diff --git a/src/db.c b/src/db.c
index c7940d73..268e7c38 100644
--- a/src/db.c
+++ b/src/db.c
@@ -471,7 +471,7 @@ void selectCommand(client *c) {
         return;
     }
     if (selectDb(c,id) == C_ERR) {
-        addReplyError(c,"invalid DB index");
+        addReplyError(c,"DB index is out of range");
     } else {
         addReply(c,shared.ok);
     }
@@ -926,6 +926,91 @@ void moveCommand(client *c) {
     addReply(c,shared.cone);
 }
 
+/* Helper function for dbSwapDatabases(): scans the list of keys that have
+ * one or more blocked clients for B[LR]POP or other list blocking commands
+ * and signal the keys are ready if they are lists. See the comment where
+ * the function is used for more info. */
+void scanDatabaseForReadyLists(redisDb *db) {
+    dictEntry *de;
+    dictIterator *di = dictGetSafeIterator(db->blocking_keys);
+    while((de = dictNext(di)) != NULL) {
+        robj *key = dictGetKey(de);
+        robj *value = lookupKey(db,key,LOOKUP_NOTOUCH);
+        if (value && value->type == OBJ_LIST)
+            signalListAsReady(db, key);
+    }
+    dictReleaseIterator(di);
+}
+
+/* Swap two databases at runtime so that all clients will magically see
+ * the new database even if already connected. Note that the client
+ * structure c->db points to a given DB, so we need to be smarter and
+ * swap the underlying referenced structures, otherwise we would need
+ * to fix all the references to the Redis DB structure.
+ *
+ * Returns C_ERR if at least one of the DB ids are out of range, otherwise
+ * C_OK is returned. */
+int dbSwapDatabases(int id1, int id2) {
+    if (id1 < 0 || id1 >= server.dbnum ||
+        id2 < 0 || id2 >= server.dbnum) return C_ERR;
+    if (id1 == id2) return C_OK;
+    redisDb aux = server.db[id1];
+    redisDb *db1 = &server.db[id1], *db2 = &server.db[id2];
+
+    /* Swap hash tables. Note that we don't swap blocking_keys,
+     * ready_keys and watched_keys, since we want clients to
+     * remain in the same DB they were. */
+    db1->dict = db2->dict;
+    db1->expires = db2->expires;
+    db1->avg_ttl = db2->avg_ttl;
+
+    db2->dict = aux.dict;
+    db2->expires = aux.expires;
+    db2->avg_ttl = aux.avg_ttl;
+
+    /* Now we need to handle clients blocked on lists: as an effect
+     * of swapping the two DBs, a client that was waiting for list
+     * X in a given DB, may now actually be unblocked if X happens
+     * to exist in the new version of the DB, after the swap.
+     *
+     * However normally we only do this check for efficiency reasons
+     * in dbAdd() when a list is created. So here we need to rescan
+     * the list of clients blocked on lists and signal lists as ready
+     * if needed. */
+    scanDatabaseForReadyLists(db1);
+    scanDatabaseForReadyLists(db2);
+    return C_OK;
+}
+
+/* SWAPDB db1 db2 */
+void swapdbCommand(client *c) {
+    long id1, id2;
+
+    /* Not allowed in cluster mode: we have just DB 0 there. */
+    if (server.cluster_enabled) {
+        addReplyError(c,"SWAPDB is not allowed in cluster mode");
+        return;
+    }
+
+    /* Get the two DBs indexes. */
+    if (getLongFromObjectOrReply(c, c->argv[1], &id1,
+        "invalid first DB index") != C_OK)
+        return;
+
+    if (getLongFromObjectOrReply(c, c->argv[2], &id2,
+        "invalid second DB index") != C_OK)
+        return;
+
+    /* Swap... */
+    if (dbSwapDatabases(id1,id2) == C_ERR) {
+        addReplyError(c,"DB index is out of range");
+        return;
+    } else {
+        server.dirty++;
+        addReply(c,shared.ok);
+    }
+}
+
 /*-----------------------------------------------------------------------------
  * Expires API
  *----------------------------------------------------------------------------*/
diff --git a/src/server.c b/src/server.c
index a0549185..7e9b962b 100644
--- a/src/server.c
+++ b/src/server.c
@@ -219,6 +219,7 @@ struct redisCommand redisCommandTable[] = {
     {"msetnx",msetnxCommand,-3,"wm",0,NULL,1,-1,2,0,0},
     {"randomkey",randomkeyCommand,1,"rR",0,NULL,0,0,0,0,0},
     {"select",selectCommand,2,"lF",0,NULL,0,0,0,0,0},
+    {"swapdb",swapdbCommand,3,"wF",0,NULL,0,0,0,0,0},
     {"move",moveCommand,3,"wF",0,NULL,1,1,1,0,0},
     {"rename",renameCommand,3,"w",0,NULL,1,2,1,0,0},
     {"renamenx",renamenxCommand,3,"wF",0,NULL,1,2,1,0,0},
diff --git a/src/server.h b/src/server.h
index 69ee52e6..b5dbaf0a 100644
--- a/src/server.h
+++ b/src/server.h
@@ -1731,6 +1731,7 @@ void incrbyCommand(client *c);
 void decrbyCommand(client *c);
 void incrbyfloatCommand(client *c);
 void selectCommand(client *c);
+void swapdbCommand(client *c);
 void randomkeyCommand(client *c);
 void keysCommand(client *c);
 void scanCommand(client *c);