![]() ![]() With respect to your actual question, I usually generate my UUIDs in code and then store them in MySQL. Now, we create our domain class using Hibernate annotations to map it to our existing MySQL table. There is technically an incredibly small possibility of collision using SHA-256, but I don't consider it an issue for my purposes. Since we know the format of the UUID when represented as a String, we know that it has a length of 36 characters, so we can define the column as VARCHAR (36). Now, you have a predictable directory structure based upon the SHA-256 hash of each file and you can write a simple service that can easily store and retrieve any file based upon its hash and extension. ![]() I answered, after trying it, UPDATE table SET uuidcol UUID () It worked for me, but about half (it seems) people report that it doesn't work, saying the ID is identical on all rows. In the database, you would still use a UUID primary key if you prefer, but also store both the hash and the extension in separate columns. 2 4 years ago, I answered a question on SO, 'how to set an UUID for each row in bulk'. It also prevents duplication of files since they would have the same hash. This makes sure you don't have too many files in any single directory, which would slow down comparisons and searches. You then use UUIDTOBIN () or BINTOUUID () to convert from binary to the text human readable UUID stuff. For example, a file with the hash 9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08 would be stored in the following directory structure. You can store as CHAR (36) or store as VARCHAR (36) (both make sense) or store as STRING (probably better to use CHAR (36)) but you can store it as BINARY (16) as well. Name the file based upon its SHA-256 hash (VARCHAR 64), and store it in a series of nested folders whose names are 5 characters in length. Others may have better advice, but here is a slightly different option to consider that I use for an app of mine that has to manage tens of thousands of images. When you get to a certain size of scale, UUID's don't make sense because they're not stable enough.īut also, on a wordpress blog? UUID's are probably overkill because a UINT with autoincrement is perfectly stable, informationally very dense, and fairly solid. Their tweet IDs are probably a mix of time + app node generating the tweet + user + random component for the unique ID (at least). If you're at facebook or twitter, I highly doubt they're generating UUIDv4's for their tweets. but alas.Īnd UUIDv4 doesn't fit everywhere. And then they should support AUTO_INCREMENT on that datatype. Ideally MySQL would have a UUIDv4 datatype (like Postgres and others) but not yet. It's more efficient, and slightly better, but it's almost for sure not going to be the source of any performance issues. You then use UUID_TO_BIN() or BIN_TO_UUID() to convert from binary to the text human readable UUID stuff. ![]() You can store as CHAR(36) or store as VARCHAR(36) (both make sense) or store as STRING (probably better to use CHAR(36)) but you can store it as BINARY(16) as well. Note, UUID's do not actually "increment" each one's random, plus there's no UUID datatype afaik. Op mentioned "auto-incrementing UUID function". ![]()
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