diff --git a/requirements.txt b/requirements.txt
index c712cdd2..619b1325 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,9 +1,10 @@
 click
 flask
 psycopg2
 vcversioner
 aiohttp
 tenacity
 cassandra-driver >= 3.19.0, != 3.21.0
 deprecated
 typing-extensions
+mypy_extensions
diff --git a/swh/storage/cassandra/cql.py b/swh/storage/cassandra/cql.py
index 5f216304..e10e19c7 100644
--- a/swh/storage/cassandra/cql.py
+++ b/swh/storage/cassandra/cql.py
@@ -1,1017 +1,1034 @@
 # Copyright (C) 2019-2020  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import dataclasses
 import datetime
 import functools
 import logging
 import random
 from typing import (
     Any,
     Callable,
     Dict,
     Iterable,
     Iterator,
     List,
     Optional,
     Tuple,
     Type,
     TypeVar,
 )
 
 from cassandra import CoordinationFailure
 from cassandra.cluster import Cluster, EXEC_PROFILE_DEFAULT, ExecutionProfile, ResultSet
 from cassandra.policies import DCAwareRoundRobinPolicy, TokenAwarePolicy
 from cassandra.query import PreparedStatement, BoundStatement, dict_factory
 from tenacity import (
     retry,
     stop_after_attempt,
     wait_random_exponential,
     retry_if_exception_type,
 )
+from mypy_extensions import NamedArg
 
 from swh.model.model import (
     Content,
     SkippedContent,
     Sha1Git,
     TimestampWithTimezone,
     Timestamp,
     Person,
 )
 
 from swh.storage.interface import ListOrder
 
 from .common import TOKEN_BEGIN, TOKEN_END, hash_url, remove_keys
 from .model import (
     BaseRow,
     ContentRow,
     DirectoryEntryRow,
     DirectoryRow,
     MetadataAuthorityRow,
     MetadataFetcherRow,
     ObjectCountRow,
     OriginRow,
     OriginVisitRow,
     OriginVisitStatusRow,
     RawExtrinsicMetadataRow,
     ReleaseRow,
     RevisionParentRow,
     RevisionRow,
     SkippedContentRow,
     SnapshotBranchRow,
     SnapshotRow,
 )
 from .schema import CREATE_TABLES_QUERIES, HASH_ALGORITHMS
 
 
 logger = logging.getLogger(__name__)
 
 
 _execution_profiles = {
     EXEC_PROFILE_DEFAULT: ExecutionProfile(
         load_balancing_policy=TokenAwarePolicy(DCAwareRoundRobinPolicy()),
         row_factory=dict_factory,
     ),
 }
 # Configuration for cassandra-driver's access to servers:
 # * hit the right server directly when sending a query (TokenAwarePolicy),
 # * if there's more than one, then pick one at random that's in the same
 #   datacenter as the client (DCAwareRoundRobinPolicy)
 
 
 def create_keyspace(
     hosts: List[str], keyspace: str, port: int = 9042, *, durable_writes=True
 ):
     cluster = Cluster(hosts, port=port, execution_profiles=_execution_profiles)
     session = cluster.connect()
     extra_params = ""
     if not durable_writes:
         extra_params = "AND durable_writes = false"
     session.execute(
         """CREATE KEYSPACE IF NOT EXISTS "%s"
                        WITH REPLICATION = {
                            'class' : 'SimpleStrategy',
                            'replication_factor' : 1
                        } %s;
                     """
         % (keyspace, extra_params)
     )
     session.execute('USE "%s"' % keyspace)
     for query in CREATE_TABLES_QUERIES:
         session.execute(query)
 
 
-T = TypeVar("T")
+TRet = TypeVar("TRet")
 
 
-def _prepared_statement(query: str) -> Callable[[Callable[..., T]], Callable[..., T]]:
+def _prepared_statement(
+    query: str,
+) -> Callable[[Callable[..., TRet]], Callable[..., TRet]]:
     """Returns a decorator usable on methods of CqlRunner, to
     inject them with a 'statement' argument, that is a prepared
     statement corresponding to the query.
 
     This only works on methods of CqlRunner, as preparing a
     statement requires a connection to a Cassandra server."""
 
     def decorator(f):
         @functools.wraps(f)
-        def newf(self, *args, **kwargs) -> T:
+        def newf(self, *args, **kwargs) -> TRet:
             if f.__name__ not in self._prepared_statements:
                 statement: PreparedStatement = self._session.prepare(query)
                 self._prepared_statements[f.__name__] = statement
             return f(
                 self, *args, **kwargs, statement=self._prepared_statements[f.__name__]
             )
 
         return newf
 
     return decorator
 
 
-def _prepared_insert_statement(table_name: str, columns: List[str]):
+TArg = TypeVar("TArg")
+TSelf = TypeVar("TSelf")
+
+
+def _prepared_insert_statement(
+    table_name: str, columns: List[str]
+) -> Callable[
+    [Callable[[TSelf, TArg, NamedArg(Any, "statement")], TRet]],  # noqa
+    Callable[[TSelf, TArg], TRet],
+]:
     """Shorthand for using `_prepared_statement` for `INSERT INTO`
     statements."""
     return _prepared_statement(
         "INSERT INTO %s (%s) VALUES (%s)"
         % (table_name, ", ".join(columns), ", ".join("?" for _ in columns),)
     )
 
 
-def _prepared_exists_statement(table_name: str):
+def _prepared_exists_statement(
+    table_name: str,
+) -> Callable[
+    [Callable[[TSelf, TArg, NamedArg(Any, "statement")], TRet]],  # noqa
+    Callable[[TSelf, TArg], TRet],
+]:
     """Shorthand for using `_prepared_statement` for queries that only
     check which ids in a list exist in the table."""
     return _prepared_statement(f"SELECT id FROM {table_name} WHERE id IN ?")
 
 
 class CqlRunner:
     """Class managing prepared statements and building queries to be sent
     to Cassandra."""
 
