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Comment by bsg75 | Hacker News Reader

> MongoDB is easy to make fun of.

I think more often its easy to poke fun at _how_ its used.

When any tool or tech is used globally, before knowing its limitations, problems are likely. Attempting to use MongoDB in all storage or persistence scenarios is no more sensible than using MySQL in all cases.

Yes, there is marketing around this product that must be looked at critically - after taking into account that many newly developed technologies won't solve all the problems older tech have worked for decades to solve.

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> Attempting to use MongoDB in all storage or persistence scenarios is no more sensible than using MySQL in all cases.

Substantially less sensible in many cases. MySQL has its issues (it has a lot of issues), but people have been able to get it to work surprisingly well in roles that it wasn't designed for (albeit sometimes by just building a database on top of it, as with Twitter's thing).

MySQL fills the "networked reliable transnational BTrees on disk" niche fairly well.

I think the difference is you don't get made fun of online for using MySQL for everything

MySQL is richly deserving of ridicule as well. It's ubiquity is unfortunate.

If you're going to comment so strongly, some explanation of why it deserves such ridicule would contribute much more value to the discussion.

No check constraints. Spotty transaction isolation. Silent data corruption if you happen to make certain kinds of updates while using statement-based replication. No on-line schema updates (is that still true?). Complete inability to execute joins of any size in reasonable time due to the lack of merge or hash join strategies. Corresponding inability to handle subqueries of any complexity. Readers block writers (at table level with MyISAM - and still at row level with InnoDB?).

As well as things like that which are actually ridiculous, there is also the substantial gap in features as compared to real databases. Things like recursive queries, user-defined types, partial indices, etc, are commonplace in the more sophisticated databases. You probably won't need them for a simple web application (or even a complex one!), but they can be very useful when trying to do more complex things, or manage a complex system efficiently.

Besides the corruption, that just sounds like it's missing features. Missing features is ridicule worthy?

It can be when you look at how long people have been asking for these things.

When the "feature" is a basic property of a relational database - as check constraints and efficient joins and subqueries are - then yes.

I believe that InnoDB is an MVCC implementation, so readers blocking writes shouldn't happen. Another thing to add to your list is missing window functions.

I'm not a big MySQL fan at all, but it's still leaps and bounds ahead of mongo technologically.

Readers blocking writes may have been changed in a never version than what we use, but it still exist in at least some versions of 5.x.

My apologies - you're right. In the general case readers don't block writes, but InnoDB does use share locks on some foreign key interactions and when using the SERIALIZABLE isolation level.

Just ran into this link, which seems to describe how MVCC can sometimes not be enough.

http://ronaldbradford.com/blog/understanding-innodb-mvcc-200...

Having read through it, I rather suspect that that's not a matter of writers blocking readers or the other way round, but instead a case of writers blocking writers - he's writing a lot of data to the table, and it's highly likely that InnoDB has escalated the lock to a table lock - which effectively prevents concurrent writes.

I don't believe that InnoDB escalates locks. Quoting from the fine manual:

http://dev.mysql.com/doc/refman/5.7/en/innodb-transaction-mo...

> InnoDB does locking on the row level and runs queries as nonlocking consistent reads by default, in the style of Oracle. The lock information in InnoDB is stored so space-efficiently that lock escalation is not needed: Typically, several users are permitted to lock every row in InnoDB tables, or any random subset of the rows, without causing InnoDB memory exhaustion.

Nonsense, this is a religious debate. People get made fun of for using MySQL as a regular relational database.

Empathy perhaps.

people make fun of MySQL all the time. especially postgresql people :)

anecdotally in the more than 10 years I've used MySQL I've never had any issues. whereas with postgresql I've had a few major downtime incidents. it can be very stubborn and arcane. but at least I didn't lose any data.

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