Postgresql for OLAP

Question

Does anyone have experience of using PostgreSQL for an OLAP setup, using cubes against the database etc. Having come across a number of idiosyncracies when using MySQL for OLAP, are there reasons in favour of using PostgreSQL instead (assuming that I want to go the open source route)?

Dowery

We are using PostgreSQL 9.1 and Saiku. All cube schemas are defined in Schema Workbench (Pentaho). So far, I do not see any issues with such configuration. We do have fact tables with approx. 1,000,000 rows and all works well without any pre-aggregation. – Abuttal

Answer 1

There are a number of data warehousing software vendors that are based on Postgresql (and contribute OLAP related changes back to core fairly regularly). Check out https://greenplum.org/. You'll find that PG works a lot better (for nearly any workload, OLAP especially) than MySQL. Greenplum and other similar solutions should work a bit better than PG depending on your data sets and use cases.

Thad

Do you mean "Pivotal Greenplum Database" or community version? – Desjardins

Answer 2

PGSQL is much better suited for Data Warehousing compared to MySQL. We had thought initially to go with MySQL, but it performs poorly in aggregations if data grows to a few million rows. PGSQL performs almost 20 times faster in caparison with MySQL for 20 million records for a single fact table on same hardware setup. If for some reason you choose to go with MySQL, then you should use MyISAM storage engine for fact tables rather then InnoDB; you will see slightly better performance.

Avilla

Just a note. AFAIK, MyISAM engine does not support ACID transactions. Large size dataset is very likely to be broken like PostgreSQL which is always ACID transactional. – Forth

ACID is mostly irrelevant in OLAP systems because they are read-only environments, with the exception of SCDs. The ETL process must ensure data integrity. This assumes you have implemented a star schema and Kimball's enterprise DW bus architecture. – Chancellorship