     def __init__(self, hosts: List[str], keyspace: str, port: int):
         self._cluster = Cluster(
             hosts, port=port, execution_profiles=_execution_profiles
         )
         self._session = self._cluster.connect(keyspace)
         self._cluster.register_user_type(
             keyspace, "microtimestamp_with_timezone", TimestampWithTimezone
         )
         self._cluster.register_user_type(keyspace, "microtimestamp", Timestamp)
         self._cluster.register_user_type(keyspace, "person", Person)
 
         self._prepared_statements: Dict[str, PreparedStatement] = {}
 
     ##########################
     # Common utility functions
     ##########################
 
     MAX_RETRIES = 3
 
     @retry(
         wait=wait_random_exponential(multiplier=1, max=10),
         stop=stop_after_attempt(MAX_RETRIES),
         retry=retry_if_exception_type(CoordinationFailure),
     )
     def _execute_with_retries(self, statement, args) -> ResultSet:
         return self._session.execute(statement, args, timeout=1000.0)
 
     @_prepared_statement(
         "UPDATE object_count SET count = count + ? "
         "WHERE partition_key = 0 AND object_type = ?"
     )
     def _increment_counter(
         self, object_type: str, nb: int, *, statement: PreparedStatement
     ) -> None:
         self._execute_with_retries(statement, [nb, object_type])
 
     def _add_one(self, statement, object_type: Optional[str], obj: BaseRow) -> None:
         if object_type:
             self._increment_counter(object_type, 1)
         self._execute_with_retries(statement, dataclasses.astuple(obj))
 
     _T = TypeVar("_T", bound=BaseRow)
 
     def _get_random_row(self, row_class: Type[_T], statement) -> Optional[_T]:  # noqa
         """Takes a prepared statement of the form
         "SELECT * FROM <table> WHERE token(<keys>) > ? LIMIT 1"
         and uses it to return a random row"""
         token = random.randint(TOKEN_BEGIN, TOKEN_END)
         rows = self._execute_with_retries(statement, [token])
         if not rows:
             # There are no row with a greater token; wrap around to get
             # the row with the smallest token
             rows = self._execute_with_retries(statement, [TOKEN_BEGIN])
         if rows:
             return row_class.from_dict(rows.one())  # type: ignore
         else:
             return None
 
     def _missing(self, statement, ids):
         rows = self._execute_with_retries(statement, [ids])
         found_ids = {row["id"] for row in rows}
         return [id_ for id_ in ids if id_ not in found_ids]
 
     ##########################
     # 'content' table
     ##########################
 
     _content_pk = ["sha1", "sha1_git", "sha256", "blake2s256"]
 
     def _content_add_finalize(self, statement: BoundStatement) -> None:
         """Returned currified by content_add_prepare, to be called when the
         content row should be added to the primary table."""
         self._execute_with_retries(statement, None)
         self._increment_counter("content", 1)
 
     @_prepared_insert_statement("content", ContentRow.cols())
     def content_add_prepare(
         self, content: ContentRow, *, statement
     ) -> Tuple[int, Callable[[], None]]:
         """Prepares insertion of a Content to the main 'content' table.
         Returns a token (to be used in secondary tables), and a function to be
         called to perform the insertion in the main table."""
         statement = statement.bind(dataclasses.astuple(content))
 
         # Type used for hashing keys (usually, it will be
         # cassandra.metadata.Murmur3Token)
         token_class = self._cluster.metadata.token_map.token_class
 
         # Token of the row when it will be inserted. This is equivalent to
         # "SELECT token({', '.join(self._content_pk)}) FROM content WHERE ..."
         # after the row is inserted; but we need the token to insert in the
         # index tables *before* inserting to the main 'content' table
         token = token_class.from_key(statement.routing_key).value
         assert TOKEN_BEGIN <= token <= TOKEN_END
 
         # Function to be called after the indexes contain their respective
         # row
         finalizer = functools.partial(self._content_add_finalize, statement)
 
         return (token, finalizer)
 
     @_prepared_statement(
         "SELECT * FROM content WHERE "
         + " AND ".join(map("%s = ?".__mod__, HASH_ALGORITHMS))
     )
     def content_get_from_pk(
         self, content_hashes: Dict[str, bytes], *, statement
     ) -> Optional[ContentRow]:
         rows = list(
             self._execute_with_retries(
                 statement, [content_hashes[algo] for algo in HASH_ALGORITHMS]
             )
         )
         assert len(rows) <= 1
         if rows:
             return ContentRow(**rows[0])
         else:
             return None
 
     @_prepared_statement(
         "SELECT * FROM content WHERE token(" + ", ".join(_content_pk) + ") = ?"
     )
     def content_get_from_token(self, token, *, statement) -> Iterable[ContentRow]:
         return map(ContentRow.from_dict, self._execute_with_retries(statement, [token]))
 
     @_prepared_statement(
         "SELECT * FROM content WHERE token(%s) > ? LIMIT 1" % ", ".join(_content_pk)
     )
     def content_get_random(self, *, statement) -> Optional[ContentRow]:
         return self._get_random_row(ContentRow, statement)
 
     @_prepared_statement(
         (
             "SELECT token({0}) AS tok, {1} FROM content "
             "WHERE token({0}) >= ? AND token({0}) <= ? LIMIT ?"
         ).format(", ".join(_content_pk), ", ".join(ContentRow.cols()))
     )
     def content_get_token_range(
         self, start: int, end: int, limit: int, *, statement
     ) -> Iterable[Tuple[int, ContentRow]]:
         """Returns an iterable of (token, row)"""
         return (
             (row["tok"], ContentRow.from_dict(remove_keys(row, ("tok",))))
             for row in self._execute_with_retries(statement, [start, end, limit])
         )
 
     ##########################
     # 'content_by_*' tables
     ##########################
 
     @_prepared_statement(
         "SELECT sha1_git AS id FROM content_by_sha1_git WHERE sha1_git IN ?"
     )
     def content_missing_by_sha1_git(
         self, ids: List[bytes], *, statement
     ) -> List[bytes]:
         return self._missing(statement, ids)
 
     def content_index_add_one(self, algo: str, content: Content, token: int) -> None:
         """Adds a row mapping content[algo] to the token of the Content in
         the main 'content' table."""
         query = (
             f"INSERT INTO content_by_{algo} ({algo}, target_token) " f"VALUES (%s, %s)"
         )
         self._execute_with_retries(query, [content.get_hash(algo), token])
 
     def content_get_tokens_from_single_hash(
         self, algo: str, hash_: bytes
     ) -> Iterable[int]:
         assert algo in HASH_ALGORITHMS
         query = f"SELECT target_token FROM content_by_{algo} WHERE {algo} = %s"
         return (
             row["target_token"] for row in self._execute_with_retries(query, [hash_])
         )
 
