Essential PostgreSQL Queries Every Data Engineer Should Know 🚀
As a Data Engineer, mastering PostgreSQL queries can help you optimize database performance and troubleshoot issues efficiently. Here are some essential queries to keep in your toolkit! 🛠️
1️⃣ Check Tablespace Size
Monitor the disk space used by your tablespaces:
SELECT spcname AS tablespace, pg_size_pretty(pg_tablespace_size(spcname))
FROM pg_tablespace;
2️⃣ Find Active Sessions
Identify currently active database connections:
SELECT pid, usename, application_name, state, query
FROM pg_stat_activity
WHERE state = ‘active’;
3️⃣ Identify Blocking Queries
Find queries that are blocking other transactions:
SELECT pid, age(clock_timestamp(), query_start) AS duration, usename, state, query
FROM pg_stat_activity
WHERE waiting;
4️⃣ Check CPU Usage of Queries
Analyze database CPU usage:
SELECT datname, pid, usename, application_name, client_addr, state,
round(extract(epoch FROM (now() – query_start))::numeric, 2) AS runtime_seconds,
query
FROM pg_stat_activity
ORDER BY runtime_seconds DESC;
5️⃣ Monitor Slow Queries
Retrieve the slowest queries using pg_stat_statements:
SELECT query, calls, total_time, mean_time
FROM pg_stat_statements
ORDER BY total_time DESC LIMIT 5;
6️⃣ List Unused Indexes
Identify indexes that are not being used frequently:
SELECT schemaname, relname AS table_name, indexrelname AS index_name, idx_scan
FROM pg_stat_user_indexes
WHERE idx_scan = 0;
7️⃣ Check Database Size
View the size of each database:
SELECT datname, pg_size_pretty(pg_database_size(datname)) AS size
FROM pg_database;
8️⃣ View Cache Hit Ratio
Measure how efficiently PostgreSQL is using cache:
SELECT sum(blks_hit) / (sum(blks_hit) + sum(blks_read)) AS cache_hit_ratio
FROM pg_stat_database;
Mastering these PostgreSQL queries will make you a more efficient Data Engineer! 🚀
What’s your go-to PostgreSQL query? Drop it in the comments! 👇