From d8f493426878254f81e4a0058c514b77fe7f28e9 Mon Sep 17 00:00:00 2001
From: Nicola Cabiddu <nicola.cabiddu@mongodb.com>
Date: Wed, 20 Mar 2024 18:56:07 +0000
Subject: [PATCH] initial support collection in mixed

---
 src/realm/bplustree.cpp | 23 +++++++++++++++++++++--
 src/realm/cluster.cpp   | 12 +++++++++++-
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/src/realm/bplustree.cpp b/src/realm/bplustree.cpp
index 2ebb9097ea8..c381d978093 100644
--- a/src/realm/bplustree.cpp
+++ b/src/realm/bplustree.cpp
@@ -867,8 +867,27 @@ ref_type BPlusTreeBase::typed_write(ref_type ref, _impl::ArrayWriterBase& out, A
     }
     else {
         if (node.has_refs()) {
-            // this should be extended to handle Mixed....
-            return node.write(out, deep, only_modified, false); // unknown substructure, don't compress
+            // TODO: handle collection in mixed here. This is breaking..
+            Array written_node(Allocator::get_default());
+            written_node.create(NodeHeader::type_InnerBptreeNode, false, node.size());
+            for (unsigned j = 0; j < node.size(); ++j) {
+                RefOrTagged rot = node.get_as_ref_or_tagged(j);
+                if (rot.is_ref() && rot.get_as_ref()) {
+                    // it should/could only be a nested collection
+                    compress = true;
+                    written_node.set_as_ref(j, BPlusTreeBase::typed_write(rot.get_as_ref(), out, alloc, col_type,
+                                                                          deep, only_modified, compress));
+                }
+                else {
+                    Array a(alloc);
+                    a.init_from_ref(rot.get_as_ref());
+                    written_node.set_as_ref(j, a.write(out, deep, only_modified, false));
+                }
+            }
+            auto written_ref = written_node.write(out, false, false, false);
+            written_node.destroy();
+            return written_ref;
+            // return node.write(out, deep, only_modified, false); // unknown substructure, don't compress
         }
         else {
             return node.write(out, false, only_modified, compress); // leaf array - do compress
diff --git a/src/realm/cluster.cpp b/src/realm/cluster.cpp
index 404bcf8fdf1..d940e870cd0 100644
--- a/src/realm/cluster.cpp
+++ b/src/realm/cluster.cpp
@@ -1678,7 +1678,17 @@ ref_type Cluster::typed_write(ref_type ref, _impl::ArrayWriterBase& out, const T
 
                         const auto do_compress = (i < 3) ? true : false;
                         if (i == 4) {
-                            // TODO: handle collections in mixed
+                            // TODO this is not working...
+                            bool compress = true;
+                            auto bptree_rot = leaf.get_as_ref_or_tagged(i);
+                            if (bptree_rot.is_ref() && bptree_rot.get_as_ref()) {
+                                written_leaf.set_as_ref(i, BPlusTreeBase::typed_write(bptree_rot.get_as_ref(), out,
+                                                                                      m_alloc, col_type, deep,
+                                                                                      only_modified, compress));
+                            }
+                            else {
+                                written_leaf.set(i, bptree_rot);
+                            }
                         }
                         // compress only mixed arrays that are integers. skip all the rest for now.
                         written_leaf.set_as_ref(