[PATCH 2/3] vinyl: don't populate cache if box.cfg.vinyl_cache is 0

[Vladimir Davydov]

Currently, new entries are added to the cache even if the limit is set
to 0, which is obviously incorrect. Fix it. This might be useful for
debugging and/or performance evaluation.

Closes #3172
---
 src/box/vy_cache.c        |  5 +++++
 test/vinyl/cache.result   | 22 ++++++++++++++++++++++
 test/vinyl/cache.test.lua |  7 +++++++
 3 files changed, 34 insertions(+)

diff --git a/src/box/vy_cache.c b/src/box/vy_cache.c
index 8a6c53f7..121a4263 100644
--- a/src/box/vy_cache.c
+++ b/src/box/vy_cache.c
@@ -217,6 +217,11 @@ vy_cache_add(struct vy_cache *cache, struct tuple *stmt,
 	     struct tuple *prev_stmt, const struct tuple *key,
 	     enum iterator_type order)
 {
+	if (cache->env->mem_quota == 0) {
+		/* Cache is disabled. */
+		return;
+	}
+
 	/* Delete some entries if quota overused */
 	vy_cache_gc(cache->env);
 
diff --git a/test/vinyl/cache.result b/test/vinyl/cache.result
index 3ed4d0f9..b4812297 100644
--- a/test/vinyl/cache.result
+++ b/test/vinyl/cache.result
@@ -1051,6 +1051,28 @@ box.info.vinyl().cache.used
 ---
 - 0
 ...
+-- Make sure cache is not populated if box.cfg.vinyl_cache is set to 0
+st1 = s.index.pk:info().cache
+---
+...
+#s:select()
+---
+- 100
+...
+for i = 1, 100 do s:get{i} end
+---
+...
+st2 = s.index.pk:info().cache
+---
+...
+st2.put.rows - st1.put.rows
+---
+- 0
+...
+box.info.vinyl().cache.used
+---
+- 0
+...
 s:drop()
 ---
 ...
diff --git a/test/vinyl/cache.test.lua b/test/vinyl/cache.test.lua
index 40d55abf..9ff77cbb 100644
--- a/test/vinyl/cache.test.lua
+++ b/test/vinyl/cache.test.lua
@@ -373,5 +373,12 @@ box.cfg{vinyl_cache = 50 * 1000}
 box.info.vinyl().cache.used
 box.cfg{vinyl_cache = 0}
 box.info.vinyl().cache.used
+-- Make sure cache is not populated if box.cfg.vinyl_cache is set to 0
+st1 = s.index.pk:info().cache
+#s:select()
+for i = 1, 100 do s:get{i} end
+st2 = s.index.pk:info().cache
+st2.put.rows - st1.put.rows
+box.info.vinyl().cache.used
 s:drop()
 box.cfg{vinyl_cache = vinyl_cache}
-- 
2.11.0