How to get appropriate data type value from mutation in Google Spanner? about java-spanner

[nitinsridar]

Using instanceof operator? instanceof operator is used to find whether the object is an instance of the specified type. Therefore, you can check whether the value is an instance of int type. If so, you can store the value into an int variable. For example: if ( obj instanceof int ) { int myObject = obj; }

But I have to check all columns in a row and it takes lot of operation.

[codyoss]

Hey @nitinsridar I am curious to hear more about what your use case is here. Mutations are usually for modifying Spanner rows. So usually you would be putting data into them, and if so would have the Java type information. For any given key I would suspect you would know the type to cast it to, correct me if I am wrong though.

[nitinsridar]

When mutation is gone through the transaction we are publishing the mutation to pub/sub as json format, this is the use case, it's difficult to consume the mutation object at the other end so we are converting to json object and publishing to pub/sub and here I cannot convert to proper data type. Please help on this...

[olavloite]

There's no standard method in the Java client library that does this, as Mutation objects are primarily intended for sending mutations to the backend, and not for reading out or sending to other services. The best way to do what you want, would be to add a method like this to your own code, and use that to read the actual underlying value from a mutation:

  Object getUnderlyingValue(Value v) {
    switch(v.getType().getCode()) {
      case ARRAY:
        switch(v.getType().getArrayElementType().getCode()) {
          case BOOL:
            return v.getBoolArray();
          case BYTES:
            return v.getBytesArray();
          case DATE:
            return v.getDateArray();
          case FLOAT64:
            return v.getFloat64Array();
          case INT64:
            return v.getInt64Array();
          case STRING:
            return v.getStringArray();
          case TIMESTAMP:
            return v.getTimestampArray();
          case STRUCT:
            // Array of struct is not supported.
          case ARRAY:
            // Array of array is not supported.
          default:
            break;
        }
        break;
      case BOOL:
        return v.getBool();
      case BYTES:
        return v.getBytes();
      case DATE:
        return v.getDate();
      case FLOAT64:
        return v.getFloat64();
      case INT64:
        return v.getInt64();
      case STRING:
        return v.getString();
      case STRUCT:
        return v.getStruct();
      case TIMESTAMP:
        return v.getTimestamp();
      default:
        break;
    }
    throw new IllegalStateException("Value with unknown type: " + v.toString());
  }

[olavloite]

@nitinsridar Could you indicate whether the above example solves this for you? I don't think this is a very common use case, so it's not something that I think we want to add to the client library. If you add the above code snippet to your own code base, you should however be able to achieve what you wanted.

[olavloite]

Closing this as we have not heard back in a while. Please re-open if additional information is needed.