PGCon2016 - 20180510

PGCon 2016
The PostgreSQL Conference

Kevin Grittner
Day Talks - Day 1 - 2016-05-19
Room DMS 1160
Start time 11:00
Duration 00:45
ID 941
Event type Lecture
Track 9.6 Features
Language used for presentation English

ERROR: snapshot too old

(why having the option of seeing that is a good thing)

This talk will cover the reasons why someone might want to enable timeout of old snapshots, and how this is implemented.

Many people have experienced the pain of extreme bloat due to one unnoticed connection lingering in "idle in transaction" state or a long-running report set that isn't even operating off of tables currently under modification -- and the resulting need to schedule a maintenance window to clean up that bloat. A new configuration option called oldsnapshotthreshold aims to allow DBAs to configure their systems to prevent that pain with minimal impact on operations. The error will not be seen unless a snapshot is past the specified age and is used to query data from a page which has been modified since the snapshot was taken -- so those reports running off of materialized summary data can run for as long as they need, without causing any bloat.

NOTE: Sorry, we did not capture video for this talk.