Tablesample In PostgreSQL 9.5

PostgreSQL 9.5 introduces support for TABLESAMPLE, an SQL SELECT clause that returns a random sample from a table. SQL:2003 defines two sampling methods: SYSTEM and BERNOULLI. The SYSTEM method uses random IO whereas BERNOULLI uses sequential IO. SYSTEM is faster, but BERNOULLI gives us a much better random distribution because each tuple (row) has the […]