RE: UUID vs. Sequential ID as Primary

In the case of a single thread to produce 1 million inserts the increment by of the sequence could be 1 million.  

You need to make your tests correspond at least slightly to a simulation of your predicted actual operational reality.  

In general predictions of simplifying any operational reality to produce a testing scenario are important. It is possible that your operational reality requires you to buy a loaf of bread one slice at a time, but I doubt it.  

mwf  

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of ahmed.fikri_at_t-online.de Sent: Saturday, April 13, 2024 9:10 AM
To: list, oracle
Subject: AW: UUID vs. Sequential ID as Primary  

If the UUID method already outperforms sequences in a single session, then the performance of the sequence method will be even worse in multiple concurrent sessions. Additionally, UUIDs are generated on the client side. Therefore, I believe that conducting the test with only one session is sufficient. My aim was simply to confirm that UUIDs are a better choice for microservice architecture  

Regards

Ahmed          

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Betreff: Re: UUID vs. Sequential ID as Primary

Datum: 2024-04-13T14:53:59+0200

Von: "Jonathan Lewis" <jlewisoracle_at_gmail.com>

An: "list, oracle" <oracle-l_at_freelists.org>      

Did you use a reasonable number of concurrent sessions in your testing?  

Testing with just a single session is an easy trap to fall into, and with things like sequences (Oracle sequences particularly) the effects of concurrency on performance of inserts and size of index can be dramatic as you go from single session to even a fairly small number of concurrent sessions. (The same effect may appear with UUIDs on some platforms depending on how the UUID is generated.)  

Regards

Jonathan Lewis      

On Sat, 13 Apr 2024 at 09:37, ahmed.fikri_at_t-online.de <ahmed.fikri_at_t-online.de> wrote:

Hi,    

For those who need to decide which primary key type to choose, I conducted a test myself, initially on PostgreSQL, and I believe the results would be similar for Oracle.

The test involved creating and saving 1 million records using Java (with Hibernate) as the client:  

strategy

Field Type

entities creation elapsed time (ms)

saving entities
elapsed Time (ms)

Table Size
(mb)

Index Size
(mb)

UUID String

7768

181184

80

73

UUID UUID 7763

172367

57

37

Sequence

Long

10036

163351

49

21  

UUIDs consist of two Longs, which means they require double the space compared to a single Long. However, despite this overhead, we observed that the creation of entities using UUIDs at the client-side is faster compared to using sequences. This is due to the fact that UUIDs allow for client-side ID generation, reducing the need for round trips to the database during entity creation (Despite efforts to minimize its impact for sequences, we still observe its effect).

On the other hand, saving entities with Long IDs takes less time than UUIDs. This is because Longs require less storage space and hence result in quicker database operations.  

In my case, working with microservices and distributed systems, the preferred primary key type turned out to be UUID  

Regards

Ahmed        

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Betreff: Re: UUID vs. Sequential ID as Primary

Datum: 2024-04-11T21:36:16+0200

Von: "Jonathan Lewis" <jlewisoracle_at_gmail.com>

An: "list, oracle" <oracle-l_at_freelists.org>      

When considering the overheads and side effects of sequences it's worth remembering that in 12c Oracle introduced the "scale" and "extend" options to prepend the instance id and session id to the generated value so that contention between instances and between sessions on the same instance would be minimised.  

It's also worth remembering that 19c introduced an automatic resizing strategy for the sequence cache (which introduced problems for some people, especially in RAC) to work around the contention at sites that didn't set a sensible cache size for their sequences. (See comments on this note: Sequence Accelerator | Oracle Scratchpad (wordpress.com) <https://jonathanlewis.wordpress.com/2021/08/06/sequence-accelerator/> )  

Regards

Jonathan Lewis        

On Thu, 11 Apr 2024 at 18:53, ahmed.fikri_at_t-online.de <ahmed.fikri_at_t-online.de> wrote:

Thank you all for your insightful responses. I share the concern about mistakenly assuming uniqueness, as it could have serious consequences down the line.

As for Peter's suggestion, the challenge lies in the fact that the client doesn't handle the insertion process; it simply needs to generate a unique ID for an entity without directly "interacting" with the database. This can be achieved if the client understands how IDs are generated, such as being aware of a sequence on the database side and can access that sequence. However, when using identities, there's a significant hurdle because the client lacks access to the internally generated sequence, even if one is utilized server-side. Consequently using IDENTITY leads to poor performance as just creating a row at client side require round trip to the database (The client determines when and whether to insert eventual rows into the database, so it creates a sort of local cache that should, at a certain point, mirror the database). The system only functions smoothly if the client can interact with the sequence directly.  

Personally, I lean towards using sequences, but I hesitate to recommend them to others without being able to precisely justify why. Perhaps there's a benefit to using UUIDs that I'm not yet aware of.        



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