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.

logo postgresql

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[] misalnya text[]
  • 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 utamastandby
  • 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, bukan json, untuk indeks dan operator.
  • Preferensi timestamptz (timezone-aware).
  • DISTINCT ON adalah emas PostgreSQL untuk “top-N per group”.
  • Gunakan GENERATED ALWAYS AS IDENTITY alih-alih serial.
  • 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;

Tautan yang Berguna