Postgresql

PostgreSQL 16+ Reference

Version: 16+. All syntax is standard; most features apply to PostgreSQL 13+.

Quick patterns

-- Check running queries
SELECT pid, state, wait_event_type, query FROM pg_stat_activity WHERE state != 'idle';

-- Explain a slow query
EXPLAIN (ANALYZE, BUFFERS, FORMAT TEXT) SELECT ...;

-- List table sizes
SELECT relname, pg_size_pretty(pg_total_relation_size(oid)) FROM pg_class
WHERE relkind = 'r' ORDER BY pg_total_relation_size(oid) DESC;

-- Kill a blocking query
SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE pid = ;

Key non-obvious facts

• Every statement runs in a transaction. Without BEGIN, each statement auto-commits.
• jsonb stores parsed binary (faster queries); json stores raw text (exact input preserved). Prefer jsonb.
• LIKE 'foo%' can use B-tree; LIKE '%foo' cannot — use pg_trgm GIN for suffix search.
• CREATE INDEX CONCURRENTLY avoids table lock but cannot run inside a transaction block.
• EXPLAIN without ANALYZE shows the planner's estimate. Always use EXPLAIN (ANALYZE, BUFFERS) for real data.
• Null values are stored in indexes by B-tree (unlike some other databases). IS NULL can use an index.
• SERIAL/BIGSERIAL are shorthand for sequence + default; prefer GENERATED ALWAYS AS IDENTITY (SQL standard).
• Default isolation level is Read Committed. SERIALIZABLE prevents all anomalies but may abort transactions.

Reference files

Load the relevant file when working on a specific topic:

| Topic | File | When to read | | -------------------------------------- | -------------------------------------------------------- | -------------------------------------- | | SELECT, JOINs, CTEs, window functions | [references/queries.md](references/queries.md) | Writing or debugging any query | | CREATE TABLE, ALTER TABLE, constraints | [references/ddl-schema.md](references/ddl-schema.md) | Designing or modifying schemas | | Index types, creation, strategy | [references/indexes.md](references/indexes.md) | Adding indexes or fixing slow queries | | Transactions, savepoints, isolation | [references/transactions.md](references/transactions.md) | Concurrency, locking, isolation issues | | JSONB operators, GIN, jsonpath | [references/jsonb.md](references/jsonb.md) | Working with JSON/JSONB columns | | EXPLAIN output, VACUUM, stats | [references/performance.md](references/performance.md) | Query tuning or performance analysis | | psql meta-commands | [references/psql-cli.md](references/psql-cli.md) | Working interactively in psql |

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: jgamaraalv
• Source: jgamaraalv/ts-dev-kit
• License: MIT

Install and usage instructions live in the source repository linked above.