     ##########################
     # 'skipped_content' table
     ##########################
 
     _skipped_content_pk = ["sha1", "sha1_git", "sha256", "blake2s256"]
     _magic_null_pk = b"<null>"
     """
     NULLs (or all-empty blobs) are not allowed in primary keys; instead use a
     special value that can't possibly be a valid hash.
     """
 
     def _skipped_content_add_finalize(self, statement: BoundStatement) -> None:
         """Returned currified by skipped_content_add_prepare, to be called
         when the content row should be added to the primary table."""
         self._execute_with_retries(statement, None)
         self._increment_counter("skipped_content", 1)
 
     @_prepared_insert_statement("skipped_content", SkippedContentRow.cols())
     def skipped_content_add_prepare(
         self, content, *, statement
     ) -> Tuple[int, Callable[[], None]]:
         """Prepares insertion of a Content to the main 'skipped_content' table.
         Returns a token (to be used in secondary tables), and a function to be
         called to perform the insertion in the main table."""
 
         # Replace NULLs (which are not allowed in the partition key) with
         # an empty byte string
         for key in self._skipped_content_pk:
             if getattr(content, key) is None:
                 setattr(content, key, self._magic_null_pk)
 
         statement = statement.bind(dataclasses.astuple(content))
 
         # Type used for hashing keys (usually, it will be
         # cassandra.metadata.Murmur3Token)
         token_class = self._cluster.metadata.token_map.token_class
 
         # Token of the row when it will be inserted. This is equivalent to
         # "SELECT token({', '.join(self._content_pk)})
         #  FROM skipped_content WHERE ..."
         # after the row is inserted; but we need the token to insert in the
         # index tables *before* inserting to the main 'skipped_content' table
         token = token_class.from_key(statement.routing_key).value
         assert TOKEN_BEGIN <= token <= TOKEN_END
 
         # Function to be called after the indexes contain their respective
         # row
         finalizer = functools.partial(self._skipped_content_add_finalize, statement)
 
         return (token, finalizer)
 
     @_prepared_statement(
         "SELECT * FROM skipped_content WHERE "
         + " AND ".join(map("%s = ?".__mod__, HASH_ALGORITHMS))
     )
     def skipped_content_get_from_pk(
         self, content_hashes: Dict[str, bytes], *, statement
     ) -> Optional[SkippedContentRow]:
         rows = list(
             self._execute_with_retries(
                 statement,
                 [
                     content_hashes[algo] or self._magic_null_pk
                     for algo in HASH_ALGORITHMS
                 ],
             )
         )
         assert len(rows) <= 1
         if rows:
             # TODO: convert _magic_null_pk back to None?
             return SkippedContentRow.from_dict(rows[0])
         else:
             return None
 
     ##########################
     # 'skipped_content_by_*' tables
     ##########################
 
     def skipped_content_index_add_one(
         self, algo: str, content: SkippedContent, token: int
     ) -> None:
         """Adds a row mapping content[algo] to the token of the SkippedContent
         in the main 'skipped_content' table."""
         query = (
             f"INSERT INTO skipped_content_by_{algo} ({algo}, target_token) "
             f"VALUES (%s, %s)"
         )
         self._execute_with_retries(
             query, [content.get_hash(algo) or self._magic_null_pk, token]
         )
 
     ##########################
     # 'revision' table
     ##########################
 
     @_prepared_exists_statement("revision")
     def revision_missing(self, ids: List[bytes], *, statement) -> List[bytes]:
         return self._missing(statement, ids)
 
     @_prepared_insert_statement("revision", RevisionRow.cols())
     def revision_add_one(self, revision: RevisionRow, *, statement) -> None:
         self._add_one(statement, "revision", revision)
 
     @_prepared_statement("SELECT id FROM revision WHERE id IN ?")
     def revision_get_ids(self, revision_ids, *, statement) -> Iterable[int]:
         return (
             row["id"] for row in self._execute_with_retries(statement, [revision_ids])
         )
 
     @_prepared_statement("SELECT * FROM revision WHERE id IN ?")
     def revision_get(self, revision_ids, *, statement) -> Iterable[RevisionRow]:
         return map(
             RevisionRow.from_dict, self._execute_with_retries(statement, [revision_ids])
         )
 
     @_prepared_statement("SELECT * FROM revision WHERE token(id) > ? LIMIT 1")
     def revision_get_random(self, *, statement) -> Optional[RevisionRow]:
         return self._get_random_row(RevisionRow, statement)
 
     ##########################
     # 'revision_parent' table
     ##########################
 
     @_prepared_insert_statement("revision_parent", RevisionParentRow.cols())
     def revision_parent_add_one(
         self, revision_parent: RevisionParentRow, *, statement
     ) -> None:
         self._add_one(statement, None, revision_parent)
 
     @_prepared_statement("SELECT parent_id FROM revision_parent WHERE id = ?")
     def revision_parent_get(
         self, revision_id: Sha1Git, *, statement
     ) -> Iterable[bytes]:
         return (
             row["parent_id"]
             for row in self._execute_with_retries(statement, [revision_id])
         )
 
     ##########################
     # 'release' table
     ##########################
 
     @_prepared_exists_statement("release")
     def release_missing(self, ids: List[bytes], *, statement) -> List[bytes]:
         return self._missing(statement, ids)
 
     @_prepared_insert_statement("release", ReleaseRow.cols())
     def release_add_one(self, release: ReleaseRow, *, statement) -> None:
         self._add_one(statement, "release", release)
 
     @_prepared_statement("SELECT * FROM release WHERE id in ?")
     def release_get(self, release_ids: List[str], *, statement) -> Iterable[ReleaseRow]:
         return map(
             ReleaseRow.from_dict, self._execute_with_retries(statement, [release_ids])
         )
 
