[tarantool-patches] Re: [PATCH v2 2/7] vinyl: don't exempt dropped indexes from dump and compaction
Vladimir Davydov
vdavydov.dev at gmail.com
Tue Aug 20 12:02:12 MSK 2019
On Tue, Aug 20, 2019 at 11:12:27AM +0300, Vladimir Davydov wrote:
> On Mon, Aug 19, 2019 at 11:47:00PM +0300, Konstantin Osipov wrote:
> > * Vladimir Davydov <vdavydov.dev at gmail.com> [19/08/19 19:57]:
> > > vy_lsm_read_set_t read_set;
> > > + /**
> > > + * Triggers run when the last reference to this LSM tree
> > > + * is dropped and the LSM tree is about to be destroyed.
> > > + * A pointer to this LSM tree is passed to the trigger
> > > + * callback in the 'event' argument.
> > > + */
> > > + struct rlist on_destroy;
> >
> > Please explain in the comment that the compaction scheduler task takes a
> > reference as well, so if the dropped index happens to be compacted
> > at the moment, it will be dropped only when the compaction task
> > finishes.
>
> True. We could avoid that, but for now it isn't worth bothering about
> IMO. I'll add a comment.
Here goes the comment:
diff --git a/src/box/vy_lsm.h b/src/box/vy_lsm.h
index 47f8ee6a..3b553ea5 100644
--- a/src/box/vy_lsm.h
+++ b/src/box/vy_lsm.h
@@ -317,6 +317,13 @@ struct vy_lsm {
* is dropped and the LSM tree is about to be destroyed.
* A pointer to this LSM tree is passed to the trigger
* callback in the 'event' argument.
+ *
+ * For instance, this trigger is used to remove a dropped
+ * LSM tree from the scheduler before it gets destroyed.
+ * Since each dump/compaction task takes a reference to
+ * the target index, this means that a dropped index will
+ * not get destroyed until all tasks scheduled for it have
+ * been completed.
*/
struct rlist on_destroy;
};
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