Recall that Postgres’ DDL, including all the partitioning commands above is transactional, which let me to write very thorough tests easily, so the implementation is well-vetted. The entirety of this scheme took me a few hours to write, and has been running for weeks, entirely problem-free. INSERTs and UPDATEs all happen on the parent table, so partitioning is completely abstracted away from normal application logic. Partitions outside the retention window are detached: ALTER TABLE widgetĭetached partitions are kept around for three days in case an operator wants to inspect them, then dropped with the standard: DROP TABLE widget_20221005 Creating new partitions is easy: CREATE TABLE widget_20221005 PARTITION OF widget
It wakes every ten minutes, and run through these steps:Ĭalculates which new partitions should be created (if any) and creates them, bringing future partitions up three days in advance to give us some buffer in case something goes wrong. pgpartman), opting instead to just add a small background job to our existing worker framework. We added our first partitioned table recently, and things have gotten so good that we skipped bringing in a partition-managing extension (e.g. It’s largely been a story of getting partitioned tables up to feature parity with non-partitioned tables, and they’re now very, very close.
POSTGRESQL ALTER TABLE PARTITION BY RANGE UPDATE
Postgres 11: UPDATE statements can move rows between partitions.
Postgres 11: INSERT on the parent partitioned table routes rows to their appropriate partition.Postgres 11: Support for PRIMARY KEY, FOREIGN KEY, indexes, and triggers on partitioned tables.Postgres 10: Brings in the original CREATE TABLE.Here’s a sprinkling of new features that have come into Postgres over the last five years: And even once Postgres got support for native partitioning, things were always harder – routing inserts/updates, adding/removing partitions, adding indexes, support for features like foreign keys and triggers, etc.īut, a lot of work has gone into improving the operator experience since partitioning was introduced.
POSTGRESQL ALTER TABLE PARTITION BY RANGE MANUAL
Not long ago there was no formal partitioning at all in Postgres – it was entirely a user-level construct which needed all kinds of manual plumbing to run. It executes instantly, and with negligible costs (partitioning has other benefits too). Each row removal land in the WAL, resulting in significant amplification.īut with partitions, deletion becomes a simple DROP TABLE. A long running query must iterate through and mark each one as dead, and even then nothing is reclaimed until an equally expensive vacuum runs through and frees space, and only when it’s allowed to after rows are no longer visible to any other query in the system, whether they’re making use of the large table or not.
In Postgres, trying to remove old rows from a large, hot table is flitting with disaster. Partitioned tables aren’t an everyday go to, but are invaluable in some cases, particularly when you have a high volume table that’s expected to keep growing.
0 kommentar(er)