     @_prepared_statement("SELECT * FROM release WHERE token(id) > ? LIMIT 1")
     def release_get_random(self, *, statement) -> Optional[ReleaseRow]:
         return self._get_random_row(ReleaseRow, statement)
 
     ##########################
     # 'directory' table
     ##########################
 
     @_prepared_exists_statement("directory")
     def directory_missing(self, ids: List[bytes], *, statement) -> List[bytes]:
         return self._missing(statement, ids)
 
     @_prepared_insert_statement("directory", DirectoryRow.cols())
     def directory_add_one(self, directory: DirectoryRow, *, statement) -> None:
         """Called after all calls to directory_entry_add_one, to
         commit/finalize the directory."""
         self._add_one(statement, "directory", directory)
 
     @_prepared_statement("SELECT * FROM directory WHERE token(id) > ? LIMIT 1")
     def directory_get_random(self, *, statement) -> Optional[DirectoryRow]:
         return self._get_random_row(DirectoryRow, statement)
 
     ##########################
     # 'directory_entry' table
     ##########################
 
     @_prepared_insert_statement("directory_entry", DirectoryEntryRow.cols())
     def directory_entry_add_one(self, entry: DirectoryEntryRow, *, statement) -> None:
         self._add_one(statement, None, entry)
 
     @_prepared_statement("SELECT * FROM directory_entry WHERE directory_id IN ?")
     def directory_entry_get(
         self, directory_ids, *, statement
     ) -> Iterable[DirectoryEntryRow]:
         return map(
             DirectoryEntryRow.from_dict,
             self._execute_with_retries(statement, [directory_ids]),
         )
 
     ##########################
     # 'snapshot' table
     ##########################
 
     @_prepared_exists_statement("snapshot")
     def snapshot_missing(self, ids: List[bytes], *, statement) -> List[bytes]:
         return self._missing(statement, ids)
 
     @_prepared_insert_statement("snapshot", SnapshotRow.cols())
     def snapshot_add_one(self, snapshot: SnapshotRow, *, statement) -> None:
         self._add_one(statement, "snapshot", snapshot)
 
     @_prepared_statement("SELECT * FROM snapshot WHERE id = ?")
     def snapshot_get(self, snapshot_id: Sha1Git, *, statement) -> ResultSet:
         return map(
             SnapshotRow.from_dict, self._execute_with_retries(statement, [snapshot_id])
         )
 
     @_prepared_statement("SELECT * FROM snapshot WHERE token(id) > ? LIMIT 1")
     def snapshot_get_random(self, *, statement) -> Optional[SnapshotRow]:
         return self._get_random_row(SnapshotRow, statement)
 
     ##########################
     # 'snapshot_branch' table
     ##########################
 
     @_prepared_insert_statement("snapshot_branch", SnapshotBranchRow.cols())
     def snapshot_branch_add_one(self, branch: SnapshotBranchRow, *, statement) -> None:
         self._add_one(statement, None, branch)
 
     @_prepared_statement(
         "SELECT ascii_bins_count(target_type) AS counts "
         "FROM snapshot_branch "
         "WHERE snapshot_id = ? "
     )
     def snapshot_count_branches(
         self, snapshot_id: Sha1Git, *, statement
     ) -> Dict[Optional[str], int]:
         """Returns a dictionary from type names to the number of branches
         of that type."""
         row = self._execute_with_retries(statement, [snapshot_id]).one()
         (nb_none, counts) = row["counts"]
         return {None: nb_none, **counts}
 
     @_prepared_statement(
         "SELECT * FROM snapshot_branch WHERE snapshot_id = ? AND name >= ? LIMIT ?"
     )
     def snapshot_branch_get(
         self, snapshot_id: Sha1Git, from_: bytes, limit: int, *, statement
     ) -> Iterable[SnapshotBranchRow]:
         return map(
             SnapshotBranchRow.from_dict,
             self._execute_with_retries(statement, [snapshot_id, from_, limit]),
         )
 
     ##########################
     # 'origin' table
     ##########################
 
     @_prepared_insert_statement("origin", OriginRow.cols())
     def origin_add_one(self, origin: OriginRow, *, statement) -> None:
         self._add_one(statement, "origin", origin)
 
     @_prepared_statement("SELECT * FROM origin WHERE sha1 = ?")
     def origin_get_by_sha1(self, sha1: bytes, *, statement) -> Iterable[OriginRow]:
         return map(OriginRow.from_dict, self._execute_with_retries(statement, [sha1]))
 
     def origin_get_by_url(self, url: str) -> Iterable[OriginRow]:
         return self.origin_get_by_sha1(hash_url(url))
 
     @_prepared_statement(
         f'SELECT token(sha1) AS tok, {", ".join(OriginRow.cols())} '
         f"FROM origin WHERE token(sha1) >= ? LIMIT ?"
     )
     def origin_list(
         self, start_token: int, limit: int, *, statement
     ) -> Iterable[Tuple[int, OriginRow]]:
         """Returns an iterable of (token, origin)"""
         return (
             (row["tok"], OriginRow.from_dict(remove_keys(row, ("tok",))))
             for row in self._execute_with_retries(statement, [start_token, limit])
         )
 
     @_prepared_statement("SELECT * FROM origin")
     def origin_iter_all(self, *, statement) -> Iterable[OriginRow]:
         return map(OriginRow.from_dict, self._execute_with_retries(statement, []))
 
     @_prepared_statement("SELECT next_visit_id FROM origin WHERE sha1 = ?")
     def _origin_get_next_visit_id(self, origin_sha1: bytes, *, statement) -> int:
         rows = list(self._execute_with_retries(statement, [origin_sha1]))
         assert len(rows) == 1  # TODO: error handling
         return rows[0]["next_visit_id"]
 
