3 ms·

Yeah. It's odd that you got down-voted for this comment. "ORDER BY random() LIMIT 10" is known to be slow on large tables. The correct way to do get a random sa

Yeah. It's odd that you got down-voted for this comment. "ORDER BY random() LIMIT 10" is known to be slow on large tables. The correct way to do get a random sample is to use "SELECT ... FROM table TABLESAMPLE SYSTEM (10)" https://www.postgresql.org/docs/current/sql-select.html#SQL-FROM https://www.postgresql.org/docs/current/sql-select.html#SQL-... You can even use a repeatable seed with this method.

tmoertel 3y ago
Note that TABLESAMPLE SYSTEM is not guaranteed to give you a uniform sample, as it samples blocks, whereas ORDER BY RANDOM() LIMIT samples uniformly distributed rows. Some database systems support TABLESAMPLE RESERVOIR to guarantee uniform sampling behavior.