[Tarantool-patches] [PATCH 14/15] tx: introduce point conflict tracker

[Aleksandr Lyapunov <alyapunov@tarantool.org>]

---
 src/box/txn.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 src/box/txn.h |  4 +++
 2 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/src/box/txn.c b/src/box/txn.c
index 26377c6..f1a7785 100644
--- a/src/box/txn.c
+++ b/src/box/txn.c
@@ -75,6 +75,13 @@ struct tx_manager
 /** The one and only instance of tx_manager. */
 static struct tx_manager txm;
 
+struct tx_read_tracker {
+	struct txn *reader;
+	struct txm_story *story;
+	struct rlist in_reader_list;
+	struct rlist in_read_set;
+};
+
 struct tx_conflict_tracker {
 	struct txn *wreaker;
 	struct txn *victim;
@@ -237,6 +244,7 @@ txn_new(void)
 	}
 	assert(region_used(&region) == sizeof(*txn));
 	txn->region = region;
+	rlist_create(&txn->read_set);
 	rlist_create(&txn->conflict_list);
 	rlist_create(&txn->conflicted_by_list);
 	return txn;
@@ -248,6 +256,14 @@ txn_new(void)
 inline static void
 txn_free(struct txn *txn)
 {
+	struct tx_read_tracker *tracker, *tmp;
+	rlist_foreach_entry_safe(tracker, &txn->read_set,
+				 in_read_set, tmp) {
+		rlist_del(&tracker->in_reader_list);
+		rlist_del(&tracker->in_read_set);
+	}
+	assert(rlist_empty(&txn->read_set));
+
 	struct tx_conflict_tracker *entry, *next;
 	rlist_foreach_entry_safe(entry, &txn->conflict_list,
 				 in_conflict_list, next) {
@@ -654,7 +670,6 @@ txn_prepare(struct txn *txn)
 		rlist_del(&entry->in_conflicted_by_list);
 	}
 
-
 	trigger_clear(&txn->fiber_on_stop);
 	if (!txn_has_flag(txn, TXN_CAN_YIELD))
 		trigger_clear(&txn->fiber_on_yield);
@@ -1585,3 +1600,71 @@ txm_story_delete(struct txm_story *story)
 	struct mempool *pool = &txm.txm_story_pool[story->index_count];
 	mempool_free(pool, story);
 }
+
+int
+tx_track_read(struct txn *txn, struct tuple *tuple, uint32_t index_count)
+{
+	if (tuple == NULL)
+		return 0;
+	if (txn == NULL)
+		return 0;
+
+	struct txm_story *story;
+	struct tx_read_tracker *tracker = NULL;
+
+	if (!tuple->is_dirty) {
+		story = txm_story_new(tuple, NULL, index_count);
+		if (story != NULL)
+			return -1;
+		size_t sz;
+		tracker = region_alloc_object(&txn->region,
+		                              struct tx_read_tracker, &sz);
+		if (tracker == NULL) {
+			diag_set(OutOfMemory, sz, "tx region", "read_tracker");
+			txm_story_delete(story);
+			return -1;
+		}
+		tracker->reader = txn;
+		tracker->story = story;
+		rlist_add(&story->reader_list, &tracker->in_reader_list);
+		rlist_add(&txn->read_set, &tracker->in_read_set);
+		return 0;
+	}
+	story = txm_story_get(tuple);
+
+	struct rlist *r1 = story->reader_list.next;
+	struct rlist *r2 = txn->read_set.next;
+	while (r1 != &story->reader_list && r2 != &txn->read_set) {
+		tracker = rlist_entry(r1, struct tx_read_tracker,
+				      in_reader_list);
+		assert(tracker->story == story);
+		if (tracker->reader == txn)
+			break;
+		tracker = rlist_entry(r2, struct tx_read_tracker,
+				      in_read_set);
+		assert(tracker->reader == txn);
+		if (tracker->story == story)
+			break;
+		tracker = NULL;
+		r1 = r1->next;
+		r2 = r2->next;
+	}
+	if (tracker != NULL) {
+		/* Move to the beginning of a list for faster further lookups.*/
+		rlist_del(&tracker->in_reader_list);
+		rlist_del(&tracker->in_read_set);
+	} else {
+		size_t sz;
+		tracker = region_alloc_object(&txn->region,
+					      struct tx_read_tracker, &sz);
+		if (tracker == NULL) {
+			diag_set(OutOfMemory, sz, "tx region", "read_tracker");
+			return -1;
+		}
+		tracker->reader = txn;
+		tracker->story = story;
+	}
+	rlist_add(&story->reader_list, &tracker->in_reader_list);
+	rlist_add(&txn->read_set, &tracker->in_read_set);
+	return 0;
+}
diff --git a/src/box/txn.h b/src/box/txn.h
index b5eda1e..4567f2c 100644
--- a/src/box/txn.h
+++ b/src/box/txn.h
@@ -293,6 +293,7 @@ struct txn {
 	uint32_t fk_deferred_count;
 	/** List of savepoints to find savepoint by name. */
 	struct rlist savepoints;
+	struct rlist read_set;
 	struct rlist conflict_list;
 	struct rlist conflicted_by_list;
 };
@@ -781,6 +782,9 @@ txm_tuple_clarify(struct txn *txn, struct tuple* tuple, uint32_t index,
 void
 txm_story_delete(struct txm_story *story);
 
+int
+tx_track_read(struct txn *txn, struct tuple *tuple, uint32_t index_count);
+
 #if defined(__cplusplus)
 } /* extern "C" */
 #endif /* defined(__cplusplus) */
-- 
2.7.4