     @_prepared_statement(
         "UPDATE origin SET next_visit_id=? WHERE sha1 = ? IF next_visit_id=?"
     )
     def origin_generate_unique_visit_id(self, origin_url: str, *, statement) -> int:
         origin_sha1 = hash_url(origin_url)
         next_id = self._origin_get_next_visit_id(origin_sha1)
         while True:
             res = list(
                 self._execute_with_retries(
                     statement, [next_id + 1, origin_sha1, next_id]
                 )
             )
             assert len(res) == 1
             if res[0]["[applied]"]:
                 # No data race
                 return next_id
             else:
                 # Someone else updated it before we did, let's try again
                 next_id = res[0]["next_visit_id"]
                 # TODO: abort after too many attempts
 
         return next_id
 
     ##########################
     # 'origin_visit' table
     ##########################
 
     @_prepared_statement(
         "SELECT * FROM origin_visit WHERE origin = ? AND visit > ? "
         "ORDER BY visit ASC"
     )
     def _origin_visit_get_pagination_asc_no_limit(
         self, origin_url: str, last_visit: int, *, statement
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin_url, last_visit])
 
     @_prepared_statement(
         "SELECT * FROM origin_visit WHERE origin = ? AND visit > ? "
         "ORDER BY visit ASC "
         "LIMIT ?"
     )
     def _origin_visit_get_pagination_asc_limit(
         self, origin_url: str, last_visit: int, limit: int, *, statement
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin_url, last_visit, limit])
 
     @_prepared_statement(
         "SELECT * FROM origin_visit WHERE origin = ? AND visit < ? "
         "ORDER BY visit DESC"
     )
     def _origin_visit_get_pagination_desc_no_limit(
         self, origin_url: str, last_visit: int, *, statement
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin_url, last_visit])
 
     @_prepared_statement(
         "SELECT * FROM origin_visit WHERE origin = ? AND visit < ? "
         "ORDER BY visit DESC "
         "LIMIT ?"
     )
     def _origin_visit_get_pagination_desc_limit(
         self, origin_url: str, last_visit: int, limit: int, *, statement
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin_url, last_visit, limit])
 
     @_prepared_statement(
         "SELECT * FROM origin_visit WHERE origin = ? ORDER BY visit ASC LIMIT ?"
     )
     def _origin_visit_get_no_pagination_asc_limit(
         self, origin_url: str, limit: int, *, statement
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin_url, limit])
 
     @_prepared_statement(
         "SELECT * FROM origin_visit WHERE origin = ? ORDER BY visit ASC "
     )
     def _origin_visit_get_no_pagination_asc_no_limit(
         self, origin_url: str, *, statement
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin_url])
 
     @_prepared_statement(
         "SELECT * FROM origin_visit WHERE origin = ? ORDER BY visit DESC"
     )
     def _origin_visit_get_no_pagination_desc_no_limit(
         self, origin_url: str, *, statement
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin_url])
 
     @_prepared_statement(
         "SELECT * FROM origin_visit WHERE origin = ? ORDER BY visit DESC LIMIT ?"
     )
     def _origin_visit_get_no_pagination_desc_limit(
         self, origin_url: str, limit: int, *, statement
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin_url, limit])
 
     def origin_visit_get(
         self,
         origin_url: str,
         last_visit: Optional[int],
         limit: Optional[int],
         order: ListOrder,
     ) -> Iterable[OriginVisitRow]:
         args: List[Any] = [origin_url]
 
         if last_visit is not None:
             page_name = "pagination"
             args.append(last_visit)
         else:
             page_name = "no_pagination"
 
         if limit is not None:
             limit_name = "limit"
             args.append(limit)
         else:
             limit_name = "no_limit"
 
         method_name = f"_origin_visit_get_{page_name}_{order.value}_{limit_name}"
         origin_visit_get_method = getattr(self, method_name)
         return map(OriginVisitRow.from_dict, origin_visit_get_method(*args))
 
     @_prepared_statement(
         "SELECT * FROM origin_visit_status WHERE origin = ? "
         "AND visit = ? AND date >= ? "
         "ORDER BY date ASC "
         "LIMIT ?"
     )
     def _origin_visit_status_get_with_date_asc_limit(
         self,
         origin: str,
         visit: int,
         date_from: datetime.datetime,
         limit: int,
         *,
         statement,
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin, visit, date_from, limit])
 
     @_prepared_statement(
         "SELECT * FROM origin_visit_status WHERE origin = ? "
         "AND visit = ? AND date <= ? "
         "ORDER BY visit DESC "
         "LIMIT ?"
     )
     def _origin_visit_status_get_with_date_desc_limit(
         self,
         origin: str,
         visit: int,
         date_from: datetime.datetime,
         limit: int,
         *,
         statement,
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin, visit, date_from, limit])
 
     @_prepared_statement(
         "SELECT * FROM origin_visit_status WHERE origin = ? AND visit = ? "
         "ORDER BY visit ASC "
         "LIMIT ?"
     )
     def _origin_visit_status_get_with_no_date_asc_limit(
         self, origin: str, visit: int, limit: int, *, statement
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin, visit, limit])
 
     @_prepared_statement(
         "SELECT * FROM origin_visit_status WHERE origin = ? AND visit = ? "
         "ORDER BY visit DESC "
         "LIMIT ?"
     )
     def _origin_visit_status_get_with_no_date_desc_limit(
         self, origin: str, visit: int, limit: int, *, statement
     ) -> ResultSet:
         return self._execute_with_retries(statement, [origin, visit, limit])
 
     def origin_visit_status_get_range(
         self,
         origin: str,
         visit: int,
         date_from: Optional[datetime.datetime],
         limit: int,
         order: ListOrder,
     ) -> Iterable[OriginVisitStatusRow]:
         args: List[Any] = [origin, visit]
 
         if date_from is not None:
             date_name = "date"
             args.append(date_from)
         else:
             date_name = "no_date"
 
         args.append(limit)
 
         method_name = f"_origin_visit_status_get_with_{date_name}_{order.value}_limit"
         origin_visit_status_get_method = getattr(self, method_name)
         return map(
             OriginVisitStatusRow.from_dict, origin_visit_status_get_method(*args)
         )
 
     @_prepared_insert_statement("origin_visit", OriginVisitRow.cols())
     def origin_visit_add_one(self, visit: OriginVisitRow, *, statement) -> None:
         self._add_one(statement, "origin_visit", visit)
 
