PostgreSQL Cheatsheet: Panduan Cepat untuk Pengembang
Referensi cepat ke postgresql
Konten Halaman
Referensi cepat untuk keperluan sehari-hari PostgreSQL kerja: koneksi, sintaks SQL, perintah meta psql, kinerja, JSON, fungsi jendela, dan lainnya.
Sebuah cheatsheet SQL yang ringkas mencakup perintah dan operasi paling esensial juga tersedia.
Koneksi & Dasar
# Koneksi
psql -h HOST -p 5432 -U USER -d DB
psql $DATABASE_URL
# Dalam psql
\conninfo -- tampilkan koneksi
\l[+] -- daftar database
\c DB -- koneksi ke DB
\dt[+] [schema.]pat -- daftar tabel
\dv[+] -- daftar tampilan
\ds[+] -- daftar urutan
\df[+] [pat] -- daftar fungsi
\d[S+] name -- deskripsikan tabel/tampilan/urutan
\dn[+] -- daftar skema
\du[+] -- daftar peran
\timing -- aktifkan/matikan tampilan waktu query
\x -- tampilan diperluas
\e -- edit buffer di $EDITOR
\i file.sql -- jalankan file
\copy ... -- COPY di sisi klien
\! shell_cmd -- jalankan perintah shell
Tipe Data (umum)
- Numerik:
smallint
,integer
,bigint
,decimal(p,s)
,numeric
,real
,double precision
,serial
,bigserial
- Teks:
text
,varchar(n)
,char(n)
- Boolean:
boolean
- Temporal:
timestamp [dengan/tanpa zona waktu]
,date
,time
,interval
- UUID:
uuid
- JSON:
json
,jsonb
(direkomendasikan) - Array:
type[]
misalnyatext[]
- Jaringan:
inet
,cidr
,macaddr
- Geometri:
point
,line
,polygon
, dll.
Periksa versi PostgreSQL
SELECT version();
Versi Server PostgreSQL:
pg_config --version
Versi Klien PostgreSQL:
psql --version
DDL (Buat / Ubah)
-- Buat skema & tabel
CREATE SCHEMA IF NOT EXISTS app;
CREATE TABLE app.users (
id bigserial PRIMARY KEY,
email text NOT NULL UNIQUE,
name text,
active boolean NOT NULL DEFAULT true,
created_at timestamptz NOT NULL DEFAULT now(),
profile jsonb,
tags text[]
);
-- Ubah
ALTER TABLE app.users ADD COLUMN last_login timestamptz;
ALTER TABLE app.users ALTER COLUMN name SET NOT NULL;
ALTER TABLE app.users DROP COLUMN tags;
-- Keterbatasan
ALTER TABLE app.users ADD CONSTRAINT email_lower_uk UNIQUE (lower(email));
-- Indeks
CREATE INDEX ON app.users (email);
CREATE UNIQUE INDEX CONCURRENTLY users_email_uidx ON app.users (lower(email));
CREATE INDEX users_profile_gin ON app.users USING gin (profile);
CREATE INDEX users_created_at_idx ON app.users (created_at DESC);
DML (Sisipkan / Perbarui / Upsert / Hapus)
INSERT INTO app.users (email, name) VALUES
('a@x.com','A'), ('b@x.com','B')
RETURNING id;
-- Upsert (ON CONFLICT)
INSERT INTO app.users (email, name)
VALUES ('a@x.com','Alice')
ON CONFLICT (email)
DO UPDATE SET name = EXCLUDED.name, updated_at = now();
UPDATE app.users SET active = false WHERE last_login < now() - interval '1 tahun';
DELETE FROM app.users WHERE active = false AND last_login IS NULL;
Dasar Pemanggilan Query
SELECT * FROM app.users ORDER BY created_at DESC LIMIT 20 OFFSET 40; -- paginasi
-- Penyaringan
SELECT * FROM app.users WHERE email ILIKE '%@example.%' AND active;
-- Agregat & GROUP BY
SELECT active, count(*) AS n
FROM app.users
GROUP BY active
HAVING count(*) > 10;
-- Join
SELECT o.id, u.email, o.total
FROM app.orders o
JOIN app.users u ON u.id = o.user_id
LEFT JOIN app.discounts d ON d.id = o.discount_id;
-- DISTINCT ON (spesifik PostgreSQL)
SELECT DISTINCT ON (user_id) user_id, status, created_at
FROM app.events
ORDER BY user_id, created_at DESC;
-- CTE
WITH recent AS (
SELECT * FROM app.orders WHERE created_at > now() - interval '30 hari'
)
SELECT count(*) FROM recent;
-- CTE Rekursif
WITH RECURSIVE t(n) AS (
SELECT 1
UNION ALL
SELECT n+1 FROM t WHERE n < 10
)
SELECT sum(n) FROM t;
Fungsi Jendela
SELECT
user_id,
created_at,
sum(total) OVER (PARTITION BY user_id ORDER BY created_at) AS running_total,
row_number() OVER (PARTITION BY user_id ORDER BY created_at) AS rn,
lag(total, 1) OVER (PARTITION BY user_id ORDER BY created_at) AS prev_total
FROM app.orders;
JSON / JSONB
-- Ekstraksi
SELECT profile->>'company' AS company FROM app.users;
SELECT profile->'address'->>'city' FROM app.users;
-- Indeks untuk query jsonb
CREATE INDEX users_profile_company_gin ON app.users USING gin ((profile->>'company'));
