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/** @page tut_mongo_sync_query Querying documents
*
* We can connect, insert, and we still vaguely remember how to build
* BSON objects: how about we go out and query the database this time?
*
* @dontinclude tut_mongo_sync.c
* @skip tut_sync_insert
* @skip }
* @skip void
* @until {
*
* First, we define a couple of variables: a connection, a packet, a
* cursor, a BSON object and a counter:
*
* @until gint i
*
* We'll use the packet as an intermediate step between querying and
* making a cursor. We'll see why later. The query will be used to
* limit the documents queried, and the counter is just for pretty
* printing.
*
* Then we do our routine connect:
* @until }
*
* And then build a BSON object, an empty one, because an empty query
* means we're interested in all of the documents!
* @until bson_finish
*
* Now we have a connection, and we have a query, lets tell MongoDB
* what we want:
*
* @until bson_free
*
* The first two parameters are obvious. The third is a set of flags -
* but we don't use any right now. Then comes the number of documents
* to skip, and the number of documents to return, followed by a
* query, and an optional field selector, which we just left empty
* (meaning we want all fields returned).
*
* There's more than one way to figure out the data returned by a
* query: we can either use the returned packet as-is, and extract
* data from it using the low-level mongo_wire family of functions. Or
* we can make a cursor out of this packet, and iterate over the
* elements:
*
* @until }
*
* @until }
*
* The first thing we do inside of the loop is to get the data from
* the cursor - or bail out with an error if we can't.
*
* @until printf
*
* Then we proceed to make a BSON cursor, and print all the keys that
* belong to the document.
*
* Once that's done, we free the resources we used, and continue along
* the loop, until our cursor signals the end of the query.
*
* @until printf
*
* @until }
*
* Then we clean up and go home:
* @until }
*/
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