     @_prepared_insert_statement("origin_visit_status", OriginVisitStatusRow.cols())
     def origin_visit_status_add_one(
         self, visit_update: OriginVisitStatusRow, *, statement
     ) -> None:
         self._add_one(statement, None, visit_update)
 
     def origin_visit_status_get_latest(
         self, origin: str, visit: int,
     ) -> Optional[OriginVisitStatusRow]:
         """Given an origin visit id, return its latest origin_visit_status
 
          """
         return next(self.origin_visit_status_get(origin, visit), None)
 
     @_prepared_statement(
         "SELECT * FROM origin_visit_status "
         "WHERE origin = ? AND visit = ? "
         "ORDER BY date DESC"
     )
     def origin_visit_status_get(
         self,
         origin: str,
         visit: int,
         allowed_statuses: Optional[List[str]] = None,
         require_snapshot: bool = False,
         *,
         statement,
     ) -> Iterator[OriginVisitStatusRow]:
         """Return all origin visit statuses for a given visit
 
         """
         return map(
             OriginVisitStatusRow.from_dict,
             self._execute_with_retries(statement, [origin, visit]),
         )
 
     @_prepared_statement("SELECT * FROM origin_visit WHERE origin = ? AND visit = ?")
     def origin_visit_get_one(
         self, origin_url: str, visit_id: int, *, statement
     ) -> Optional[OriginVisitRow]:
         # TODO: error handling
         rows = list(self._execute_with_retries(statement, [origin_url, visit_id]))
         if rows:
             return OriginVisitRow.from_dict(rows[0])
         else:
             return None
 
     @_prepared_statement("SELECT * FROM origin_visit WHERE origin = ?")
     def origin_visit_get_all(
         self, origin_url: str, *, statement
     ) -> Iterable[OriginVisitRow]:
         return map(
             OriginVisitRow.from_dict,
             self._execute_with_retries(statement, [origin_url]),
         )
 
     @_prepared_statement("SELECT * FROM origin_visit WHERE token(origin) >= ?")
     def _origin_visit_iter_from(
         self, min_token: int, *, statement
     ) -> Iterable[OriginVisitRow]:
         return map(
             OriginVisitRow.from_dict, self._execute_with_retries(statement, [min_token])
         )
 
     @_prepared_statement("SELECT * FROM origin_visit WHERE token(origin) < ?")
     def _origin_visit_iter_to(
         self, max_token: int, *, statement
     ) -> Iterable[OriginVisitRow]:
         return map(
             OriginVisitRow.from_dict, self._execute_with_retries(statement, [max_token])
         )
 
     def origin_visit_iter(self, start_token: int) -> Iterator[OriginVisitRow]:
         """Returns all origin visits in order from this token,
         and wraps around the token space."""
         yield from self._origin_visit_iter_from(start_token)
         yield from self._origin_visit_iter_to(start_token)
 
     ##########################
     # 'metadata_authority' table
     ##########################
 
     @_prepared_insert_statement("metadata_authority", MetadataAuthorityRow.cols())
     def metadata_authority_add(self, authority: MetadataAuthorityRow, *, statement):
         self._add_one(statement, None, authority)
 
     @_prepared_statement("SELECT * from metadata_authority WHERE type = ? AND url = ?")
     def metadata_authority_get(
         self, type, url, *, statement
     ) -> Optional[MetadataAuthorityRow]:
         rows = list(self._execute_with_retries(statement, [type, url]))
         if rows:
             return MetadataAuthorityRow.from_dict(rows[0])
         else:
             return None
 
     ##########################
     # 'metadata_fetcher' table
     ##########################
 
     @_prepared_insert_statement("metadata_fetcher", MetadataFetcherRow.cols())
     def metadata_fetcher_add(self, fetcher, *, statement):
         self._add_one(statement, None, fetcher)
 
     @_prepared_statement(
         "SELECT * from metadata_fetcher WHERE name = ? AND version = ?"
     )
     def metadata_fetcher_get(
         self, name, version, *, statement
     ) -> Optional[MetadataFetcherRow]:
         rows = list(self._execute_with_retries(statement, [name, version]))
         if rows:
             return MetadataFetcherRow.from_dict(rows[0])
         else:
             return None
 
     #########################
     # 'raw_extrinsic_metadata' table
     #########################
 
     @_prepared_insert_statement(
         "raw_extrinsic_metadata", RawExtrinsicMetadataRow.cols()
     )
     def raw_extrinsic_metadata_add(self, raw_extrinsic_metadata, *, statement):
         self._add_one(statement, None, raw_extrinsic_metadata)
 
     @_prepared_statement(
         "SELECT * from raw_extrinsic_metadata "
         "WHERE id=? AND authority_url=? AND discovery_date>? AND authority_type=?"
     )
     def raw_extrinsic_metadata_get_after_date(
         self,
         id: str,
         authority_type: str,
         authority_url: str,
         after: datetime.datetime,
         *,
         statement,
     ) -> Iterable[RawExtrinsicMetadataRow]:
         return map(
             RawExtrinsicMetadataRow.from_dict,
             self._execute_with_retries(
                 statement, [id, authority_url, after, authority_type]
             ),
         )
 
     @_prepared_statement(
         "SELECT * from raw_extrinsic_metadata "
         "WHERE id=? AND authority_type=? AND authority_url=? "
         "AND (discovery_date, fetcher_name, fetcher_version) > (?, ?, ?)"
     )
     def raw_extrinsic_metadata_get_after_date_and_fetcher(
         self,
         id: str,
         authority_type: str,
         authority_url: str,
         after_date: datetime.datetime,
         after_fetcher_name: str,
         after_fetcher_version: str,
         *,
         statement,
     ) -> Iterable[RawExtrinsicMetadataRow]:
         return map(
             RawExtrinsicMetadataRow.from_dict,
             self._execute_with_retries(
                 statement,
                 [
                     id,
                     authority_type,
                     authority_url,
                     after_date,
                     after_fetcher_name,
                     after_fetcher_version,
                 ],
             ),
         )
 
