SERVER-100072 Assert shard key is the same when forceRedistribution passed to reshardCollection (#34686)

GitOrigin-RevId: c3efe38c902eb66274623f1ffaf4babb513e7292

jstests/core_sharding/resharding/reshard_collection_basic.js

@@ -120,7 +120,7 @@ assert.commandFailedWithCode(db.adminCommand({
 
 assert.commandFailedWithCode(db.adminCommand({
     reshardCollection: ns,
-    key: {newKey: 1},
+    key: {oldKey: 1},
     forceRedistribution: true,
     zones: [
         {zone: newZoneName, min: {newKey: 'MinKey'}, max: {newKey: '0'}},
@@ -139,6 +139,23 @@ if (!TestData.implicitlyTrackUnshardedCollectionOnCreation) {
         [ErrorCodes.NamespaceNotFound, ErrorCodes.NamespaceNotSharded]);
 }
 
+// TODO SERVER-103461 Remove version check when 9.0 becomes last LTS.
+const binVersion = assert
+                       .commandWorked(db.adminCommand({
+                           serverStatus: 1,
+                       }))
+                       .version;
+if (MongoRunner.compareBinVersions(binVersion, "8.2") >= 0) {
+    jsTest.log(
+        "Fail if using forceRedistribution and provide a different key than the existing shard key.");
+    assert.commandFailedWithCode(db.adminCommand({
+        reshardCollection: ns,
+        key: {newKey: 1},
+        forceRedistribution: true,
+    }),
+                                 ErrorCodes.InvalidOptions);
+}
+
 /**
  * Success cases
  */

jstests/core_sharding/resharding/reshard_collection_resharding_improvements_basic.js

@@ -118,9 +118,9 @@ const testShardDistribution = (mongos) => {
         "reshardCollection cmd should fail when the shardId in shardDistribution is a shard url.");
     assert.commandFailedWithCode(mongos.adminCommand({
         reshardCollection: ns,
-        key: {newKey: 1},
+        key: {oldKey: 1},
-        forceRedistribution: true,
+        forceRedistribution: false,
-        shardDistribution: [{shard: shardHosts[0], min: {newKey: MinKey}, max: {newKey: MaxKey}}]
+        shardDistribution: [{shard: shardHosts[0], min: {oldKey: MinKey}, max: {oldKey: MaxKey}}]
     }),
                                  ErrorCodes.ShardNotFound);
 

src/mongo/db/s/reshard_collection_coordinator.cpp

@@ -218,6 +218,16 @@ ExecutorFuture<void> ReshardCollectionCoordinator::_runImpl(
                 uassert(ErrorCodes::NamespaceNotSharded,
                         "Collection has to be a sharded collection.",
                         cmOld.isSharded());
+
+                if (_doc.getForceRedistribution() && *_doc.getForceRedistribution()) {
+                    uassert(ErrorCodes::InvalidOptions,
+                            str::stream()
+                                << "The new shard key must be the same as the original shard key "
+                                   "when using the forceRedistribution option. The "
+                                   "forceRedistribution option is meant for redistributing the "
+                                   "collection to a different set of shards.",
+                            cmOld.getShardKeyPattern().isShardKey(_doc.getKey()));
+                }
             }
 
             configsvrReshardCollection.setProvenance(provenance);