From 99c807bd43a092627d2811306d56c474c88c9701 Mon Sep 17 00:00:00 2001
From: Josh Hershberg <yehoshua@redis.com>
Date: Wed, 26 Mar 2025 14:28:49 +0200
Subject: [PATCH] RDB: Filter keys in unowned slots

This PR excludes unowned slots while writing an RDB.
This PR is a preperation for future work to do with
resharding. In addition, a "debug set key value"
command is added to fascilitate testing of this
feature.

Signed-off-by: Josh Hershberg <yehoshua@redis.com>
---
 src/debug.c   |  5 +++++
 src/kvstore.c |  5 +++++
 src/kvstore.h |  1 +
 src/rdb.c     | 14 ++++++++++++++
 4 files changed, 25 insertions(+)

diff --git a/src/debug.c b/src/debug.c
index 5584ae387..f7c61256b 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -496,6 +496,8 @@ void debugCommand(client *c) {
 "    Output SHA and content of all scripts or of a specific script with its SHA.",
 "MARK-INTERNAL-CLIENT [UNMARK]",
 "    Promote the current connection to an internal connection.",
+"SET key value",
+"    Set a key, even if it is in a slot not owned by this node.",
 NULL
         };
         addExtendedReplyHelp(c, help, clusterDebugCommandExtendedHelp());
@@ -1087,6 +1089,9 @@ NULL
             addReplySubcommandSyntaxError(c);
             return;
         }
+    } else if (!strcasecmp(c->argv[1]->ptr, "set") && c->argc == 4) {
+        setKey(c,c->db, c->argv[2], c->argv[3], SETKEY_ADD_OR_UPDATE);
+        addReply(c, shared.ok);
     } else if(!handleDebugClusterCommand(c)) {
         addReplySubcommandSyntaxError(c);
         return;
diff --git a/src/kvstore.c b/src/kvstore.c
index d7948c9ab..ac87c7903 100644
--- a/src/kvstore.c
+++ b/src/kvstore.c
@@ -654,6 +654,11 @@ dictEntry *kvstoreIteratorNext(kvstoreIterator *kvs_it) {
     return de;
 }
 
+void kvstoreSkipToNextDict(kvstoreIterator *kvs_it) {
+    dict *d = kvstoreIteratorNextDict(kvs_it);
+    if (d) dictInitSafeIterator(&kvs_it->di, d);
+}
+
 /* This method traverses through kvstore dictionaries and triggers a resize.
  * It first tries to shrink if needed, and if it isn't, it tries to expand. */
 void kvstoreTryResizeDicts(kvstore *kvs, int limit) {
diff --git a/src/kvstore.h b/src/kvstore.h
index c077dd625..ee57e5232 100644
--- a/src/kvstore.h
+++ b/src/kvstore.h
@@ -68,6 +68,7 @@ uint64_t kvstoreGetHash(kvstore *kvs, const void *key);
 kvstoreIterator *kvstoreIteratorInit(kvstore *kvs);
 void kvstoreIteratorRelease(kvstoreIterator *kvs_it);
 dict *kvstoreIteratorNextDict(kvstoreIterator *kvs_it);
+void kvstoreSkipToNextDict(kvstoreIterator *kvs_it);
 int kvstoreIteratorGetCurrentDictIndex(kvstoreIterator *kvs_it);
 dictEntry *kvstoreIteratorNext(kvstoreIterator *kvs_it);
 
diff --git a/src/rdb.c b/src/rdb.c
index 7a072cad5..e1e0e1251 100644
--- a/src/rdb.c
+++ b/src/rdb.c
@@ -20,6 +20,7 @@
 #include "functions.h"
 #include "intset.h"  /* Compact integer set structure */
 #include "bio.h"
+#include "cluster.h"
 
 #include <math.h>
 #include <fcntl.h>
@@ -1396,9 +1397,22 @@ ssize_t rdbSaveDb(rio *rdb, int dbid, int rdbflags, long *key_counter) {
 
     kvs_it = kvstoreIteratorInit(db->keys);
     int last_slot = -1;
+    clusterNode *myNode = NULL;
+    if (server.cluster_enabled) {
+        myNode = getMyClusterNode();
+        if (NULL == myNode) {
+            goto werr;
+        }
+    }
     /* Iterate this DB writing every entry */
     while ((de = kvstoreIteratorNext(kvs_it)) != NULL) {
         int curr_slot = kvstoreIteratorGetCurrentDictIndex(kvs_it);
+        if (server.cluster_enabled) {
+            if (getNodeBySlot(curr_slot) != myNode) {
+                kvstoreSkipToNextDict(kvs_it);
+                continue;
+            }
+        }
         /* Save slot info. */
         if (server.cluster_enabled && curr_slot != last_slot) {
             if ((res = rdbSaveType(rdb, RDB_OPCODE_SLOT_INFO)) < 0) goto werr;