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Aggregates that have to do full table scans are notoriously slow in Postgres due to how multi-version concurrency control is implemented. Any time you comment
by johnzabroski 15y ago
Aggregates that have to do full table scans are notoriously slow in Postgres due to how multi-version concurrency control is implemented.
Any time you comment out a WHERE clause on a big table while performing an aggregate report, Postgres chokes.
- gtuhl 15y agoCompared to MyISAM? Sure for certain aggregate functions, but it's too easy to point out reasons for avoiding MyISAM: fragmentation, no transactions, table locks on writes, complete table rewrites to change columns or indexes, only scales up to about 8 cores. Compared to InnoDB? You are incorrect, Postgres is faster, even for a raw count(*), even when comparing against the InnoDB plugin and not the ancient InnoDB builtin. I have access to tuned TB+ DBs of both types and am happy to disprove any specific examples you can provide.
- johnzabroski 15y agoI just read up on this and it appears you are right, my issues are fixed in more recent versions of PostgreSQL. Apologies.