Canonical-or-best data type to store a Flake ID in PostgresSQL for two query patterns



  • I want to generate and write https://github.com/boundary/flake to a column from clients connected to my PostgreSQL database. These IDs are essentially a large globally-unique numbers that grow with time, similar to a monotonically increasing ID but without any coordination.

    The two most common query patterns would look this:

    • Sort by the Flake ID SELECT * ORDER BY flake_id
    • Group by another column, and then select the maximum Flake ID in each group. SELECT max(flake_id) GROUP BY some_other_column

    There seem to be a few possible ways to do this:

    • bigint with two columns. Simple to order by, but unclear how to select maximum across two words after a group-by.
    • bytea with 16 bytes.
    • bit(n) where n=128
    • uuid happen to be 128-bit, and testing yields ORDER BY results, but there is no max function that can be applied to it
    • encoded as a string, and stored in text haven't tested it but a max function seems nonsensical unless it uses a lexicographic order. It also seems a bit dirty to use a string to encode what is order-able on its own numerically.

    There's a bit of choice paralysis in the options and how they interact with indexes to perform the above query patterns most efficiently.

    I am looking for insight into the ideal data-type considering the above query patterns, and how it would interact with the relevant indexes.



  • If you want to go with two bigints, create a composite type for flake_id:

    CREATE TYPE pair (a bigint, b bigint);
    

    Your first query then can remain as it is, and your second query could be rewritten to

    SELECT DISTINCT ON (some_other_column)
           flake_id
    ORDER BY some_other_column, flake_id DESC;
    

    But why don't you use the obvious data type numeric?




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