[feat][calcite] Decimal pushdown - fix scale.

Author: nokiaMS

core/src/main/java/org/apache/calcite/sql/type/SqlReturnTypeInferenceChain.java

@@ -17,6 +17,7 @@
 package org.apache.calcite.sql.type;
 
 import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.sql.SqlKind;
 import org.apache.calcite.sql.SqlOperatorBinding;
 
 import com.google.common.base.Preconditions;
@@ -54,6 +55,14 @@ public class SqlReturnTypeInferenceChain implements SqlReturnTypeInference {
     for (SqlReturnTypeInference rule : rules) {
       RelDataType ret = rule.inferReturnType(opBinding);
       if (ret != null) {
+        if (opBinding.getOperator().getKind() == SqlKind.DIVIDE &&
+            SqlTypeName.DECIMAL.equals(ret.getSqlTypeName())) {
+            return opBinding.getTypeFactory().
+                    createSqlType(
+                            SqlTypeName.DECIMAL,
+                            ret.getPrecision(),
+                            8);
+        }
         return ret;
       }
     }