     @_prepared_statement(
         "SELECT * from raw_extrinsic_metadata "
         "WHERE id=? AND authority_url=? AND authority_type=?"
     )
     def raw_extrinsic_metadata_get(
         self, id: str, authority_type: str, authority_url: str, *, statement
     ) -> Iterable[RawExtrinsicMetadataRow]:
         return map(
             RawExtrinsicMetadataRow.from_dict,
             self._execute_with_retries(statement, [id, authority_url, authority_type]),
         )
 
     ##########################
     # Miscellaneous
     ##########################
 
     @_prepared_statement("SELECT uuid() FROM revision LIMIT 1;")
     def check_read(self, *, statement):
         self._execute_with_retries(statement, [])
 
     @_prepared_statement("SELECT * FROM object_count WHERE partition_key=0")
     def stat_counters(self, *, statement) -> ResultSet:
         return map(ObjectCountRow.from_dict, self._execute_with_retries(statement, []))
diff --git a/swh/storage/cassandra/storage.py b/swh/storage/cassandra/storage.py
index f074a62b..ce2ab783 100644
--- a/swh/storage/cassandra/storage.py
+++ b/swh/storage/cassandra/storage.py
@@ -1,1299 +1,1311 @@
 # Copyright (C) 2019-2020  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import base64
 import datetime
 import itertools
 import json
 import random
 import re
-from typing import Any, Dict, List, Iterable, Optional, Set, Tuple, Union
+from typing import Any, Callable, Dict, List, Iterable, Optional, Set, Tuple, Union
 
 import attr
 
 from swh.core.api.serializers import msgpack_loads, msgpack_dumps
 from swh.model.identifiers import parse_swhid, SWHID
 from swh.model.hashutil import DEFAULT_ALGORITHMS
 from swh.model.model import (
     Revision,
     Release,
     Directory,
     DirectoryEntry,
     Content,
     SkippedContent,
     OriginVisit,
     OriginVisitStatus,
     Snapshot,
     SnapshotBranch,
     TargetType,
     Origin,
     MetadataAuthority,
     MetadataAuthorityType,
     MetadataFetcher,
     MetadataTargetType,
     RawExtrinsicMetadata,
     Sha1Git,
 )
 from swh.storage.interface import (
     ListOrder,
     PagedResult,
     PartialBranches,
     Sha1,
     VISIT_STATUSES,
 )
 from swh.storage.objstorage import ObjStorage
 from swh.storage.writer import JournalWriter
 from swh.storage.utils import map_optional, now
 
 from ..exc import StorageArgumentException, HashCollision
 from .common import TOKEN_BEGIN, TOKEN_END, hash_url, remove_keys
 from . import converters
 from .cql import CqlRunner
 from .schema import HASH_ALGORITHMS
 from .model import (
     ContentRow,
     DirectoryEntryRow,
     DirectoryRow,
     MetadataAuthorityRow,
     MetadataFetcherRow,
     OriginRow,
     OriginVisitRow,
     RawExtrinsicMetadataRow,
     RevisionParentRow,
     SkippedContentRow,
     SnapshotBranchRow,
     SnapshotRow,
 )
 
 
 # Max block size of contents to return
 BULK_BLOCK_CONTENT_LEN_MAX = 10000
 
 
 class CassandraStorage:
     def __init__(self, hosts, keyspace, objstorage, port=9042, journal_writer=None):
-        self._cql_runner = CqlRunner(hosts, keyspace, port)
-        self.journal_writer = JournalWriter(journal_writer)
-        self.objstorage = ObjStorage(objstorage)
+        self._cql_runner: CqlRunner = CqlRunner(hosts, keyspace, port)
+        self.journal_writer: JournalWriter = JournalWriter(journal_writer)
+        self.objstorage: ObjStorage = ObjStorage(objstorage)
 
     def check_config(self, *, check_write: bool) -> bool:
         self._cql_runner.check_read()
 
         return True
 
     def _content_get_from_hash(self, algo, hash_) -> Iterable:
         """From the name of a hash algorithm and a value of that hash,
         looks up the "hash -> token" secondary table (content_by_{algo})
         to get tokens.
         Then, looks up the main table (content) to get all contents with
         that token, and filters out contents whose hash doesn't match."""
         found_tokens = self._cql_runner.content_get_tokens_from_single_hash(algo, hash_)
 
         for token in found_tokens:
+            assert isinstance(token, int), found_tokens
             # Query the main table ('content').
             res = self._cql_runner.content_get_from_token(token)
 
             for row in res:
                 # re-check the the hash (in case of murmur3 collision)
                 if getattr(row, algo) == hash_:
                     yield row
 
     def _content_add(self, contents: List[Content], with_data: bool) -> Dict:
         # Filter-out content already in the database.
         contents = [
             c for c in contents if not self._cql_runner.content_get_from_pk(c.to_dict())
         ]
 
         self.journal_writer.content_add(contents)
 
         if with_data:
             # First insert to the objstorage, if the endpoint is
             # `content_add` (as opposed to `content_add_metadata`).
             # TODO: this should probably be done in concurrently to inserting
             # in index tables (but still before the main table; so an entry is
             # only added to the main table after everything else was
             # successfully inserted.
             summary = self.objstorage.content_add(
                 c for c in contents if c.status != "absent"
             )
             content_add_bytes = summary["content:add:bytes"]
 
         content_add = 0
         for content in contents:
             content_add += 1
 
             # Check for sha1 or sha1_git collisions. This test is not atomic
             # with the insertion, so it won't detect a collision if both
             # contents are inserted at the same time, but it's good enough.
             #
             # The proper way to do it would probably be a BATCH, but this
             # would be inefficient because of the number of partitions we
             # need to affect (len(HASH_ALGORITHMS)+1, which is currently 5)
             for algo in {"sha1", "sha1_git"}:
                 collisions = []
                 # Get tokens of 'content' rows with the same value for
                 # sha1/sha1_git
                 rows = self._content_get_from_hash(algo, content.get_hash(algo))
                 for row in rows:
                     if getattr(row, algo) != content.get_hash(algo):
                         # collision of token(partition key), ignore this
                         # row
                         continue
 
                     for algo in HASH_ALGORITHMS:
                         if getattr(row, algo) != content.get_hash(algo):
                             # This hash didn't match; discard the row.
                             collisions.append(
                                 {algo: getattr(row, algo) for algo in HASH_ALGORITHMS}
                             )
 
                 if collisions:
                     collisions.append(content.hashes())
                     raise HashCollision(algo, content.get_hash(algo), collisions)
 
