From 31222292284aa518f1a1961b3b7df8e47134bac9 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Thu, 30 Dec 2010 19:16:59 +0100
Subject: [PATCH 1/1] handled DEL command as a special optimized case for disk
 store

---
 src/db.c        | 12 ++++++++++++
 src/diskstore.c |  4 ++++
 src/dscache.c   | 22 +++++++++++++++++-----
 src/redis.h     |  1 +
 4 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/src/db.c b/src/db.c
index f3606077..d545345c 100644
--- a/src/db.c
+++ b/src/db.c
@@ -205,10 +205,22 @@ void delCommand(redisClient *c) {
     int deleted = 0, j;
 
     for (j = 1; j < c->argc; j++) {
+        if (server.ds_enabled) {
+            lookupKeyRead(c->db,c->argv[j]);
+            /* FIXME: this can be optimized a lot, no real need to load
+             * a possibly huge value. */
+        }
         if (dbDelete(c->db,c->argv[j])) {
             signalModifiedKey(c->db,c->argv[j]);
             server.dirty++;
             deleted++;
+        } else if (server.ds_enabled) {
+            if (cacheKeyMayExist(c->db,c->argv[j]) &&
+                dsExists(c->db,c->argv[j]))
+            {
+                cacheScheduleForFlush(c->db,c->argv[j]);
+                deleted = 1;
+            }
         }
     }
     addReplyLongLong(c,deleted);
diff --git a/src/diskstore.c b/src/diskstore.c
index 35c591d7..6e59bc67 100644
--- a/src/diskstore.c
+++ b/src/diskstore.c
@@ -262,6 +262,10 @@ int dsDel(redisDb *db, robj *key) {
 }
 
 int dsExists(redisDb *db, robj *key) {
+    char buf[1024];
+
+    dsKeyToPath(db,buf,key);
+    return access(buf,R_OK) == 0;
 }
 
 int dsFlushDb(int dbid) {
diff --git a/src/dscache.c b/src/dscache.c
index 05112cbb..9fc0f5e5 100644
--- a/src/dscache.c
+++ b/src/dscache.c
@@ -304,8 +304,10 @@ void vmThreadedIOCompletedJob(aeEventLoop *el, int fd, void *privdata,
             handleClientsBlockedOnSwappedKey(j->db,j->key);
             freeIOJob(j);
         } else if (j->type == REDIS_IOJOB_SAVE) {
-            redisAssert(j->val->storage == REDIS_DS_SAVING);
-            j->val->storage = REDIS_DS_MEMORY;
+            if (j->val) {
+                redisAssert(j->val->storage == REDIS_DS_SAVING);
+                j->val->storage = REDIS_DS_MEMORY;
+            }
             freeIOJob(j);
         }
         processed++;
@@ -362,11 +364,12 @@ void *IOThreadEntryPoint(void *arg) {
             j->val = dsGet(j->db,j->key,&expire);
             if (j->val) j->expire = expire;
         } else if (j->type == REDIS_IOJOB_SAVE) {
-            redisAssert(j->val->storage == REDIS_DS_SAVING);
-            if (j->val)
+            if (j->val) {
+                redisAssert(j->val->storage == REDIS_DS_SAVING);
                 dsSet(j->db,j->key,j->val);
-            else
+            } else {
                 dsDel(j->db,j->key);
+            }
         }
 
         /* Done: insert the job into the processed queue */
@@ -540,6 +543,15 @@ void cacheCron(void) {
     }
 }
 
+/* ============ Negative caching for diskstore objects ====================== */
+/* Since accesses to keys that don't exist with disk store cost us a disk
+ * access, we need to cache names of keys that do not exist but are frequently
+ * accessed. */
+int cacheKeyMayExist(redisDb *db, robj *key) {
+    /* FIXME: for now we just always return true. */
+    return 1;
+}
+
 /* ============ Virtual Memory - Blocking clients on missing keys =========== */
 
 /* This function makes the clinet 'c' waiting for the key 'key' to be loaded.
diff --git a/src/redis.h b/src/redis.h
index bb9aee7a..15c192cf 100644
--- a/src/redis.h
+++ b/src/redis.h
@@ -808,6 +808,7 @@ void handleClientsBlockedOnSwappedKey(redisDb *db, robj *key);
 int cacheFreeOneEntry(void);
 void cacheScheduleForFlush(redisDb *db, robj *key);
 void cacheCron(void);
+int cacheKeyMayExist(redisDb *db, robj *key);
 
 /* Set data type */
 robj *setTypeCreate(robj *value);
-- 
2.45.2