+      return nullableType(typeFactory, SqlTypeName.DOUBLE);
+    }
+  }
+
   private RelDataType nullableType(RelDataTypeFactory typeFactory, SqlTypeName typeName) {
     return typeFactory.createTypeWithNullability(typeFactory.createSqlType(typeName), true);
   }

coral-schema/src/test/java/com/linkedin/coral/schema/avro/ViewToAvroSchemaConverterTests.java

@@ -1078,5 +1078,16 @@ public void testUnionFloatAndDoublePromoteToDouble() {
         TestUtils.loadSchema("testUnionFloatAndDoublePromoteToDouble-expected.avsc"));
   }
 
+  @Test
+  public void testDivideReturnType() {
+    String viewSql = "CREATE VIEW v AS SELECT 1/2 AS a FROM baseprimitive";
+    TestUtils.executeCreateViewQuery("default", "v", viewSql);
+
+    ViewToAvroSchemaConverter viewToAvroSchemaConverter = ViewToAvroSchemaConverter.create(hiveMetastoreClient);
+    Schema actualSchema = viewToAvroSchemaConverter.toAvroSchema("default", "v");
+
+    Assert.assertEquals(actualSchema.toString(true), TestUtils.loadSchema("testDivideReturnType-expected.avsc"));
+  }
+
   // TODO: add more unit tests
 }

coral-schema/src/test/resources/testDivideReturnType-expected.avsc

@@ -0,0 +1,10 @@
+{
+  "type" : "record",
+  "name" : "v",
+  "namespace" : "default.v",
+  "fields" : [ {
+    "name" : "a",
+    "type" : [ "null", "double" ],
+    "doc" : "Field created in view by applying operator '/' with argument(s): 1, 2"
+  } ]
+}