Make server_status available

[cdegroot]

This patch sets server_status in MySql2::Client whenever it's relevant. These flags contain important information about how the server viewed the query; it's useful to log this (or even throw errors ;-)) during development so slow queries can be prevented from reaching production.

First patch, first time I'm doing Ruby extensions, so flame away. If the code is good in principle, I'll look into adding some test coverage.

[sodabrew]

Thanks, I need to do a bit of reading since the MYSQL structure is semi-opaque per http://dev.mysql.com/doc/refman/5.7/en/c-api-data-structures.html -- I think we reach into it in just one other place.

Would you also take a look at the spec/ directory to add a test?

[cdegroot]

If you look positively at this patch, I'm absolutely going to be creative and add a test, no worries :-). We have a long weekend up here in Canada, will whip something up on Tuesday.

[sodabrew]

Thinking some more about this, it might make sense to break these out as separate true/false properties of the Result object rather than the Client object.

[cdegroot]

Either works for me - your call. The reason I took this approach is mainly that it stays "in the same object" as the MySQL C client, and it just sets a single value minimizing overhead - I have no idea how many instructions are involved in setting Ruby properties from C, so I wanted to stay on the safe side.

[cdegroot]

Update: moved to three individual flags in a @server_flags hash and added a quick test.

[sodabrew]

This function is only called from within client.c, so you can make it static and leave it out of the header file.

[sodabrew]

Oh, it's also called from statement.c, sorry. Since the function name is exposed in the shared module, please prefix the function name - something like rb_mysql_set_result_server_flags, and move it up a bit, so it's under the rb_mysql_client_set_active_thread definition.

[sodabrew]

I like the second version a lot! Just a nit about the function name.

I have half an idea to add accessors like these:

Mysql2::Result#no_index_used?
Mysql2::Result#no_good_index_used?
Mysql2::Result#query_was_slow?

The test failures are unrelated, I will look into those as I have time. Your new test passes.

[cdegroot]

(Updated function name and location in header file)

[sodabrew]

Could you add these symbols as static VALUEs at the top of the file and in the module init? You should see a laundry list of sym_foo values initialized around line 1350.

[sodabrew]

Merged as 811a57a