[PATCH v2 1/4] schema: refactor space_cache API

[Kirill Yukhin <kyukhin@tarantool.org>]

Remove function which deletes from cache, making replace
more general: it might be used for both insertions,
deletions and replaces. Also, put assert on equality
of space pointer found in cache to old one into
replace routine.
---
 src/box/alter.cc  | 26 ++++++++++----------------
 src/box/schema.cc | 52 +++++++++++++++++++++++++---------------------------
 src/box/schema.h  |  9 ++-------
 3 files changed, 37 insertions(+), 50 deletions(-)

diff --git a/src/box/alter.cc b/src/box/alter.cc
index de3943c..79ff589 100644
--- a/src/box/alter.cc
+++ b/src/box/alter.cc
@@ -810,9 +810,7 @@ alter_space_rollback(struct trigger *trigger, void * /* event */)
 	 */
 	space_swap_triggers(alter->new_space, alter->old_space);
 	space_swap_fkeys(alter->new_space, alter->old_space);
-	struct space *new_space = space_cache_replace(alter->old_space);
-	assert(new_space == alter->new_space);
-	(void) new_space;
+	space_cache_replace(alter->new_space, alter->old_space);
 	alter_space_delete(alter);
 }
 
@@ -913,9 +911,7 @@ alter_space_do(struct txn *txn, struct alter_space *alter)
 	 * The new space is ready. Time to update the space
 	 * cache with it.
 	 */
-	struct space *old_space = space_cache_replace(alter->new_space);
-	(void) old_space;
-	assert(old_space == alter->old_space);
+	space_cache_replace(alter->old_space, alter->new_space);
 
 	/*
 	 * Install transaction commit/rollback triggers to either
@@ -1421,7 +1417,7 @@ on_drop_space_rollback(struct trigger *trigger, void *event)
 {
 	(void) event;
 	struct space *space = (struct space *)trigger->data;
-	space_cache_replace(space);
+	space_cache_replace(NULL, space);
 }
 
 /**
@@ -1447,9 +1443,7 @@ on_create_space_rollback(struct trigger *trigger, void *event)
 {
 	(void) event;
 	struct space *space = (struct space *)trigger->data;
-	struct space *cached = space_cache_delete(space_id(space));
-	(void) cached;
-	assert(cached == space);
+	space_cache_replace(space, NULL);
 	space_delete(space);
 }
 
@@ -1610,8 +1604,7 @@ on_drop_view_rollback(struct trigger *trigger, void *event)
  *
  * - space cache should be updated, and changes in the space
  *   cache should be reflected in Lua bindings
- *   (this is done in space_cache_replace() and
- *   space_cache_delete())
+ *   (this is done in space_cache_replace())
  *
  * - the space which is changed should be rebuilt according
  *   to the nature of the modification, i.e. indexes added/dropped,
@@ -1695,7 +1688,7 @@ on_replace_dd_space(struct trigger * /* trigger */, void *event)
 		 * cache right away to achieve linearisable
 		 * execution on a replica.
 		 */
-		(void) space_cache_replace(space);
+		(void) space_cache_replace(NULL, space);
 		/*
 		 * Do not forget to update schema_version right after
 		 * inserting the space to the space_cache, since no
@@ -1787,7 +1780,7 @@ on_replace_dd_space(struct trigger * /* trigger */, void *event)
 		 * cache right away to achieve linearisable
 		 * execution on a replica.
 		 */
-		struct space *space = space_cache_delete(space_id(old_space));
+		space_cache_replace(old_space, NULL);
 		/*
 		 * Do not forget to update schema_version right after
 		 * deleting the space from the space_cache, since no
@@ -1795,7 +1788,7 @@ on_replace_dd_space(struct trigger * /* trigger */, void *event)
 		 */
 		++schema_version;
 		struct trigger *on_commit =
-			txn_alter_trigger_new(on_drop_space_commit, space);
+			txn_alter_trigger_new(on_drop_space_commit, old_space);
 		txn_on_commit(txn, on_commit);
 		if (old_space->def->opts.is_view) {
 			struct Select *select =
@@ -1817,7 +1810,8 @@ on_replace_dd_space(struct trigger * /* trigger */, void *event)
 			select_guard.is_active = false;
 		}
 		struct trigger *on_rollback =
-			txn_alter_trigger_new(on_drop_space_rollback, space);
+			txn_alter_trigger_new(on_drop_space_rollback,
+					      old_space);
 		txn_on_rollback(txn, on_rollback);
 	} else { /* UPDATE, REPLACE */
 		assert(old_space != NULL && new_tuple != NULL);
diff --git a/src/box/schema.cc b/src/box/schema.cc
index 2d2be26..08457a46 100644
--- a/src/box/schema.cc
+++ b/src/box/schema.cc
@@ -158,34 +158,33 @@ space_foreach(int (*func)(struct space *sp, void *udata), void *udata)
 	return 0;
 }
 
