public inbox for [email protected]
help / color / mirror / Atom feedFrom: Matt Hughes <[email protected]>
To: [email protected]
Subject: Planning of sub partitions
Date: Fri, 5 Jul 2024 11:24:23 -0400
Message-ID: <CANi6QLzHH1QySGK3r_WWu+FKxvCRXNBzvEY2dhFAA3XGuShg_g@mail.gmail.com> (raw)
I am trying to model a stateful `event` table using partitions. An event
has date_raised (not null) and date_cleared (nullable) columns. An event
is in the "open" state when it has a null date_cleared; it is in the
"closed" state when date_cleared is set. Once date_cleared is set, it
won't change.
While most events close after a short period of time, a few stragglers stay
open for weeks or months. I'm trying to optimize my system for the
following things:
- I need to drop events older than N days; I want to use partitions so I
can just drop the table rather than an expensive DELETE
- Users want to see all open events OR closed events within the past N days
To do this, I came up with the following schema:
create table event (
id uuid not null,
cleared boolean not null,
date_raised timestamp without time zone not null,
date_cleared timestamp without time zone,
primary key (id, date_raised, cleared)
) PARTITION BY LIST (cleared);
CREATE TABLE event_open PARTITION OF event FOR VALUES IN (false);
CREATE TABLE event_closed PARTITION OF event FOR VALUES IN (true) partition
by range(date_raised);
CREATE TABLE event_closed_y2024_m01 PARTITION OF event_closed FOR VALUES
FROM ('2024-01-01') to ('2024-02-01');
CREATE TABLE event_closed_y2024_m02 PARTITION OF event_closed FOR VALUES
FROM ('2024-02-01') to ('2024-03-01');
This works for the most part but the plan for my compound query does not
behave as I would expect:
-- 1. correctly only picks event_open partition
explain select * from event where cleared is false;
-- 2. correctly picks all event_closed_* partitions
explain select * from event where cleared is true;
-- 3. correctly picks just the event_closed_y2024_m01 partition
explain select * from event where cleared is true and date_raised >
'2024-01-01' AND date_raised < '2024-01-02';
-- 4. uses all partitions; should exclude event_closed_y2024_m02
explain select * from event
where
cleared is false OR
(cleared is true and date_raised > '2024-01-01' AND date_raised <
'2024-01-02');
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Append (cost=0.00..110.91 rows=2322 width=25)
-> Seq Scan on event_open event_1 (cost=0.00..33.10 rows=774 width=25)
Filter: ((cleared IS FALSE) OR ((date_raised > '2024-01-01
00:00:00'::timestamp without time zone) AND (date_raised < '2024-01-02
00:00:00'::timestamp without time zone)))
-> Seq Scan on event_closed_y2024_m01 event_2 (cost=0.00..33.10
rows=774 width=25)
Filter: ((cleared IS FALSE) OR ((date_raised > '2024-01-01
00:00:00'::timestamp without time zone) AND (date_raised < '2024-01-02
00:00:00'::timestamp without time zone)))
-> Seq Scan on event_closed_y2024_m02 event_3 (cost=0.00..33.10
rows=774 width=25)
Filter: ((cleared IS FALSE) OR ((date_raised > '2024-01-01
00:00:00'::timestamp without time zone) AND (date_raised < '2024-01-02
00:00:00'::timestamp without time zone)))
Is this a bug? Query 4 is just a union of queries 2/3 which pick the right
partitions. Do you see anything else wrong with this approach?
Note that `closed` column is somewhat of a hack as it is completely
computeable from `date_cleared is not null`. However, as I understand it,
partitions can only be declared on values that are part of the primary
key.
view thread (2+ messages) latest in thread
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected]
Subject: Re: Planning of sub partitions
In-Reply-To: <CANi6QLzHH1QySGK3r_WWu+FKxvCRXNBzvEY2dhFAA3XGuShg_g@mail.gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox