Today, I was looking for a quick way to see HTTP response codes of a bunch of urls. Naturally, I turned to the curl command, which I would usually use like this:

curl -IL "URL"

This command would send a HEAD request (-I), follow through all redirects (-L), and display some useful information in the end. Most of the time it's ideal:

curl -IL "http://www.google.com"
 
HTTP/1.1 200 OK
Date: Fri, 11 Jun 2010 03:58:55 GMT
Expires: -1
Cache-Control: private, max-age=0
Content-Type: text/html; charset=ISO-8859-1
Server: gws
X-XSS-Protection: 1; mode=block
Transfer-Encoding: chunked

However, the server I was curling didn't support HEAD requests explicitly. Additionally, I was really only interested in HTTP status codes and not in the rest of the output. This means I would have to change my strategy and

Here’s something that’s not really documented anywhere (unless you count ha_innodb.cc as a source of server documentation). You may have some idea about the MySQL/Drizzle row buffer format. This is passed around the storage engine interface: in for write_row and update_row and out for the various scan and index read methods.

If you want to see the docs for it that exist in the code, check out store_key_val_for_row in ha_innodb.cc.

However, there is another format that is passed to your engine (and that your engine is expected to understand) and for lack of a better name, I’m going to call it the key tuple format. The first place you’ll probably see this is when implementing the index_read function for a Cursor (or handler in MySQL speak).

You get two things: a pointer to the buffer and the length of the buffer. Since a