Re: Understanding PostgreSQL Storage Engines

At 11:32 AM 10/9/2010, Craig Ringer wrote:
>On 10/09/2010 05:30 AM, Carlos Mennens wrote:
>>I know that MySQL uses MyISAM storage engine by default and was just
>>trying to look on Google to try and see if I could understand what
>>storage engine does PostgreSQL use by default when I generate a
>>database / table. Is there some way someone (me) who knows nothing
>>about how a ORDBMS works understand the difference between all storage
>>engine options and which does PostgreSQL use by default.
>
>In MySQL terms, PostgreSQL's one and only storage engine is much
>more like InnoDB than MyISAM. That's not to say it's particularly
>like MySQL+InnoDB in behaviour, only much *more* like InnoDB than
>MyISAM. It's an MVCC design with proper transaction support (like
>any real database) with minimal locking and a focus on concurrency,
>data integrity and correctness.
>
>If you're used to MySQL, you'll want to read this:
>
> http://wiki.postgresql.org/wiki/Slow_Counting
>
>as it bites MySQL people all the time.

It also affects MySQL users shifting from MyISAM to InnoDB:
http://mysqlha.blogspot.com/2009/08/fast-count-for-innodb.html

So select count isn't always fast on MySQL.

MySQL has a long feature list which is nice for fooling the ignorant.
But you can't use many of them at the same time. Fast count? Use
MyISAM. Full text index? MyISAM. Transactions, use InnoDB. Fast
concurrent inserts, use InnoDB. So on and so forth.

Some call it flexibility and choice... :).

Link.