diff --git a/edb/pgsql/patches.py b/edb/pgsql/patches.py
index d9115bd86a6..4307e8cdda0 100644
--- a/edb/pgsql/patches.py
+++ b/edb/pgsql/patches.py
@@ -102,4 +102,6 @@ def _setup_patches(patches: list[tuple[str, str]]) -> list[tuple[str, str]]:
 '''),
     ('edgeql+schema', ''),  # pg_attribute, pg_attribute_ext, edgedbsql.columns
     ('edgeql+schema', ''),  # __type__
+    # === 4.6
+    ('edgeql+schema+globalonly', ''),  # recreate introspection query
 ])
diff --git a/edb/schema/reflection/structure.py b/edb/schema/reflection/structure.py
index a21a1edc277..12ee09a07b4 100644
--- a/edb/schema/reflection/structure.py
+++ b/edb/schema/reflection/structure.py
@@ -30,6 +30,7 @@
 
 from edb.edgeql import qltypes
 
+from edb.schema import constraints as s_constr
 from edb.schema import ddl as s_ddl
 from edb.schema import delta as sd
 from edb.schema import expr as s_expr
@@ -529,7 +530,38 @@ def generate_structure(
                         f'{read_ptr}: {{name, value := .{proxy_link}.id}}'
                     )
 
-                if ptr.issubclass(schema, ordered_link):
+                # HACK: Pre 4.6, we did not correctly populate the
+                # @index linkprop for concrete constraint params,
+                # which can cause migration trouble if they happen to
+                # get read back in the wrong order. We fixed it
+                # forward, but we need to be able to handle cases
+                # where it is still missing, so we read the order out
+                # of the nearest abstract *ancestor*, since abstract
+                # constraint @indexs always got populated properly.
+                if (
+                    sfn == 'params'
+                    and issubclass(py_cls, s_constr.Constraint)
+                ):
+                    read_ptr = '''
+                        params := (select .params {
+                          id,
+                          baseindex := assert_single((
+                            # fetch the first non-concrete ancestor
+                            with anc := (
+                              select schema::Constraint.ancestors[
+                                  is schema::Constraint]
+                              filter .abstract order by @index limit 1
+                            ),
+                            # ... and pull out the index of the matching param
+                            select anc {
+                             params
+                             filter .name = schema::Constraint.params.name
+                            }.params@index
+                          ))
+                        } order by @index ?? .baseindex) { id }
+                    '''
+
+                elif ptr.issubclass(schema, ordered_link):
                     read_ptr = f'{read_ptr} ORDER BY @index'
 
                 read_shape.append(read_ptr)
diff --git a/edb/schema/reflection/writer.py b/edb/schema/reflection/writer.py
index 30c3e83f5f0..fb80509ddde 100644
--- a/edb/schema/reflection/writer.py
+++ b/edb/schema/reflection/writer.py
@@ -299,12 +299,13 @@ def _build_object_mutation_shape(
             # an ObjectKeyDict collection that allow associating objects
             # with arbitrary values (a transposed ObjectDict).
             target_expr = f"""assert_distinct((
-                FOR v IN {{ json_array_unpack(<json>${var_n}) }}
+                FOR v IN {{ enumerate(json_array_unpack(<json>${var_n})) }}
                 UNION (
                     SELECT {target.get_name(schema)} {{
-                        @value := <str>v[1]
+                        @index := v.0,
+                        @value := <str>v.1[1],
                     }}
-                    FILTER .id = <uuid>v[0]
+                    FILTER .id = <uuid>v.1[0]
                 )
             ))"""
             args = props.get('args', [])
diff --git a/tests/test_edgeql_ddl.py b/tests/test_edgeql_ddl.py
index 0e2577e95ae..cfd740616b5 100644
--- a/tests/test_edgeql_ddl.py
+++ b/tests/test_edgeql_ddl.py
@@ -10190,6 +10190,26 @@ async def test_edgeql_ddl_constraint_09(self):
             CREATE TYPE Comment EXTENDING Text;
         """)
 
+        await self.assert_query_result(
+            """
+            select schema::Constraint {
+                name, params: {name, @index} order by @index
+            }
+            filter .name = 'std::max_len_value'
+            and .subject.name = 'body'
+            and .subject[is schema::Pointer].source.name ='default::Text';
+            """,
+            [
+                {
+                    "name": "std::max_len_value",
+                    "params": [
+                        {"name": "__subject__", "@index": 0},
+                        {"name": "max", "@index": 1}
+                    ]
+                }
+            ],
+        )
+
         await self.con.execute("""
             ALTER TYPE Text
                 ALTER PROPERTY body