![]() When I look at a request on the network tab in chrome developer tools I see a message that says provisional headers shown: In order to gain the benefits of using UUID primary keys with lower keyspace fragmentation perhaps Drew points out that it is better to use uuid_generate_v1mc() from the uuid-ossp extension because underneath it is using a time based seq algorithm which you can read about in the postgresql documentation.This is a weird one. This fragmentation however is not so good for efficiency of the database system itself. This makes sense due to the random probability distribution of the keys, it should be fragemented. So all inserts go to the same data page without random io. ![]() ![]() Use uuid_generate_v1mc() … the keys are seq because they’re time based. Random produces very fragmented inserts that destroy tables. It was pointed out by (thank you Drew!) that using gen_random_uuid() from pgcrypto has a negative side effect with respect to keyspace fragmentation on disk for the tables. We see that each row has a UUID id field which is the primary key and was automatically generated for us. Let’s examine our table now, SELECT * FROM snw.contacts We can now add entries into our newly created Stark & Wayne Contacts table, INSERT INTO snw.contacts (name,email) VALUES Id UUID PRIMARY KEY DEFAULT gen_random_uuid(), Let’s create a table with a UUID primary key and see how we use the gen_random_uuid() function to populate our IDs for us, CREATE SCHEMA IF NOT EXISTS snw Once you have done this you can generate a random id, SELECT gen_random_uuid() Once it has been loaded into a running instance of the database server it will be there for use from then on spanning restarts.Īlso be aware that if you have dumped and restored the database from one server to another running instance then depending on the method of the dump/restore you may need to load it into this new instance after restoring. Note specifically that the extension must be created (loaded) once for each database in which you wish to use it. This is how you load pre-compiled shared library code which adds functionality into your PostgreSQL database. So how do we use this function? First we need to create the extension in the database we wish to use it with, CREATE EXTENSION pgcrypto ( Update: See below.) For generating UUID’s within the database an easy place to start is to use the gen_random_uuid () function from the pgcrypto extension. Only use uuid-ossp if you have a real and specific need for the functions it provides If your only need is to generate and index them then you do not need uid-ossp. Generating them within our application will work quite nicely and is a good way to go, unless you want the database to handle creating these automatically for you which is usually where our point of view. Within the database using the extension pgcrypto.Within the database using the extension uuid-ossp.We then have three options for generating UUID’s, PostgreSQL out of the box defines a UUID Data Type which is a great start. While discussing the article the question came up about how to go about using UUID keys in our applications and what we have to do within PostgreSQL in order to use them. This weekend Dr Nic shared with us a well written article discussing the shortcomings of auto-incrementing (serial) keys and an alternative approach.
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