diff --git a/conftest.py b/conftest.py
new file mode 100644
--- /dev/null
+++ b/conftest.py
@@ -0,0 +1 @@
+pytest_plugins = ["swh.storage.pytest_plugin"]
\ No newline at end of file
diff --git a/mypy.ini b/mypy.ini
--- a/mypy.ini
+++ b/mypy.ini
@@ -11,5 +11,8 @@
 [mypy-pytest.*]
 ignore_missing_imports = True
 
+[mypy-psycopg2.*]
+ignore_missing_imports = True
+
 # [mypy-add_your_lib_here.*]
 # ignore_missing_imports = True
diff --git a/requirements-swh.txt b/requirements-swh.txt
--- a/requirements-swh.txt
+++ b/requirements-swh.txt
@@ -1,2 +1,3 @@
 # Add here internal Software Heritage dependencies, one per line.
 swh.core[http] >= 0.3
+swh.model >= 0.9.0
diff --git a/requirements.txt b/requirements.txt
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,11 @@
-# Add here external Python modules dependencies, one per line. Module names
-# should match https://pypi.python.org/pypi names. For the full spec or
-# dependency lines, see https://pip.readthedocs.org/en/1.1/requirements.html
-
+attrs==20.3.0
+attrs-strict==0.2.0
+Deprecated==1.2.10
+hypothesis==5.49.0
+iso8601==0.1.13
+psycopg2==2.8.6
+python-dateutil==2.8.1
+six==1.15.0
+sortedcontainers==2.3.0
+typing-extensions==3.7.4.3
+wrapt==1.12.1
diff --git a/swh/clearlydefined/mapping_utils.py b/swh/clearlydefined/mapping_utils.py
new file mode 100644
--- /dev/null
+++ b/swh/clearlydefined/mapping_utils.py
@@ -0,0 +1,23 @@
+# Copyright (C) 2017-2020  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU Affero General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+import psycopg2
+import swh.model.hashutil
+
+
+def map_sha1_with_swhid(sha1, dsn):
+    if not sha1:
+        return None
+    read_connection = psycopg2.connect(dsn=dsn)
+    cur = read_connection.cursor()
+    sha1 = swh.model.hashutil.hash_to_hex(sha1)
+    sha1 = "\\x{sha1}".format(sha1=sha1)
+    cur.execute("SELECT sha1_git FROM content where sha1= %s;", (sha1,))
+    sha1_git = cur.fetchall()
+    if len(sha1_git) == 0:
+        return None
+    sha1_git = swh.model.hashutil.hash_to_hex(sha1_git[0][0])
+    swh_id = "swh:1:cnt:{sha1_git}".format(sha1_git=sha1_git)
+    return swh_id
diff --git a/swh/clearlydefined/tests/test_mapping.py b/swh/clearlydefined/tests/test_mapping.py
new file mode 100644
--- /dev/null
+++ b/swh/clearlydefined/tests/test_mapping.py
@@ -0,0 +1,22 @@
+from swh.clearlydefined.mapping_utils import map_sha1_with_swhid
+import psycopg2
+
+
+def test_mapping(swh_storage_backend_config):
+    dsn = swh_storage_backend_config["db"]
+    read_connection = psycopg2.connect(dsn=dsn)
+    cur = read_connection.cursor()
+    sha1_byte = "\\xa6628c8a4fbc08c29b8472e2222975e5b9918131"
+    sha1_git_byte = "\\xe103b11cbfecbc116dacbb1f9ab2a02176092a32"
+    sha256_byte = "\\x6ac599151a7aaa8ca5d38dc5bb61b49193a3cadc1ed33de5a57e4d1ecc53c846"
+    blake2s256_byte = "\\xc509b320abede3580bb1de75a0efa09ba7416db9c8de845a4e1b4317c0b8a8d9"
+    length = 717
+    cur.execute(
+        "INSERT INTO content (sha1, sha1_git, sha256, blake2s256, length) VALUES (%s,%s,%s,%s,%s);",
+        (sha1_byte, sha1_git_byte, sha256_byte, blake2s256_byte, length),
+    )
+    read_connection.commit()
+    sha1 = "a6628c8a4fbc08c29b8472e2222975e5b9918131"
+    assert "swh:1:cnt:e103b11cbfecbc116dacbb1f9ab2a02176092a32" == map_sha1_with_swhid(
+        sha1=sha1, dsn=dsn
+    )