WIP - Add support for col-level tt queries

internal/db/fetcher/versioned.go

@@ -326,6 +326,12 @@ func (vf *VersionedFetcher) merge(c cid.Cid) error {
 
 	var mcrdt merklecrdt.MerkleCRDT
 	switch {
+	case block.Delta.IsCollection():
+		mcrdt = merklecrdt.NewMerkleCollection(
+			vf.store,
+			keys.CollectionSchemaVersionKey{},
+			keys.NewHeadstoreColKey(vf.col.Description().RootID),
+		)
 	case block.Delta.IsComposite():
 		mcrdt = merklecrdt.NewMerkleCompositeDAG(
 			vf.store,

tests/integration/query/simple/with_cid_branchable_test.go

@@ -0,0 +1,59 @@
+// Copyright 2024 Democratized Data Foundation
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package simple
+
+import (
+	"testing"
+
+	testUtils "github.com/sourcenetwork/defradb/tests/integration"
+)
+
+func TestQuerySimpleWithCidOfBranchableCollection_FirstCid(t *testing.T) {
+	test := testUtils.TestCase{
+		Actions: []any{
+			testUtils.SchemaUpdate{
+				Schema: `
+					type Users @branchable {
+						name: String
+					}
+				`,
+			},
+			testUtils.CreateDoc{
+				Doc: `{
+					"name": "Fred"
+				}`,
+			},
+			testUtils.CreateDoc{
+				Doc: `{
+					"name": "John"
+				}`,
+			},
+			testUtils.Request{ // bafyreiewwsnu2ld5qlntamdm77ayb7xtmxz3p5difvaaakaome7zbtpo4u
+				Request: `query {
+					Users (
+							cid: "bafyreiewwsnu2ld5qlntamdm77ayb7xtmxz3p5difvaaakaome7zbtpo4u"
+						) {
+						name
+					}
+				}`,
+				Results: map[string]any{
+					"Users": []map[string]any{
+						{
+							"name": "Fred",
+						},
+					},
+				},
+			},
+		},
+	}
+
+	testUtils.ExecuteTestCase(t, test)
+}