How to set the unique property to DynamoDB using dynamoose node module which it 'll helps in eliminating duplicate entry?
You can create a table whose schema uses the attribute you want to keep unique as the primary key. Or, to separate business logic from your schema design you can use a content-based key that hashes the unique property using SHA256, and use the hash value as the partition of your table.
Related
I am using Postgres and I have a table with a unique key (memberId, propertyName). I am using onDuplicateKey and the generated code shows it is using on conflict but it uses the id. Is it possible to specify your own keys to check or does Jooq try to read the table and check that there are unique constraints? My current workaround is doing a select then doing an update or an insert.
The ON DUPLICATE KEY syntax is derived from MySQL, where the semantics of the clause is to consider all the unique constraints (including primary key) on the table, not just the ones you care about.
But why use this syntax in the first place, when you're targeting PostgreSQL? jOOQ supports PostgreSQL's ON CONFLICT, which allows for specifying which unique key to use for the clause.
I am trying to create an unique key for an whole collection in Cosmos DB.
So not unique per _pk.
I read this article but here it only writes about Unique key per partition: https://learn.microsoft.com/en-us/azure/cosmos-db/unique-keys.
I Googled a lot but I can't find any result about a uk on collection. Is this even possible? And if it is, is there any documentation about it?
I think the official doc about cosmos db unique key is clearly stated.
I am trying to create an unique key for an whole collection in Cosmos
DB.
Unique keys must be defined when the container is created, and the unique key is scoped to the partition key.
In the same collection there must be possible to store different
objects without an username.
Sparse unique keys are not supported. If values for some unique paths are missing, they are treated as a special null value, which takes part in the uniqueness constraint.
If you do want to make the username field unique in the whole collection across the partitions and even null value is permitted, I think you need to check the uniqueness by yourself before inserting documents into cosmos db.I suggest you using pre-triggers to do the check.
Hope it helps you.
How do I check for existing documents with duplicate User ID before inserting a document? In the RDBMS world, I would generally have a unique constraint to ensure that there are no duplicates in the table.
In Couchbase, there is a unique constraint on what is in effect the primary key of the document: its ID (or key) must indeed be unique.
Latest versions of most SDKs (eg for Java it's 2.2.0) now have an exist operation that can be used to check if a particular key is stored. Otherwise you have operations like `
I am trying to put my domain model into Cassandra using CQL. Let's say I have USER_FAVOURITES table. Each favourites has ID as a PRIMARY KEY. I want to store the list of up to 10 records of multiple fields, field_name, field_location and so on in order.
Is this a good idea to model a table like this
CREATE TABLE USER_FAVOURITES (
fav_id text PRIMARY KEY,
field_name_list list<text>,
field_location_list list<text>
);
And object is going to be constructed from list items of matching indicies (e.g.
Object(field_name_list[3],field_location_list[3]))
I query favourites always together. I may want to add and item to some position, start, end or middle.
Is this a good practice? Doesn't look like, but I am just not sure how to group objects in this case, also when i want to keep them in order by, for example, field_location or more complex ordering rule
I'd suggest the following structure:
CREATE TABLE USER_FAVOURITES (
fav_id text PRIMARY KEY,
favs map<int, blob>
);
This would allow you to get access to any item via index. The value part of map is blob, as one can easily serialize a whole needed object into binary and deserialize later.
My personal suggestion will be don't emphasize too much on cassandra collection, as it is bloom further in future. Though above specified scenario is very much possible and no harm in doing so.
I am using node and planning to use redis to store data [data will be in the SQL or oracle table format with many fields like ID, name, City, Marks, etc].
Found that we can store only key and value in redis with three data structures [in list, set or sorted set].
Is it possible for me to store like Table name [Key name] : Details
and values like ID : 1, Name : john, Country:Russia,
ID : 2, Name : Rose , Country:US , etc.
Is there any other data structure apart from list, set and sorted set in redis?
Yes. See the docs.
http://redis.io/topics/data-types
You also have the Hash data structure...
Database tables are used to store Entities. A loose definition of an Entity is something that has a unique primary key. In Redis, Entities are usually stored using Hash data structure, where columns in the database become fields in the Hash. The primary key is stored in the key of the hash.
Database tables also store non-entities, such as relationships between Entities. For example one-to-many relationship is typically done using a foreign key. In Redis, such relationships can be modeled in Sets, Lists or SortedSets.