How to think in data stores instead of databases?

Question

As an example, Google App Engine uses Google Datastore, not a standard database, to store data. Does anybody have any tips for using Google Datastore instead of databases?

Answer 1

I came from Relational Database world then i found this Datastore thing. it took several days to get hang of it. well there are some of my findings.

You must have already know that Datastore is build to scale and that is the thing that separates it from RDMBS. to scale better with large dataset, App Engine has done some changes(some means lot of changes).

RDBMS VS DataStore
Structure
In database, we usually structure our data in Tables, Rows which is in Datastore it becomes Kinds and Entities.

Relations
In RDBMS, Most of the people folllows the One-to-One, Many-to-One, Many-to-Many relationship, In Datastore, As it has "No Joins" thing but still we can achieve our normalization using "ReferenceProperty" e.g. One-to-One Relationship Example .

Indexes
Usually in RDMBS we make indexes like Primary Key, Foreign Key, Unique Key and Index key to speed up the search and boost our database performance. In datastore, you have to make atleast one index per kind(it will automatically generate whether you like it or not) because datastore search your entity on the basis of these indexes and believe me that is the best part, In RDBMS you can search using non-index field though it will take some time but it will. In Datastore you can not search using non-index property.

Count
In RDMBS, it is much easier to count(*) but in datastore, Please dont even think it in normal way(Yeah there is a count function) as it has 1000 Limit and it will cost as much small opertion as the entity which is not good but we always have good choices, we can use Shard Counters.

Unique Constraints
In RDMBS, We love this feature right? but Datastore has its own way. you cannot define a property as unique :(.

Query
GAE Datatore provides a better feature much LIKE(Oh no! datastore does not have LIKE Keyword) SQL which is GQL.

Data Insert/Update/Delete/Select
This where we all are interested in, as in RDMBS we require one query for Insert, Update, Delete and Select just like RDBMS, Datastore has put, delete, get(dont get too excited) because Datastore put or get in terms of Write, Read, Small Operations(Read Costs for Datastore Calls) and thats where Data Modeling comes into action. you have to minimize these operations and keep your app running. For Reducing Read operation you can use Memcache.

Answer 2

The way I have been going about the mind switch is to forget about the database altogether.

In the relational db world you always have to worry about data normalization and your table structure. Ditch it all. Just layout your web page. Lay them all out. Now look at them. You're already 2/3 there.

If you forget the notion that database size matters and data shouldn't be duplicated then you're 3/4 there and you didn't even have to write any code! Let your views dictate your Models. You don't have to take your objects and make them 2 dimensional anymore as in the relational world. You can store objects with shape now.

Yes, this is a simplified explanation of the ordeal, but it helped me forget about databases and just make an application. I have made 4 App Engine apps so far using this philosophy and there are more to come.