MB-41321: 4/4 Remove KVStore/Flush notification of dropped collection

Now that flush.cc has visibility of the all dropped collections there
is no need for each KVStore to signal to Flush that a collection drop
was committed.

Change-Id: If4973680145da9b00bd6babec44badd98b32892e
Reviewed-on: http://review.couchbase.org/c/kv_engine/+/137498
Tested-by: Build Bot <[email protected]>
Reviewed-by: Dave Rigby <[email protected]>

Author: jimwwalker

engines/ep/src/collections/flush.cc

@@ -150,7 +150,7 @@ void Flush::notifyManifestOfAnyDroppedCollections() {
 }
 
 void Flush::checkAndTriggerPurge(Vbid vbid, KVBucket& bucket) const {
-    if (needsPurge) {
+    if (!droppedCollections.empty()) {
         triggerPurge(vbid, bucket);
     }
 }

engines/ep/src/collections/flush.h

@@ -121,10 +121,6 @@ class Flush {
      */
     static void triggerPurge(Vbid vbid, KVBucket& bucket);
 
-    void setNeedsPurge() {
-        needsPurge = true;
-    }
-
     /**
      * Set that the KVStore needs to commit the data held in this object.
      */
@@ -402,12 +398,6 @@ class Flush {
      */
     Manifest& manifest;
 
-    /**
-     * Set to true when any collection was dropped by the flusher and purging is
-     * required to remove all items of the dropped collection(s)
-     */
-    bool needsPurge = false;
-
     /**
      * Set to true when any of the fields in this structure have data which
      * should be saved in the KVStore update/commit. The underlying KVStore

engines/ep/src/couch-kvstore/couch-kvstore.cc

@@ -3623,7 +3623,6 @@ void CouchKVStore::updateCollectionsMeta(
 
     if (collectionsFlush.isDroppedCollectionsChanged()) {
         updateDroppedCollections(db, collectionsFlush);
-        collectionsFlush.setNeedsPurge();
     }
 
     if (collectionsFlush.isScopesChanged()) {

engines/ep/src/magma-kvstore/magma-kvstore.cc

@@ -2158,18 +2158,12 @@ void MagmaKVStore::updateCollectionsMeta(
         Collections::VB::Flush& collectionsFlush) {
     updateManifestUid(localDbReqs, collectionsFlush);
 
-    // If the updateOpenCollections reads the dropped collections, it can pass
-    // them via this optional to updateDroppedCollections, thus we only read
-    // the dropped list once per update.
-    std::optional<std::vector<Collections::KVStore::DroppedCollection>> dropped;
-
     if (collectionsFlush.isOpenCollectionsChanged()) {
         updateOpenCollections(vbid, localDbReqs, collectionsFlush);
     }
 
     if (collectionsFlush.isDroppedCollectionsChanged()) {
         updateDroppedCollections(vbid, localDbReqs, collectionsFlush);
-        collectionsFlush.setNeedsPurge();
     }
 
     if (collectionsFlush.isScopesChanged()) {