SERVER-53274 Avoid bumping all chunk versions after writing 'history' field on FCV upgrade to 4.0.

Instead, bump only one chunk per shard to satisfy the reqirements
imposed by SERVER-33356

1 files changed, 10 insertions, 18 deletions

diff --git a/src/mongo/db/s/config/sharding_catalog_manager_chunk_operations.cpp b/src/mongo/db/s/config/sharding_catalog_manager_chunk_operations.cpp
index 033a96c6a25..564b3dcf4e7 100644
--- a/src/mongo/db/s/config/sharding_catalog_manager_chunk_operations.cpp
+++ b/src/mongo/db/s/config/sharding_catalog_manager_chunk_operations.cpp
@@ -51,6 +51,7 @@
 #include "mongo/s/client/shard_registry.h"
 #include "mongo/s/grid.h"
 #include "mongo/s/shard_key_pattern.h"
+#include "mongo/stdx/unordered_set.h"
 #include "mongo/util/fail_point_service.h"
 #include "mongo/util/log.h"
 #include "mongo/util/mongoutils/str.h"
@@ -940,6 +941,7 @@ Status ShardingCatalogManager::upgradeChunksHistory(OperationContext* opCtx,
                                              0,
                                              currentCollectionVersion.getValue().epoch());
 
+    stdx::unordered_set<ShardId, ShardId::Hasher> bumpedShards;
     for (const auto& chunk : chunksVector) {
         auto swChunk = ChunkType::fromConfigBSON(chunk);
         if (!swChunk.isOK()) {
@@ -948,10 +950,14 @@ Status ShardingCatalogManager::upgradeChunksHistory(OperationContext* opCtx,
         auto& upgradeChunk = swChunk.getValue();
 
         if (upgradeChunk.getHistory().empty()) {
-
-            // Bump the version.
-            upgradeChunk.setVersion(newCollectionVersion);
-            newCollectionVersion.incMajor();
+            // Bump the version for only one chunk per shard to satisfy the requirement imposed by
+            // SERVER-33356
+            const auto& shardId = upgradeChunk.getShard();
+            if (!bumpedShards.count(shardId)) {
+                upgradeChunk.setVersion(newCollectionVersion);
+                newCollectionVersion.incMajor();
+                bumpedShards.emplace(shardId);
+            }
 
             // Construct the fresh history.
             upgradeChunk.setHistory({ChunkHistory{validAfter, upgradeChunk.getShard()}});
@@ -1004,16 +1010,6 @@ Status ShardingCatalogManager::downgradeChunksHistory(OperationContext* opCtx,
                               << ", but found no chunks"};
     }
 
-    const auto currentCollectionVersion = _findCollectionVersion(opCtx, nss, collectionEpoch);
-    if (!currentCollectionVersion.isOK()) {
-        return currentCollectionVersion.getStatus();
-    }
-
-    // Bump the version.
-    auto newCollectionVersion = ChunkVersion(currentCollectionVersion.getValue().majorVersion() + 1,
-                                             0,
-                                             currentCollectionVersion.getValue().epoch());
-
     for (const auto& chunk : chunksVector) {
         auto swChunk = ChunkType::fromConfigBSON(chunk);
         if (!swChunk.isOK()) {
@@ -1021,10 +1017,6 @@ Status ShardingCatalogManager::downgradeChunksHistory(OperationContext* opCtx,
         }
         auto& downgradeChunk = swChunk.getValue();
 
-        // Bump the version.
-        downgradeChunk.setVersion(newCollectionVersion);
-        newCollectionVersion.incMajor();
-
         // Clear the history.
         downgradeChunk.setHistory({});