SERVER-69429 Check shard key compatibility during collMod convert to unique

(cherry picked from commit 12165e687bc06fbf5df03bfef5d570e9dae7b0e9)

2 files changed, 36 insertions, 1 deletions

diff --git a/jstests/noPassthrough/sharding_index_uniqueness.js b/jstests/noPassthrough/sharding_index_uniqueness.js
index 23cfcbd9a98..b719c656581 100644
--- a/jstests/noPassthrough/sharding_index_uniqueness.js
+++ b/jstests/noPassthrough/sharding_index_uniqueness.js
@@ -5,6 +5,8 @@
  *
  * @tags: [
  *   requires_sharding,
+ *   # TODO(SERVER-61182): Fix WiredTigerKVEngine::alterIdentMetadata() under inMemory.
+ *   requires_persistence,
  * ]
  */
 
@@ -45,5 +47,19 @@ assert.commandFailedWithCode(coll.createIndex({a: 1}, {unique: 1}), ErrorCodes.C
 assert.commandWorked(coll.createIndex({b: 1, a: 1}, {prepareUnique: 1}));
 assert.commandWorked(coll.createIndex({b: 1, c: 1}, {unique: 1}));
 
+// Cannot convert an index to prepareUnique with a conflicting shard key.
+coll = db[collNamePrefix + count++];
+assert.commandWorked(st.s.adminCommand({shardCollection: coll.getFullName(), key: {b: 1}}));
+assert.commandWorked(coll.createIndex({a: 1}));
+assert.commandFailedWithCode(
+    db.runCommand({collMod: coll.getName(), index: {keyPattern: {a: 1}, prepareUnique: true}}),
+    ErrorCodes.InvalidOptions);
+// Can convert an index to prepareUnique and unique with a compatible shard key.
+assert.commandWorked(coll.createIndex({b: 1, d: 1}));
+assert.commandWorked(db.runCommand(
+    {collMod: coll.getName(), index: {keyPattern: {b: 1, d: 1}, prepareUnique: true}}));
+assert.commandWorked(
+    db.runCommand({collMod: coll.getName(), index: {keyPattern: {b: 1, d: 1}, unique: true}}));
+
 st.stop();
 })();
diff --git a/src/mongo/db/catalog/coll_mod.cpp b/src/mongo/db/catalog/coll_mod.cpp
index 9fc32c239cd..cedf7a39cef 100644
--- a/src/mongo/db/catalog/coll_mod.cpp
+++ b/src/mongo/db/catalog/coll_mod.cpp
@@ -62,6 +62,7 @@
 #include "mongo/db/views/view_catalog_helpers.h"
 #include "mongo/idl/command_generic_argument.h"
 #include "mongo/logv2/log.h"
+#include "mongo/s/grid.h"
 #include "mongo/util/fail_point.h"
 #include "mongo/util/version/releases.h"
 #include "mongo/util/visit_helper.h"
@@ -338,7 +339,7 @@ StatusWith<std::pair<ParsedCollModRequest, BSONObj>> parseCollModRequest(Operati
             if (cmrIndex->idx->unique()) {
                 indexForOplog->setUnique(boost::none);
             } else {
-                // Disallow one-step unique convertion. The user has to set
+                // Disallow one-step unique conversion. The user has to set
                 // 'prepareUnique' to true first.
                 if (!cmrIndex->idx->prepareUnique()) {
                     return Status(ErrorCodes::InvalidOptions,
@@ -379,6 +380,24 @@ StatusWith<std::pair<ParsedCollModRequest, BSONObj>> parseCollModRequest(Operati
                 cmrIndex->idx->unique()) {
                 indexForOplog->setPrepareUnique(boost::none);
             } else {
+                // Checks if the index key pattern conflicts with the shard key pattern.
+                if (auto catalogClient = Grid::get(opCtx)->catalogClient()) {
+                    try {
+                        auto shardedColl = catalogClient->getCollection(opCtx, nss);
+                        const ShardKeyPattern shardKeyPattern(shardedColl.getKeyPattern());
+                        if (!shardKeyPattern.isIndexUniquenessCompatible(
+                                cmrIndex->idx->keyPattern())) {
+                            return {ErrorCodes::InvalidOptions,
+                                    fmt::format(
+                                        "cannot set 'prepareUnique' for index {} with shard key "
+                                        "pattern {}",
+                                        cmrIndex->idx->keyPattern().toString(),
+                                        shardKeyPattern.toBSON().toString())};
+                        }
+                    } catch (ExceptionFor<ErrorCodes::NamespaceNotFound>&) {
+                        // The collection is unsharded or doesn't exist.
+                    }
+                }
                 cmrIndex->indexPrepareUnique = cmdIndex.getPrepareUnique();
             }
         }