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0 pointshuggyface14y ago0 comments

MySQL had some historic issues with schema changes -- adding a column to a table with a few million records could take hours. While it does have a lot of work to do -- it is restructuring every page of the database -- in competitive products such a change takes a minute fraction of the time (limited only by IO performance).

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gizzlon14y ago

But altering a table would still block it? And possible even other tables as well? And take a long time?

Only ever done this in MySQL, where you really can't alter big, live, tables. Well, facebook made an utility for it: http://www.facebook.com/notes/mysql-at-facebook/online-schem...

jeltz14y ago

Most changes would still block, yes, but at least in PostgreSQL many changes will only block a short time (since they do not require a full table rewrite, only altering the table descirption) and in my experience rewriting a table is generally quick for a decent sized database (tables with a handful of millions of rows).

jcromartie14y ago

I see. That makes much more sense. Yes, I suppose I'm used to DB servers that are more nimble in that department.

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