diff --git a/swh/scanner/cli.py b/swh/scanner/cli.py
--- a/swh/scanner/cli.py
+++ b/swh/scanner/cli.py
@@ -137,9 +137,9 @@
 @click.option(
     "-p",
     "--policy",
-    default="bfs",
+    default="auto",
     show_default=True,
-    type=click.Choice(["bfs", "filepriority", "dirpriority"]),
+    type=click.Choice(["auto", "bfs", "filepriority", "dirpriority"]),
     help="The scan policy.",
 )
 @click.pass_context
diff --git a/swh/scanner/policy.py b/swh/scanner/policy.py
--- a/swh/scanner/policy.py
+++ b/swh/scanner/policy.py
@@ -16,6 +16,8 @@
 from .data import MerkleNodeInfo
 from .exceptions import error_response
 
+QUERY_LIMIT = 1000
+
 
 async def swhids_discovery(
     swhids: List[str], session: aiohttp.ClientSession, api_url: str,
@@ -38,12 +40,11 @@
 
     """
     endpoint = api_url + "known/"
-    chunk_size = 1000
     requests = []
 
     def get_chunk(swhids):
-        for i in range(0, len(swhids), chunk_size):
-            yield swhids[i : i + chunk_size]
+        for i in range(0, len(swhids), QUERY_LIMIT):
+            yield swhids[i : i + QUERY_LIMIT]
 
     async def make_request(swhids):
         async with session.post(endpoint, json=swhids) as resp:
@@ -52,7 +53,7 @@
 
             return await resp.json()
 
-    if len(swhids) > chunk_size:
+    if len(swhids) > QUERY_LIMIT:
         for swhids_chunk in get_chunk(swhids):
             requests.append(asyncio.create_task(make_request(swhids_chunk)))
 
@@ -248,3 +249,15 @@
         for _, node in list(dir_.items()):
             if node.object_type == CONTENT:
                 yield node
+
+
+class QueryAll(Policy):
+    @no_type_check
+    async def run(
+        self, session: aiohttp.ClientSession, api_url: str,
+    ):
+        all_nodes = [node for node in self.source_tree.iter_tree()]
+        all_swhids = [str(node.swhid()) for node in all_nodes]
+        swhids_res = await swhids_discovery(all_swhids, session, api_url)
+        for node in all_nodes:
+            self.data[node.swhid()]["known"] = swhids_res[str(node.swhid())]["known"]
diff --git a/swh/scanner/scanner.py b/swh/scanner/scanner.py
--- a/swh/scanner/scanner.py
+++ b/swh/scanner/scanner.py
@@ -13,7 +13,7 @@
 
 from .data import MerkleNodeInfo
 from .output import Output
-from .policy import DirectoryPriority, FilePriority, LazyBFS
+from .policy import QUERY_LIMIT, DirectoryPriority, FilePriority, LazyBFS, QueryAll
 
 
 async def run(config: Dict[str, Any], policy) -> None:
@@ -35,8 +35,18 @@
         await policy.run(session, api_url)
 
 
+def source_size(source_tree: Directory):
+    return len([n for n in source_tree.iter_tree(dedup=False)])
+
+
 def get_policy_obj(source_tree: Directory, nodes_data: MerkleNodeInfo, policy: str):
-    if policy == "bfs":
+    if policy == "auto":
+        return (
+            QueryAll(source_tree, nodes_data)
+            if source_size(source_tree) <= QUERY_LIMIT
+            else LazyBFS(source_tree, nodes_data)
+        )
+    elif policy == "bfs":
         return LazyBFS(source_tree, nodes_data)
     elif policy == "filepriority":
         return FilePriority(source_tree, nodes_data)
diff --git a/swh/scanner/tests/test_scanner.py b/swh/scanner/tests/test_scanner.py
--- a/swh/scanner/tests/test_scanner.py
+++ b/swh/scanner/tests/test_scanner.py
@@ -7,8 +7,8 @@
 import pytest
 
 from swh.scanner.data import MerkleNodeInfo
-from swh.scanner.policy import DirectoryPriority, FilePriority, LazyBFS
-from swh.scanner.scanner import run
+from swh.scanner.policy import DirectoryPriority, FilePriority, LazyBFS, QueryAll
+from swh.scanner.scanner import get_policy_obj, run
 
 from .data import unknown_swhids
 
@@ -18,6 +18,10 @@
     assert not app.debug
 
 
+def test_get_policy_obj_auto(source_tree, nodes_data):
+    assert isinstance(get_policy_obj(source_tree, nodes_data, "auto"), QueryAll)
+
+
 def test_scanner_result_bfs(live_server, event_loop, source_tree):
     api_url = url_for("index", _external=True)
     config = {"web-api": {"url": api_url, "auth-token": None}}