Reset average ttl when empty databases (#8106)

On FLUSHDB or full sync, reset old average TTL stat.
This Stat is incrementally collected by the master over time when it searches for expired keys. 

(cherry picked from commit c85bf2352d2a3dd04872124d33066403b114a7e7)

1 files changed, 3 insertions, 0 deletions

diff --git a/src/db.c b/src/db.c
index c896c10fd..09ba38348 100644
--- a/src/db.c
+++ b/src/db.c
@@ -416,6 +416,9 @@ long long emptyDbGeneric(redisDb *dbarray, int dbnum, int flags, void(callback)(
             dictEmpty(dbarray[j].dict,callback);
             dictEmpty(dbarray[j].expires,callback);
         }
+        /* Because we will start a new database, reset average ttl. */
+        dbarray[j].avg_ttl = 0;
+        dbarray[j].expires_cursor = 0;
     }
 
     /* Post-flush actions */