What is the algorithm used for converting uuid::text in Postgresql?

Question

A table in postgresql where one of columns is uuid as BYTEA is being exported to tsv.

For example uuid was: 625c3430-34d0-43eb-b85d-e3bd1d9f82e1 and exported value is: b\\404\320C\353\270]\343\275\035\237\202\341.

What is the algorithm behind converting uuid::text and for the reverse functionality also, from text to uuid. I have to read this tsv, decode uuid from its text representation and "do additional stuff" depending on decoded uuid.

Are there some libraries for this in Java or do I need to write my own decoder for it? If I have to write my own decoder any hints on algorithm for it are welcome.

FYI, Postgres efficiently stores the 128-bit UUID values in the UUID data type. For generating values, most folks use either the uuid-ossp extension for a wide array of support of various Versions of UUIDs, or the pgcrypto extension for random-based Version 4 only. — Basil Bourque
– Basil Bourque, Commented Sep 6, 2019 at 21:22

Nedzad G · Accepted Answer · 2019-09-06 21:13:48Z

1

Convert your initial uuid to byte array. Check every element of byte array and if the value is:

0 => "\000"

39 => "\047"

or '''' (single quote symbol)

92 => "\" or "\134" (backslash)

31 < value < 127 => character from value

any other is "\xxx" octal value.

And you have your "text representation" uuid.

To get uuid from "text representation" just go trough the steps in reverse.

answered Sep 6, 2019 at 21:13

Nedzad G

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