Contents

• Develoopment Notes
  • Volatility
  • Performances

Develoopment Notes

Volatility

Performances

1. ORDER BY random() : Basic but very slow

SELECT name FROM anon.last_name ORDER BY random() LIMIT 1;

1. OFFSET floor() :

SELECT name FROM anon.last_name OFFSET floor(random()*(SELECT count(*) FROM anon.last_name)) LIMIT 1;                                       

1. TABLESAMPLE

SELECT name FROM @extschema@.last_name TABLESAMPLE SYSTEM(1) LIMIT 1; 

1. tsm-system-rows

SELECT name FROM @extschema@.last_name TABLESAMPLE SYSTEM_ROWS(1);

Links

• https://stackoverflow.com/questions/5297396/quick-random-row-selection-in-postgres/5298588#5298588
• https://blog.2ndquadrant.com/tablesample-in-postgresql-9-5-2/
• http://web.archive.org/web/20080214235745/http://www.powerpostgresql.com/Random_Aggregate
• https://www.postgresql.org/docs/current/static/tsm-system-rows.html