https://github.com/g-khan/postgresql-vacuum-example
VACUUM reclaims storage occupied by dead tuples.
https://github.com/g-khan/postgresql-vacuum-example
Last synced: 8 months ago
JSON representation
VACUUM reclaims storage occupied by dead tuples.
- Host: GitHub
- URL: https://github.com/g-khan/postgresql-vacuum-example
- Owner: G-khan
- Created: 2022-08-29T10:42:29.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2022-08-31T14:57:28.000Z (about 3 years ago)
- Last Synced: 2025-02-17T18:09:11.206Z (8 months ago)
- Size: 2.93 KB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
## postgresql-vacuum-example
VACUUM reclaims storage occupied by dead tuples.
### PostgreSQL Vacuum Practices
To simply run the container using the Postgresql latest image, we can execute the following command:
```plaintext
docker run --name postgres-vacuum --rm -e POSTGRES_USER=postgres -e POSTGRES_PASSWORD=postgres -e PGDATA=/var/lib/postgresql/data/pgdata -v /tmp:/var/lib/postgresql/data -p 5432:5432 -it postgres:latest
```
to Execute to docker:
```plaintext
docker exec -it postgres-vacuum /bin/sh
```
### OR
for docker-compose.yaml:
```plaintext
version: '3.8'
services:
db:
image: postgres:latest
restart: always
environment:
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=postgres
ports:
- '5432:5432'
volumes:
- db:/var/lib/postgresql/data
volumes:
db:
driver: local
```
to run PostgreSQL via docker-compose:
```plaintext
docker-compose up -d
```
## Practice Time
go into the docker container
```plaintext
docker exec -it postgres-vacuum /bin/bash
```
and access the Postgres CLI:
```plaintext
psql --username postgres
```
Let's create a pg\_visibility extension to see the dead tuples.
```plaintext
CREATE EXTENSION pg_visibility;
```
Let's do a delete operation example with pg\_visibility.
Create a table:
```plaintext
postgres=# create table gokhanadev(id int, id2 int);
CREATE TABLE
```
And insert some data with generate\_series:
```plaintext
postgres=# insert into gokhanadev values(generate_series(1,1000000), generate_series(1,1000000));
INSERT 0 1000000
```
Check all visible tuples. **f** means visibility is false for the pages. **t** means visibility “true” for the pages. :
```plaintext
postgres=# select count(blkno), all_visible from pg_visibility_map('gokhanadev') group by all_visible;
count | all_visible
-------+-------------
4425 | f
(1 row)
```
Now we can update the data to see dead tuples:
```plaintext
postgres=# Update gokhanadev set id = id + 1 where id > 50000;
UPDATE 950000
```
Let's check the dead tuples via pg\_visibility\_map:
```plaintext
postgres=# select count(blkno), all_visible from pg_visibility_map('gokhanadev') group by all_visible;
count | all_visible
-------+-------------
8408 | f
221 | t
(2 rows)
```
You can wait a few minutes for the auto-vacuum or execute the Vacuum comment
```plaintext
postgres=# VACUUM gokhanadev;
VACUUM
```
Take a look, what happened after the vacuum:
```plaintext
postgres=# select count(blkno), all_visible from pg_visibility_map('gokhanadev') group by all_visible;
count | all_visible
-------+-------------
8629 | t
(1 row)
```
## More about Vacuum
* **Verbose** the Vacuum to Print a detailed vacuum activity report for each table.
```plaintext
VACUUM VERBOSE table_name
```
* **ANALYZE** the Vacuum to Update statistics used by the planner to determine the most efficient way to execute a query.
```plaintext
VACUUM ANALYZE table_name
```
* **Full VACUUM**: Locks the database table, and reclaims more space than a plain VACUUM. Be careful for production.
```plaintext
VACUUM(FULL) table_name
```
* Set the auto vacuum
```plaintext
ALTER TABLE table_name SET (autovacuum_enabled = false);
```
[More about the vacuum](https://www.postgresql.org/docs/current/sql-vacuum.html)