CODEWITHSUNDEEP
nosqlamazon-dynamodbdynamodb-queries
Eitan
Eitan

Reputation: 1494

Modeling entities and tags in DynamoDB

I have an app that contains entities such as "catalogs", "collections", etc. I'd like to model relationships between entities using tagging. So for example I might have a sales catalog and a sales collection. I would know both entities are connected because they both have the same tag: "sales".

Here are the queries I need to do:

1) Get All Entities of a certain type i.e. catalogs

2) Get Entity By Id

3) Get all entities with a certain tag

4) Query a list of entities by a certain tag and retrieve the rest of the tags associated with that entity.

I'm wondering how to model this in Dynamo DB

I first thought I could do this:

PK = entityType_id (e.g. catalog_1)
SK = Tag (e.g. sales)

The problem is I can't get get all entities of a certain type. (1)

I thought maybe I could do this:

PK = entityType (e.g. catalog)
SK = id_tag (e.g. 1_sales)

I could accomplish: 1,2above using BeginsWith and EndsWith on the SK and 3 using a GSI where the type tag is PK but couldn't accomplish 4.

In the future I'd also like to possibly be able to query by tag type. I don't see how all of this is possible in one table like Amazon recommends or without using an RDBMS.

I'd really appreciate any input or direction I can get.

Thanks!

Upvotes: 1

Views: 1480

Answers (1)

best wishes
best wishes

Reputation: 6634

you can use this as your schema

|    pk   |     sk               |     GSI1 PK          | 
|  uid1   |    metadata          |                      |   tags:["sales","purchase", "borrow"] | entityType:["catalogs"]
|  uid1   |entityType#catalogs   | entityType#catalogs
|  uid1   |    tag#sales         | tag#sales
|  uid1   |    tag#purchase      | tag#purchase
|  uid1   |    tag#borrow        | tag#borrow
|  uid2   |entityType#collection | entityType#collection
|  uid2   |    tag#borrow        | tag#borrow
|  uid2   |    metadata          |                      |   tags: ["borrow"] | entityType:["collection"]

where PK is SK of GSI1 (GSI1: global secondary index)

This will solve use cases like

  1. Get all entity of sales

    Select* where PK=entityType#sales in table GSI1

  2. Get entity by id

    Select * wehere PK=id and SK=metadata

  3. Get all entities with a tag Sales

    Select* where PK=tag#sales in table GSI1

  4. Query a list of entities by a certain tag and retrieve the rest of the tags associated with that entity.

    Use 3rd query and get all list of uids and then do a get all tags, or duplicate tags data as well in every row.

Upvotes: 2

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