replace msg_store:attrs with contains

This is a step on the path to getting rid of message attributes in msg_store.

msg_store:attrs was only being used in disk_queue:prune, to detect
when the store contained a non-persistent message and remove that
message from the store and the rabbit_disk_queue table.

Now rabbit_disk_queue records contain an IsPersistent flag. By making
the msg count delta generator pay attention to that flag we trim
non-persistent messages from the store during its initialisation,
disk_queue:prune no longer needs to remove messages from the store, it
just needs to remove all messages from the rabbit_disk_queue table
which are no longer referenced by the store - hence the new
msg_store:contains function.

Keeping the IsPersistent flag in the rabbit_disk_queue table is
sub-optimal since it means we store it once per message reference
rather than just once per message. That's a small price to pay though
for the cleaner interaction between the disk_queue and msg_store, and
the opportunity to remove the notion of message attributes from
msg_store altogether.

Populating the new field in rabbit_disk_queue is straightforward in
most places except disk_queue:tx_commit. That used to just be given
{MsgId, IsDelivered} tuples, so I had to change the API to {MsgId,
IsDelivered, IsPersistent} tuples.

1 files changed, 1 insertions, 1 deletions

diff --git a/include/rabbit.hrl b/include/rabbit.hrl
index 095044e797..bebaee98f6 100644
--- a/include/rabbit.hrl
+++ b/include/rabbit.hrl
@@ -65,7 +65,7 @@
 -record(basic_message, {exchange_name, routing_key, content,
                         guid, is_persistent}).
 
--record(dq_msg_loc, {queue_and_seq_id, is_delivered, msg_id}).
+-record(dq_msg_loc, {queue_and_seq_id, is_delivered, is_persistent, msg_id}).
 
 -record(ssl_socket, {tcp, ssl}).
 -record(delivery, {mandatory, immediate, txn, sender, message}).