SERVER-23655 invalidate CollectionInfoCache on index build

This forces a rebuild of a collection's info cache once an index build has
started, rather than waiting until the build has completed. This way,
updates occurring while a background index build is in progress correctly know
that the index will be affected and perform the update accordingly.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/mongo/db/catalog/index_catalog.cpp b/src/mongo/db/catalog/index_catalog.cpp
index 8662eb0f906..b572a66426e 100644
--- a/src/mongo/db/catalog/index_catalog.cpp
+++ b/src/mongo/db/catalog/index_catalog.cpp
@@ -365,6 +365,11 @@ Status IndexCatalog::IndexBuildBlock::init() {
     const bool initFromDisk = false;
     _entry = _catalog->_setupInMemoryStructures(_txn, descriptorCleaner.release(), initFromDisk);
 
+    // Register this index with the CollectionInfoCache to regenerate the cache. This way, updates
+    // occurring while an index is being build in the background will be aware of whether or not
+    // they need to modify any indexes.
+    _collection->infoCache()->addedIndex(_txn, descriptor);
+
     return Status::OK();
 }
 
@@ -413,8 +418,6 @@ void IndexCatalog::IndexBuildBlock::success() {
     });
 
     entry->setIsReady(true);
-
-    collection->infoCache()->addedIndex(_txn, desc);
 }
 
 namespace {