-- Keberadaan / kandungan
SELECT * FROM app.users WHERE profile ? 'company'; -- kunci ada
SELECT * FROM app.users WHERE profile @> '{"role":"admin"}'; -- mengandung
-- Perbarui jsonb
UPDATE app.users
SET profile = jsonb_set(COALESCE(profile,'{}'::jsonb), '{prefs,theme}', '"dark"', true);
Array
-- keanggotaan & kandungan
SELECT * FROM app.users WHERE 'vip' = ANY(tags);
SELECT * FROM app.users WHERE tags @> ARRAY['beta'];
-- tambahkan
UPDATE app.users SET tags = array_distinct(tags || ARRAY['vip']);
Waktu & Tanggal
SELECT now() AT TIME ZONE 'Australia/Melbourne';
SELECT date_trunc('day', created_at) AS d, count(*)
FROM app.users GROUP BY d ORDER BY d;
-- Interval
SELECT now() - interval '7 hari';
Transaksi & Kunci
BEGIN;
UPDATE app.accounts SET balance = balance - 100 WHERE id = 1;
UPDATE app.accounts SET balance = balance + 100 WHERE id = 2;
COMMIT; -- atau ROLLBACK
-- Tingkat isolasi
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
-- Periksa kunci
SELECT * FROM pg_locks l JOIN pg_stat_activity a USING (pid);
Peran & Hak Akses
-- Buat peran/pengguna
CREATE ROLE app_user LOGIN PASSWORD 'secret';
GRANT USAGE ON SCHEMA app TO app_user;
GRANT SELECT, INSERT, UPDATE, DELETE ON ALL TABLES IN SCHEMA app TO app_user;
ALTER DEFAULT PRIVILEGES IN SCHEMA app GRANT SELECT, INSERT, UPDATE, DELETE ON TABLES TO app_user;
Impor / Ekspor
-- Sisi server (memerlukan superuser atau izin yang tepat)
COPY app.users TO '/tmp/users.csv' CSV HEADER;
COPY app.users(email,name) FROM '/tmp/users.csv' CSV HEADER;
-- Sisi klien (psql)
\copy app.users TO 'users.csv' CSV HEADER
\copy app.users(email,name) FROM 'users.csv' CSV HEADER
Kinerja & Observabilitas
EXPLAIN (ANALYZE, BUFFERS, VERBOSE) SELECT ...; -- waktu runtime aktual
-- Tampilan statistik
SELECT * FROM pg_stat_user_tables;
SELECT * FROM pg_stat_statements ORDER BY total_time DESC LIMIT 20; -- memerlukan ekstensi
-- Pemeliharaan
VACUUM [FULL] [VERBOSE] table_name;
ANALYZE table_name;
REINDEX TABLE table_name;
Aktifkan ekstensi yang diperlukan:
CREATE EXTENSION IF NOT EXISTS pg_stat_statements;
CREATE EXTENSION IF NOT EXISTS btree_gin;
CREATE EXTENSION IF NOT EXISTS pg_trgm; -- pencarian trigram
Pencarian Teks Penuh (cepat)
ALTER TABLE app.docs ADD COLUMN tsv tsvector;
UPDATE app.docs SET tsv = to_tsvector('english', coalesce(title,'') || ' ' || coalesce(body,''));
CREATE INDEX docs_tsv_idx ON app.docs USING gin(tsv);
SELECT id FROM app.docs WHERE tsv @@ plainto_tsquery('english', 'quick brown fox');
Pengaturan psql yang Berguna
\pset pager off -- nonaktifkan pager
\pset null '∅'
\pset format aligned -- lainnya: unaligned, csv
\set ON_ERROR_STOP on
\timing on
Query Katalog yang Berguna
-- Ukuran tabel
SELECT relname, pg_size_pretty(pg_total_relation_size(relid)) AS size
FROM pg_catalog.pg_statio_user_tables ORDER BY pg_total_relation_size(relid) DESC;
-- Bloat indeks (aproksimasi)
SELECT schemaname, relname, indexrelname, idx_scan
FROM pg_stat_user_indexes ORDER BY idx_scan ASC NULLS FIRST LIMIT 20;
Cadangan / Pemulihan
# Cadangan logis
pg_dump -h HOST -U USER -d DB -F c -f db.dump # format custom
pg_restore -h HOST -U USER -d NEW_DB -j 4 db.dump
# SQL biasa
pg_dump -h HOST -U USER -d DB > dump.sql
psql -h HOST -U USER -d DB -f dump.sql
Replikasi (tingkat tinggi)
- File WAL mengalir dari utama → standby
- Pengaturan kunci:
wal_level
,max_wal_senders
,hot_standby
,primary_conninfo
- Alat:
pg_basebackup
,standby.signal
(PG ≥12)
Hal-hal yang Perlu Diperhatikan & Tips
- Selalu gunakan
jsonb
, bukanjson
, untuk indeks dan operator. - Preferensi
timestamptz
(timezone-aware). DISTINCT ON
adalah emas PostgreSQL untuk “top-N per group”.- Gunakan
GENERATED ALWAYS AS IDENTITY
alih-alihserial
. - Hindari
SELECT *
dalam query produksi. - Buat indeks untuk filter selektif dan kunci join.
- Ukur dengan
EXPLAIN (ANALYZE)
sebelum mengoptimalkan.
Kebijakan Versi Tertentu (≥v12+)
-- Identitas yang dihasilkan
CREATE TABLE t (id bigINT GENERATED ALWAYS AS IDENTITY, . ..);
-- UPSERT dengan indeks parsial
CREATE UNIQUE INDEX ON t (key) WHERE is_active;