diff --git a/sql/upgrades/168.sql b/sql/upgrades/168.sql
new file mode 100644
--- /dev/null
+++ b/sql/upgrades/168.sql
@@ -0,0 +1,24 @@
+-- SWH DB schema upgrade
+-- from_version: 167
+-- to_version: 168
+-- description: add raw_extrinsic_metadata.id
+
+insert into dbversion(version, release, description)
+  values(168, now(), 'Work In Progress');
+
+-- 1. add the 'id' column
+
+alter table raw_extrinsic_metadata
+  add column id sha1_git;
+
+-- 2. restart swh-storage, so that it starts writing the id (but does not read it)
+
+-- 3. run swh storage migrate-168
+
+-- 4. make the id column not null, and index it
+
+alter table raw_extrinsic_metadata
+  alter column id set not null;
+
+create unique index concurrently raw_extrinsic_metadata_pkey on raw_extrinsic_metadata(id);
+alter table raw_extrinsic_metadata add primary key using index raw_extrinsic_metadata_pkey;
diff --git a/swh/storage/cli.py b/swh/storage/cli.py
--- a/swh/storage/cli.py
+++ b/swh/storage/cli.py
@@ -201,6 +201,88 @@
         client.close()
 
 
+@storage.command()
+@click.pass_context
+def migrate_168(ctx):
+    """Fills the 'id' column of raw_extrinsic_metadata in a postgresql backend.
+
+    Uses the journal as input (instead of SELECT) so it is parallelizable and
+    stop/resumable.
+    """
+    import psycopg2.extras
+
+    from swh.journal.client import get_journal_client
+    from swh.model.hashutil import hash_to_bytes
+    from swh.model.identifiers import raw_extrinsic_metadata_identifier
+    from swh.storage import get_storage
+    from swh.storage.postgresql.storage import Storage as PostgresqlStorage
+
+    ensure_check_config(ctx.obj["config"], ctx.obj["check_config"], "write")
+
+    conf = ctx.obj["config"]
+    storage = get_storage(**conf.pop("storage"))
+
+    if not isinstance(storage, PostgresqlStorage):
+        raise click.Error("storage must has 'cls: local'.")
+
+    conn = storage.db.conn
+
+    client_cfg = conf.pop("journal_client")
+    try:
+        client = get_journal_client(**client_cfg)
+    except ValueError as exc:
+        ctx.fail(exc)
+
+    query = """
+        UPDATE raw_extrinsic_metadata
+        SET id=?
+        FROM authority, fetcher
+        WHERE
+            authority.id=raw_extrinsic_metadata.authority_id
+            fetcher.id=raw_extrinsic_metadata.fetcher_id
+            AND authority.type=?
+            AND authority.url=?
+            AND discovery_date=?
+            AND fetcher.name=?
+            AND fetcher.version=?
+    """
+
+    def worker_fn(all_objects):
+        assert set(all_objects) == {"raw_extrinsic_metadata"}
+        rows = []
+        for obj in all_objects["raw_extrinsic_metadata"]:
+            rows.append(
+                (
+                    hash_to_bytes(raw_extrinsic_metadata_identifier(obj)),
+                    obj["target"],
+                    obj["authority"]["type"],
+                    obj["authority"]["url"],
+                    obj["discovery_date"],
+                    obj["fetcher"]["name"],
+                    obj["fetcher"]["version"],
+                )
+            )
+
+        with conn.cursor() as cur:
+            psycopg2.extras.execute_batch(cur, query, rows)
+
+        conn.commit()
+
+    if notify:
+        notify("READY=1")
+
+    try:
+        client.process(worker_fn)
+    except KeyboardInterrupt:
+        ctx.exit(0)
+    else:
+        print("Done.")
+    finally:
+        if notify:
+            notify("STOPPING=1")
+        client.close()
+
+
 def ensure_check_config(storage_cfg: Dict, check_config: Optional[str], default: str):
     """Helper function to inject the setting of check_config option in the storage config
     dict according to the expected default value (default value depends on the command,
diff --git a/swh/storage/postgresql/db.py b/swh/storage/postgresql/db.py
--- a/swh/storage/postgresql/db.py
+++ b/swh/storage/postgresql/db.py
@@ -28,7 +28,7 @@
 
     """
 
-    current_version = 166
+    current_version = 168
 
     def mktemp_dir_entry(self, entry_type, cur=None):
         self._cursor(cur).execute(
@@ -1136,6 +1136,7 @@
     """The list of context columns for all artifact types."""
 
     _raw_extrinsic_metadata_insert_cols = [
+        "id",
         "type",
         "target",
         "authority_id",
@@ -1184,6 +1185,7 @@
 
     def raw_extrinsic_metadata_add(
         self,
+        id: bytes,
         type: str,
         target: str,
         discovery_date: datetime.datetime,
@@ -1202,6 +1204,7 @@
     ):
         query = self._raw_extrinsic_metadata_insert_query
         args: Dict[str, Any] = dict(
+            id=id,
             type=type,
             target=target,
             authority_id=authority_id,
diff --git a/swh/storage/postgresql/storage.py b/swh/storage/postgresql/storage.py
--- a/swh/storage/postgresql/storage.py
+++ b/swh/storage/postgresql/storage.py
@@ -1256,6 +1256,7 @@
             fetcher_id = self._get_fetcher_id(metadata_entry.fetcher, db, cur)
 
             db.raw_extrinsic_metadata_add(
+                id=metadata_entry.id,
                 type=metadata_entry.type.value,
                 target=str(metadata_entry.target),
                 discovery_date=metadata_entry.discovery_date,
diff --git a/swh/storage/sql/30-schema.sql b/swh/storage/sql/30-schema.sql
--- a/swh/storage/sql/30-schema.sql
+++ b/swh/storage/sql/30-schema.sql
@@ -17,7 +17,7 @@
 
 -- latest schema version
 insert into dbversion(version, release, description)
-      values(166, now(), 'Work In Progress');
+      values(168, now(), 'Work In Progress');
 
 -- a SHA1 checksum
 create domain sha1 as bytea check (length(value) = 20);
@@ -430,6 +430,8 @@
 -- Extrinsic metadata on a DAG objects and origins.
 create table raw_extrinsic_metadata
 (
+  id             sha1_git      not null,
+
   type           text          not null,
   target         text          not null,
 
diff --git a/swh/storage/sql/60-indexes.sql b/swh/storage/sql/60-indexes.sql
--- a/swh/storage/sql/60-indexes.sql
+++ b/swh/storage/sql/60-indexes.sql
@@ -264,6 +264,10 @@
 
 
 -- raw_extrinsic_metadata
+
+create unique index concurrently raw_extrinsic_metadata_pkey on raw_extrinsic_metadata(id);
+alter table raw_extrinsic_metadata add primary key using index raw_extrinsic_metadata_pkey;
+
 create unique index concurrently raw_extrinsic_metadata_content_authority_date_fetcher on raw_extrinsic_metadata(target, authority_id, discovery_date, fetcher_id);
 
 \if :dbflavor_default