#Postgres generate uuid primary key update

Also, you won't be able to usefully use constraint exclusion on searches for the key if writing only to one partition at a time, so you'll still have to search all the partitions' indexes for a key when doing queries. Partitioning won't help much unless you can confine writes to one partition. You shouldn't use one if you don't require one, but if you cannot rely on a central source of synthetic keys and there is no suitable natural key to use, it's still the way to go. If you need a UUID key, you need a UUID key. Is there any way to remedy or are UUIDs simply not a good PK on a large, un-partitioned table? Writes will tend to be random within indexes, not appends to hot, recently accessed rows The b-tree index that implements the primary key will be 4x as large (vs a 32-bit key), taking longer to search and requiring more memory to cache.

The uuid is 4 times as wide as a typical 32-bit integer synthetic key, so the row to write is 12 bytes bigger and you can fit fewer rows into a given amount of RAM It still does have a performance cost because of the need to maintain the PK, and because the inserted tuple is bigger. So I imagine that in Postgres using a UUID PK does not hurt the performance of that insert. Whereas with a sequential key the index will only be updated at the tip which will always be in memory.Īssuming that I understand the performance impact on the index correctly, is there any way to remedy that or are UUIDs simply not a good PK on a large, un-partitioned table?Īs I understand it, Postgres does not maintain row clustering on inserts Add a unique-indexed UUID id field to allow you to search by a UUID id, instead of a numeric primary key.

#Postgres generate uuid primary key update

As I understand it, Postgres does not maintain row clustering on inserts, so I imagine that in Postgres using a UUID PK does not hurt the performance of that insert.īut I would think that it makes the insert into the index that the primary key constraint creates much more expensive once the table is large, because it will have to constantly be read from disk to update the index on insertion of new data. In DBMS's that use clustered storage for table records it is a given that using a UUID is going to increase the cost of inserts due to having to read from disk to find the data page into which to perform the insert, once the table is too big to hold in memory. I am wondering about the performance impact of using a non-sequential UUID as the primary key in a table that will become quite large in PosgreSQL.