From 362e187011bd8df54f3257ad014812728024fe1e Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Tue, 25 Jun 2019 13:08:56 +0300
Subject: [PATCH] lib/storage: use unversioned keys for tag cache in extDB

Data in ExtDB cannot be changed, so it is OK to use unversioned keys for tag cache.
This should improve performance for index lookups over big amount of time series.
---
 lib/storage/index_db.go | 41 ++++++++++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/lib/storage/index_db.go b/lib/storage/index_db.go
index b0689c497..3517346c5 100644
--- a/lib/storage/index_db.go
+++ b/lib/storage/index_db.go
@@ -340,22 +340,25 @@ func (db *indexDB) putMetricNameToCache(metricID uint64, metricName []byte) {
 	db.metricNameCache.Set(key[:], metricName)
 }
 
-func (db *indexDB) marshalTagFiltersKeyVersioned(dst []byte, tfss []*TagFilters) []byte {
+func (db *indexDB) marshalTagFiltersKey(dst []byte, tfss []*TagFilters, versioned bool) []byte {
 	if len(tfss) == 0 {
 		return nil
 	}
-	k := accountProjectKey{
-		AccountID: tfss[0].accountID,
-		ProjectID: tfss[0].projectID,
-	}
-	db.tagCachePrefixesLock.RLock()
-	prefix := db.tagCachePrefixes[k]
-	db.tagCachePrefixesLock.RUnlock()
-	if prefix == 0 {
-		// Create missing prefix.
-		// It is OK if multiple concurrent goroutines call invalidateTagCache
-		// for the same (accountID, projectID).
-		prefix = db.invalidateTagCache(k.AccountID, k.ProjectID)
+	prefix := ^uint64(0)
+	if versioned {
+		k := accountProjectKey{
+			AccountID: tfss[0].accountID,
+			ProjectID: tfss[0].projectID,
+		}
+		db.tagCachePrefixesLock.RLock()
+		prefix = db.tagCachePrefixes[k]
+		db.tagCachePrefixesLock.RUnlock()
+		if prefix == 0 {
+			// Create missing prefix.
+			// It is OK if multiple concurrent goroutines call invalidateTagCache
+			// for the same (accountID, projectID).
+			prefix = db.invalidateTagCache(k.AccountID, k.ProjectID)
+		}
 	}
 	dst = encoding.MarshalUint64(dst, prefix)
 	for _, tfs := range tfss {
@@ -967,7 +970,7 @@ func (db *indexDB) searchTSIDs(tfss []*TagFilters, tr TimeRange, maxMetrics int)
 	tfKeyBuf := tagFiltersKeyBufPool.Get()
 	defer tagFiltersKeyBufPool.Put(tfKeyBuf)
 
-	tfKeyBuf.B = db.marshalTagFiltersKeyVersioned(tfKeyBuf.B[:0], tfss)
+	tfKeyBuf.B = db.marshalTagFiltersKey(tfKeyBuf.B[:0], tfss, true)
 	tsids, ok := db.getFromTagCache(tfKeyBuf.B)
 	if ok {
 		// Fast path - tsids found in the cache.
@@ -984,7 +987,12 @@ func (db *indexDB) searchTSIDs(tfss []*TagFilters, tr TimeRange, maxMetrics int)
 
 	var extTSIDs []TSID
 	if db.doExtDB(func(extDB *indexDB) {
-		tsids, ok := extDB.getFromTagCache(tfKeyBuf.B)
+		tfKeyExtBuf := tagFiltersKeyBufPool.Get()
+		defer tagFiltersKeyBufPool.Put(tfKeyExtBuf)
+
+		// Data in extDB cannot be changed, so use unversioned keys for tag cache.
+		tfKeyExtBuf.B = extDB.marshalTagFiltersKey(tfKeyExtBuf.B[:0], tfss, false)
+		tsids, ok := extDB.getFromTagCache(tfKeyExtBuf.B)
 		if ok {
 			extTSIDs = tsids
 			return
@@ -993,8 +1001,7 @@ func (db *indexDB) searchTSIDs(tfss []*TagFilters, tr TimeRange, maxMetrics int)
 		extTSIDs, err = is.searchTSIDs(tfss, tr, maxMetrics)
 		extDB.putIndexSearch(is)
 
-		// Do not store found tsids into extDB.tagCache,
-		// since they will be stored into outer cache instead.
+		db.putToTagCache(tsids, tfKeyExtBuf.B)
 	}) {
 		if err != nil {
 			return nil, err