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Why are UUIDs not used as primary keys?
For each of these columns in a set of table with billions of accounts, the extra size of foreign keys adds up fast. Another problem is fragmentation — because UUIDs are random, they have no natural ordering so cannot be used for clustering.
Why is it good to use a UUID as a PK?
Reasons UUIDs are Good. There are several reasons using a UUID as a PK would be great compared to auto-incrementing integers: At scale, when you have multiple databases containing a segment (shard) of your data, for example a set of customers, using a UUID means that one ID is unique across all databases, not just the one you’re in now.
How to generate a primary key in JPA?
The default way in JPA for primary keys is to use the @GeneratedValue annotation with the strategy attribute set to one of AUTO, IDENTITY, SEQUENCE, or TABLE. You pick the most appropriate strategy for your situation and that’s it. But you can also choose to generate the primary key yourself.
Can a PK be used as a primary key?
A primary key is, by definition unique within its scope. It is, therefore, an obvious thing to use as a customer number, or in a URL to identify a unique page or row. Don’t! I would argue that using a PK in any public context is a bad idea. The original issue with simple auto-incrementing values is that they are easily guessable as I noted above.
When do you really need a UUID / GUID?
If the hashing strategy is well know amongst components in the architecture, you will not need to store the hash (since components will know how to regenerate it on the fly when performing lookups). 3. When you need to present an ID to a user.
How are hash functions used in data vault?
To guarantee a consistent join performance, the solution is to combine the business keys into a single column value by using hash functions to calculate a unique representation of a business object. Due to the independence during the load process of hubs, links and satellites, it is possible to do that all in parallel.