Lists AOF rewrite using variadic RPUSH (work in progress)

src/aof.c

@@ -422,8 +422,62 @@ int rioWriteBulkObject(rio *r, robj *obj) {
     }
 }
 
+/* Emit the commands needed to rebuild a list object.
+ * The function returns 0 on error, 1 on success. */
+int rewriteListObject(rio *r, robj *key, robj *o) {
+    long long count = 0, items = listTypeLength(o);
+
+    if (o->encoding == REDIS_ENCODING_ZIPLIST) {
+        unsigned char *zl = o->ptr;
+        unsigned char *p = ziplistIndex(zl,0);
+        unsigned char *vstr;
+        unsigned int vlen;
+        long long vlong;
+
+        while(ziplistGet(p,&vstr,&vlen,&vlong)) {
+            if (count == 0) {
+                int cmd_items = (items > REDIS_AOFREWRITE_ITEMS_PER_CMD) ?
+                    REDIS_AOFREWRITE_ITEMS_PER_CMD : items;
+                if (rioWriteBulkCount(r,'*',2+cmd_items) == 0) return 0;
+                if (rioWriteBulkString(r,"RPUSH",5) == 0) return 0;
+                if (rioWriteBulkObject(r,key) == 0) return 0;
+            }
+            if (vstr) {
+                if (rioWriteBulkString(r,(char*)vstr,vlen) == 0) return 0;
+            } else {
+                if (rioWriteBulkLongLong(r,vlong) == 0) return 0;
+            }
+            p = ziplistNext(zl,p);
+            if (++count == REDIS_AOFREWRITE_ITEMS_PER_CMD) count = 0;
+            items--;
+        }
+    } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
+        list *list = o->ptr;
+        listNode *ln;
+        listIter li;
+
+        listRewind(list,&li);
+        while((ln = listNext(&li))) {
+            robj *eleobj = listNodeValue(ln);
+
+            if (rioWriteBulkCount(r,'*',3) == 0) return 0;
+            if (rioWriteBulkString(r,"RPUSH",5) == 0) return 0;
+            if (rioWriteBulkObject(r,key) == 0) return 0;
+            if (rioWriteBulkObject(r,eleobj) == 0) return 0;
+        }
+    } else {
+        redisPanic("Unknown list encoding");
+    }
+    return 1;
+}
+
 /* Write a sequence of commands able to fully rebuild the dataset into
- * "filename". Used both by REWRITEAOF and BGREWRITEAOF. */
+ * "filename". Used both by REWRITEAOF and BGREWRITEAOF.
+ *
+ * In order to minimize the number of commands needed in the rewritten
+ * log Redis uses variadic commands when possible, such as RPUSH, SADD
+ * and ZADD. However at max REDIS_AOFREWRITE_ITEMS_PER_CMD items per time
+ * are inserted using a single command. */
 int rewriteAppendOnlyFile(char *filename) {
     dictIterator *di = NULL;
     dictEntry *de;
@@ -479,43 +533,7 @@ int rewriteAppendOnlyFile(char *filename) {
                 if (rioWriteBulkObject(&aof,&key) == 0) goto werr;
                 if (rioWriteBulkObject(&aof,o) == 0) goto werr;
             } else if (o->type == REDIS_LIST) {
-                /* Emit the RPUSHes needed to rebuild the list */
-                char cmd[]="*3\r\n$5\r\nRPUSH\r\n";
-                if (o->encoding == REDIS_ENCODING_ZIPLIST) {
-                    unsigned char *zl = o->ptr;
-                    unsigned char *p = ziplistIndex(zl,0);
-                    unsigned char *vstr;
-                    unsigned int vlen;
-                    long long vlong;
-
-                    while(ziplistGet(p,&vstr,&vlen,&vlong)) {
-                        if (rioWrite(&aof,cmd,sizeof(cmd)-1) == 0) goto werr;
-                        if (rioWriteBulkObject(&aof,&key) == 0) goto werr;
-                        if (vstr) {
-                            if (rioWriteBulkString(&aof,(char*)vstr,vlen) == 0)
-                                goto werr;
-                        } else {
-                            if (rioWriteBulkLongLong(&aof,vlong) == 0)
-                                goto werr;
-                        }
-                        p = ziplistNext(zl,p);
-                    }
-                } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
-                    list *list = o->ptr;
-                    listNode *ln;
-                    listIter li;
-
-                    listRewind(list,&li);
-                    while((ln = listNext(&li))) {
-                        robj *eleobj = listNodeValue(ln);
-
-                        if (rioWrite(&aof,cmd,sizeof(cmd)-1) == 0) goto werr;
-                        if (rioWriteBulkObject(&aof,&key) == 0) goto werr;
-                        if (rioWriteBulkObject(&aof,eleobj) == 0) goto werr;
-                    }
-                } else {
-                    redisPanic("Unknown list encoding");
-                }
+                if (rewriteListObject(&aof,&key,o) == 0) goto werr;
             } else if (o->type == REDIS_SET) {
                 char cmd[]="*3\r\n$4\r\nSADD\r\n";
 

src/redis.h

@@ -54,6 +54,7 @@
 #define REDIS_MAX_LOGMSG_LEN    1024 /* Default maximum length of syslog messages */
 #define REDIS_AUTO_AOFREWRITE_PERC  100
 #define REDIS_AUTO_AOFREWRITE_MIN_SIZE (1024*1024)
+#define REDIS_AOFREWRITE_ITEMS_PER_CMD 64
 #define REDIS_SLOWLOG_LOG_SLOWER_THAN 10000
 #define REDIS_SLOWLOG_MAX_LEN 64
 #define REDIS_MAX_CLIENTS 10000