Bubble collapse.

Signal/src/ViewControllers/DebugUI/DebugUIMessages.m

@@ -43,6 +43,11 @@ NS_ASSUME_NONNULL_BEGIN
 
     NSMutableArray<OWSTableItem *> *items = [NSMutableArray new];
 
+    [items addObject:[OWSTableItem itemWithTitle:@"Delete all messages in thread"
+                                     actionBlock:^{
+                                         [DebugUIMessages deleteAllMessagesInThread:thread];
+                                     }]];
+
     for (DebugUIMessagesAction *action in @[
              [DebugUIMessages sendMessageVariationsAction:thread],
              // Send Media
@@ -2589,6 +2594,14 @@ NS_ASSUME_NONNULL_BEGIN
     };
 }
 
++ (void)deleteAllMessagesInThread:(TSThread *)thread
+{
+    [OWSPrimaryStorage.sharedManager.newDatabaseConnection
+        readWriteWithBlock:^(YapDatabaseReadWriteTransaction *transaction) {
+            [thread removeAllThreadInteractionsWithTransaction:transaction];
+        }];
+}
+
 @end
 
 NS_ASSUME_NONNULL_END

SignalServiceKit/src/Contacts/TSThread.h

@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
 //
 
 #import "TSYapDatabaseObject.h"
@@ -133,6 +133,8 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (void)unarchiveThreadWithTransaction:(YapDatabaseReadWriteTransaction *)transaction;
 
+- (void)removeAllThreadInteractionsWithTransaction:(YapDatabaseReadWriteTransaction *)transaction;
+
 #pragma mark Drafts
 
 /**

SignalServiceKit/src/Contacts/TSThread.m

@@ -49,8 +49,13 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (void)removeWithTransaction:(YapDatabaseReadWriteTransaction *)transaction
 {
-    [super removeWithTransaction:transaction];
+    [self removeAllThreadInteractionsWithTransaction:transaction];
 
+    [super removeWithTransaction:transaction];
+}
+
+- (void)removeAllThreadInteractionsWithTransaction:(YapDatabaseReadWriteTransaction *)transaction
+{
     // We can't safely delete interactions while enumerating them, so
     // we collect and delete separately.
     //