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Joe Ardent 2023-06-26 12:16:33 -07:00
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content/rnd/a_serialized_mystery/index.md
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@ -24,7 +24,7 @@ folly](@/sundries/a-thoroughly-digital-artifact/index.md)!
# Keys, primarily # Keys, primarily
Most large distributed programs that people interact with daily via HTTP are, in essence, a fancy Most large distributed programs that people interact with daily via HTTP are, in essence, a fancy
facade for some kind of database. Facebook? Database. Gmail? Database. facade for some kind of database. Facebook? That's a database. Gmail? That's a database.
![that's a database][thats_a_database] ![that's a database][thats_a_database]
<center><span class="caption">wikipedia? that's a database.</span></center> <center><span class="caption">wikipedia? that's a database.</span></center>
@ -35,7 +35,8 @@ it's in. Since databases typically contain multiple tables, and primary keys hav
within their own table, you could just use a simple integer that's automatically incremented every within their own table, you could just use a simple integer that's automatically incremented every
time you add a new record, and in many databases, if you create a table without specifying a primary time you add a new record, and in many databases, if you create a table without specifying a primary
key, they will [automatically and implicitly use a key, they will [automatically and implicitly use a
mechanism](https://www.sqlite.org/lang_createtable.html#rowid) like that. mechanism](https://www.sqlite.org/lang_createtable.html#rowid) like that. You may also recognize the
idea of "serial numbers", which is what these sorts of IDs are.
This is often totally fine! If you only ever have one copy of the database, and never have to worry This is often totally fine! If you only ever have one copy of the database, and never have to worry
about inserting rows from a different instance of the database, then you can just use those simple about inserting rows from a different instance of the database, then you can just use those simple
@ -47,12 +48,12 @@ fancier identifier for your primary keys, to avoid collisions between primary ke
## UUIDs ## UUIDs
One very common type for these is called a A popular type for these is called a
[UUIDv4](https://datatracker.ietf.org/doc/html/rfc4122#page-14). These are 128-bit random [v4 UUIDs](https://datatracker.ietf.org/doc/html/rfc4122#page-14). These are 128-bit random
numbers[^uuidv4_random], and when turned into a string, usually look something like numbers[^uuidv4_random], and when turned into a string, usually look something like
`1c20104f-e04f-409e-9ad3-94455e5f4fea`; this is called the "hyphenated" form, for fairly obvious `1c20104f-e04f-409e-9ad3-94455e5f4fea`; this is called the "hyphenated" form, for fairly obvious
reasons. Although sometimes they're stored in a DB in that form directly, that's using 36 bytes to reasons. Although sometimes they're stored in a DB in that form directly, that's using 36 bytes to
store 16 bytes' worth of data, which is more than twice as many bytes than necessary. And if you're store 16 bytes' worth of data, which is more than twice as many bytes as necessary. And if you're
a programmer, this sort of conspicous waste is unconscionsable. a programmer, this sort of conspicous waste is unconscionsable.
You can cut that to 32 bytes by just dropping the dashes, but then that's still twice as many bytes You can cut that to 32 bytes by just dropping the dashes, but then that's still twice as many bytes
@ -83,4 +84,8 @@ desire to be "efficient".
[^uuidv4_random]: Technically, most v4 UUIDs have only 122 random bits, as six out of 128 are [^uuidv4_random]: Technically, most v4 UUIDs have only 122 random bits, as six out of 128 are
reserved for version metadata. reserved for version metadata.
[^blob-of-bytes]: Some databases have direct support for 128-bit primitive values (numbers). The
database I'm using, SQLite, only supports up to 64-bit primitive values, but it does support
arbitrary-length sequences of bytes called "blobs".
[thats_a_database]: ./thats_a_database.png "that's a database" [thats_a_database]: ./thats_a_database.png "that's a database"