-/** Delete a space from the space cache and Lua. */
-struct space *
-space_cache_delete(uint32_t id)
-{
-	mh_int_t k = mh_i32ptr_find(spaces, id, NULL);
-	assert(k != mh_end(spaces));
-	struct space *space = (struct space *)mh_i32ptr_node(spaces, k)->val;
-	mh_i32ptr_del(spaces, k, NULL);
-	space_cache_version++;
-	return space;
-}
-
 /**
- * Update the space in the space cache and in Lua. Returns
- * the old space instance, if any, or NULL if it's a new space.
+ * Update the space in the space cache and in Lua.
  */
-struct space *
-space_cache_replace(struct space *space)
+void
+space_cache_replace(struct space *old_space, struct space *new_space)
 {
-	const struct mh_i32ptr_node_t node = { space_id(space), space };
-	struct mh_i32ptr_node_t old, *p_old = &old;
-	mh_int_t k = mh_i32ptr_put(spaces, &node, &p_old, NULL);
-	if (k == mh_end(spaces)) {
-		panic_syserror("Out of memory for the data "
-			       "dictionary cache.");
+	assert(new_space != NULL || old_space != NULL);
+	if (new_space != NULL) {
+		const struct mh_i32ptr_node_t node_p = { space_id(new_space),
+							 new_space };
+		struct mh_i32ptr_node_t old, *p_old = &old;
+		mh_int_t k = mh_i32ptr_put(spaces, &node_p, &p_old, NULL);
+		if (k == mh_end(spaces)) {
+			panic_syserror("Out of memory for the data "
+				       "dictionary cache.");
+		}
+		assert((struct space *)p_old->val == old_space);
+	} else {
+		mh_int_t k = mh_i32ptr_find(spaces, space_id(old_space), NULL);
+		assert(k != mh_end(spaces));
+		struct space *old_space_by_id =
+			(struct space *)mh_i32ptr_node(spaces, k)->val;
+		(void)old_space_by_id;
+		assert(old_space_by_id == old_space);
+		mh_i32ptr_del(spaces, k, NULL);
 	}
 	space_cache_version++;
-	return p_old ? (struct space *) p_old->val : NULL;
 }
 
 /** A wrapper around space_new() for data dictionary spaces. */
@@ -220,7 +219,7 @@ sc_space_new(uint32_t id, const char *name,
 	rlist_create(&key_list);
 	rlist_add_entry(&key_list, index_def, link);
 	struct space *space = space_new_xc(def, &key_list);
-	(void) space_cache_replace(space);
+	(void) space_cache_replace(NULL, space);
 	if (replace_trigger)
 		trigger_add(&space->on_replace, replace_trigger);
 	if (stmt_begin_trigger)
@@ -431,7 +430,7 @@ schema_init()
 		});
 		RLIST_HEAD(key_list);
 		struct space *space = space_new_xc(def, &key_list);
-		space_cache_replace(space);
+		space_cache_replace(NULL, space);
 		init_system_space(space);
 		trigger_run_xc(&on_alter_space, space);
 	}
@@ -447,8 +446,7 @@ schema_free(void)
 
 		struct space *space = (struct space *)
 				mh_i32ptr_node(spaces, i)->val;
-		space_cache_delete(space_id(space));
-		space_delete(space);
+		space_cache_replace(space, NULL);
 	}
 	mh_i32ptr_delete(spaces);
 	while (mh_size(funcs) > 0) {
diff --git a/src/box/schema.h b/src/box/schema.h
index 264c16b..05f32de 100644
--- a/src/box/schema.h
+++ b/src/box/schema.h
@@ -134,14 +134,9 @@ space_cache_find_xc(uint32_t id)
 /**
  * Update contents of the space cache.  Typically the new space is
  * an altered version of the original space.
- * Returns the old space, if any.
  */
-struct space *
-space_cache_replace(struct space *space);
-
-/** Delete a space from the space cache. */
-struct space *
-space_cache_delete(uint32_t id);
+void
+space_cache_replace(struct space *old_space, struct space *new_space);
 
 void
 schema_init();
-- 
2.11.0