WT-3207 Don't hold clean handles during checkpoints. (#3319)

Previously, we gathered handles, then started a transaction, then
figured out which handles were clean and released them.  However,
* checkpoints were keeping every handle in both its handle list and in
the meta_tracking list because the *_apply_all functions were saving all
handles when meta_tracking was active; and
* we had acquired exclusive locks on checkpoints to be dropped before
determining that we could skip a checkpoint in a clean tree.  These
locks blocked drops (among other things) until the checkpoint completed.

The solution here is to first start the transaction, then check for
clean handles as checkpoint visits them.  However, this has to cope with
races where a handle changes state in between the transaction starting
and getting the handle (e.g., table creates, bulk loads completing).

1 files changed, 2 insertions, 1 deletions

diff --git a/src/include/txn.i b/src/include/txn.i
index 0cc4a6f8439..314c948e4d1 100644
--- a/src/include/txn.i
+++ b/src/include/txn.i
@@ -125,7 +125,8 @@ __wt_txn_oldest_id(WT_SESSION_IMPL *session)
 	 * minimum of it with the oldest ID, which is what we want.
 	 */
 	oldest_id = txn_global->oldest_id;
-	include_checkpoint_txn = btree == NULL || btree->include_checkpoint_txn;
+	include_checkpoint_txn = btree == NULL ||
+	    btree->checkpoint_gen != txn_global->checkpoint_gen;
 	WT_READ_BARRIER();
 	checkpoint_pinned = txn_global->checkpoint_pinned;