How to search a non-primary attribute from DynamoDB with Spring Reactive (Webflux)? - spring-webflux

Question

Suppose I have user table with fields userId, userName, password and some other fields where userId is the partition key. How could I write a query to find something from userName and not from userId? I am working with Spring webflux, so it also does not have the ReactiveCrudRepository for DynamoDb. My User table is something like this:
#Data
#NoArgsConstructor
#AllArgsConstructor
#DynamoDbBean
public class User {
private String userId;
private String userName;
private String password;
private String firstName;
private String lastName;
private String timestamp;
#DynamoDbPartitionKey
public String getUserId() {
return userId;
}
}
My repo class is:
#Repository
public class UserRepo {
private DynamoDbAsyncTable<User> userDynamoDbAsyncTable;
public UserRepo(DynamoDbAsyncTable<User> userDynamoDbAsyncTable) {
this.userDynamoDbAsyncTable = userDynamoDbAsyncTable;
}
// CREATE
public CompletableFuture<Void> save(User user) {
return userDynamoDbAsyncTable.putItem(user);
}
// READ
public CompletableFuture<User> getUserByID(String userId) {
return userDynamoDbAsyncTable.getItem(getKeyBuild(userId));
}
// UPDATE
public CompletableFuture<User> updateUser(User user) {
return userDynamoDbAsyncTable.updateItem(user);
}
// DELETE
public CompletableFuture<User> deleteUserById(String userId) {
return userDynamoDbAsyncTable.deleteItem(getKeyBuild(userId));
}
// GET_ALL_ITEM
public PagePublisher<User> getAllUser() {
return userDynamoDbAsyncTable.scan();
}
private Key getKeyBuild(String userId) {
return Key.builder().partitionValue(userId).build();
}
}
Is there any way to query database something like findByUserName("John") which returns the User object with "John" as a username?

Answer 1

You can't query without a partition key, if you have the partition key you can combine that with a sortKey, otherwise you will need to make your userName field a sortKey in Dynamo and use a GlobalSecondaryIndex to be able to search by userName alone.
#DynamoDbSortKey
public String getUserName() {
return serName;
}
You could use table.scan() but that's not recommended, the recommended way is to use a partition key + sortKey or sortKey + GlobalSecondaryIndex with the table method table.query().