[#997] Evolutions splitting fix (Play 2.0 version)

[Wilhansen]

The same fix for https://play.lighthouseapp.com/projects/57987-play-framework/tickets/997 "ported" to Play 2.0 (but still Java version). Note that the main code is now located in play.core.utils instead of play.db as in Play 1.2.x

[fcanedo]

I see this tries to split the SQL statements properly. However, is there a specific reason why they should be split at all? Can't we just send the whole thing in one Statement?

[Wilhansen]

Actually, that's what I thought too: http://groups.google.com/group/play-framework/browse_frm/thread/72de8ed20c552568/6c76c5443b50e6d5?lnk=gst&q=sql+split#6c76c5443b50e6d5
this is also how we temporarily fixed this issue with our app running on PostgreSQL (by just sending the entire thing).

But apparently (or rather, probably as I haven't emperically tested it), different DBs have different behaviors. Some might probably disallow it to prevent SQL-injection attacks (since you can't run more than 2 statements per exec).

[fcanedo]

That's unfortunate, if that's the case. So far, I've tested with postrgresql and H2; they're both fine with multiple SQL statements in one execute(). I guess it all depends on how the driver developers interpret the API docs: http://docs.oracle.com/javase/6/docs/api/java/sql/Statement.html#execute(java.lang.String)

Can "an unknown SQL string" be interpreted as a string with one or more SQL statements and have they? None of the relevant documentation that I could find makes it clear what's supposed to be allowed. I do think, though, that having this limited to one statement, seems a bit artificial.

[Wilhansen]

I'm not a MySQL user but it seems that the MySQL JDBC driver will have problems accepting multiple statements per exec unless you set "allowMultiQueries=true" in the connection string: http://dev.mysql.com/doc/refman/5.6/en/connector-j-reference-configuration-properties.html and some people say they placed the limitation to minimize SQL injection attacks...

OT: sorry again for screwing up the pull request.... just cherry pick the first and last commit if ever. (I still need to get a hang of this)

[fcanedo]

Like I said, unfortunate :(

But, I've tested your splitter with the use-case that I ran into this problem with and it works.

Thanks for the fix.

[guillaumebort]

I'm going to fix this, but we have to find a really good solution for that. And to write a good parser.

[adamhooper]

Is there another bug filed somewhere on this issue? I can't find one, aside from http://play.lighthouseapp.com/projects/82401/tickets/212 which is marked as a duplicate of some as-yet-unnamed bug....

My 2p: since what's valid SQL changes from RDBMS to RDBMS, shouldn't Play use RDBMS-specific logic? That might take less effort than writing a good parser, because many RDBMSs allow sending the entire evolution in one Statement.