             (token, insertion_finalizer) = self._cql_runner.content_add_prepare(
                 ContentRow(**remove_keys(content.to_dict(), ("data",)))
             )
 
             # Then add to index tables
             for algo in HASH_ALGORITHMS:
                 self._cql_runner.content_index_add_one(algo, content, token)
 
             # Then to the main table
             insertion_finalizer()
 
         summary = {
             "content:add": content_add,
         }
 
         if with_data:
             summary["content:add:bytes"] = content_add_bytes
 
         return summary
 
     def content_add(self, content: List[Content]) -> Dict:
         contents = [attr.evolve(c, ctime=now()) for c in content]
         return self._content_add(list(contents), with_data=True)
 
     def content_update(
         self, contents: List[Dict[str, Any]], keys: List[str] = []
     ) -> None:
         raise NotImplementedError(
             "content_update is not supported by the Cassandra backend"
         )
 
     def content_add_metadata(self, content: List[Content]) -> Dict:
         return self._content_add(content, with_data=False)
 
     def content_get_data(self, content: Sha1) -> Optional[bytes]:
         # FIXME: Make this method support slicing the `data`
         return self.objstorage.content_get(content)
 
     def content_get_partition(
         self,
         partition_id: int,
         nb_partitions: int,
         page_token: Optional[str] = None,
         limit: int = 1000,
     ) -> PagedResult[Content]:
         if limit is None:
             raise StorageArgumentException("limit should not be None")
 
         # Compute start and end of the range of tokens covered by the
         # requested partition
         partition_size = (TOKEN_END - TOKEN_BEGIN) // nb_partitions
         range_start = TOKEN_BEGIN + partition_id * partition_size
         range_end = TOKEN_BEGIN + (partition_id + 1) * partition_size
 
         # offset the range start according to the `page_token`.
         if page_token is not None:
             if not (range_start <= int(page_token) <= range_end):
                 raise StorageArgumentException("Invalid page_token.")
             range_start = int(page_token)
 
         next_page_token: Optional[str] = None
 
         rows = self._cql_runner.content_get_token_range(
             range_start, range_end, limit + 1
         )
         contents = []
         for counter, (tok, row) in enumerate(rows):
             if row.status == "absent":
                 continue
             row_d = row.to_dict()
             if counter >= limit:
                 next_page_token = str(tok)
                 break
             contents.append(Content(**row_d))
 
         assert len(contents) <= limit
         return PagedResult(results=contents, next_page_token=next_page_token)
 
     def content_get(self, contents: List[Sha1]) -> List[Optional[Content]]:
         contents_by_sha1: Dict[Sha1, Optional[Content]] = {}
         for sha1 in contents:
             # Get all (sha1, sha1_git, sha256, blake2s256) whose sha1
             # matches the argument, from the index table ('content_by_sha1')
             for row in self._content_get_from_hash("sha1", sha1):
                 row_d = row.to_dict()
                 row_d.pop("ctime")
                 content = Content(**row_d)
                 contents_by_sha1[content.sha1] = content
         return [contents_by_sha1.get(sha1) for sha1 in contents]
 
     def content_find(self, content: Dict[str, Any]) -> List[Content]:
         # Find an algorithm that is common to all the requested contents.
         # It will be used to do an initial filtering efficiently.
         filter_algos = list(set(content).intersection(HASH_ALGORITHMS))
         if not filter_algos:
             raise StorageArgumentException(
                 "content keys must contain at least one "
                 f"of: {', '.join(sorted(HASH_ALGORITHMS))}"
             )
         common_algo = filter_algos[0]
 
         results = []
         rows = self._content_get_from_hash(common_algo, content[common_algo])
         for row in rows:
             # Re-check all the hashes, in case of collisions (either of the
             # hash of the partition key, or the hashes in it)
             for algo in HASH_ALGORITHMS:
                 if content.get(algo) and getattr(row, algo) != content[algo]:
                     # This hash didn't match; discard the row.
                     break
             else:
                 # All hashes match, keep this row.
                 row_d = row.to_dict()
                 row_d["ctime"] = row.ctime.replace(tzinfo=datetime.timezone.utc)
                 results.append(Content(**row_d))
         return results
 
     def content_missing(
         self, contents: List[Dict[str, Any]], key_hash: str = "sha1"
     ) -> Iterable[bytes]:
         if key_hash not in DEFAULT_ALGORITHMS:
             raise StorageArgumentException(
                 "key_hash should be one of {','.join(DEFAULT_ALGORITHMS)}"
             )
 
         for content in contents:
             res = self.content_find(content)
             if not res:
                 yield content[key_hash]
 
     def content_missing_per_sha1(self, contents: List[bytes]) -> Iterable[bytes]:
         return self.content_missing([{"sha1": c for c in contents}])
 
     def content_missing_per_sha1_git(
         self, contents: List[Sha1Git]
     ) -> Iterable[Sha1Git]:
         return self.content_missing(
             [{"sha1_git": c for c in contents}], key_hash="sha1_git"
         )
 
     def content_get_random(self) -> Sha1Git:
-        return self._cql_runner.content_get_random().sha1_git
+        content = self._cql_runner.content_get_random()
+        assert content, "Could not find any content"
+        return content.sha1_git
 
     def _skipped_content_add(self, contents: List[SkippedContent]) -> Dict:
         # Filter-out content already in the database.
         contents = [
             c
             for c in contents
             if not self._cql_runner.skipped_content_get_from_pk(c.to_dict())
         ]
 
         self.journal_writer.skipped_content_add(contents)
 
         for content in contents:
             # Compute token of the row in the main table
             (token, insertion_finalizer) = self._cql_runner.skipped_content_add_prepare(
                 SkippedContentRow.from_dict({"origin": None, **content.to_dict()})
             )
 
             # Then add to index tables
             for algo in HASH_ALGORITHMS:
                 self._cql_runner.skipped_content_index_add_one(algo, content, token)
 
             # Then to the main table
             insertion_finalizer()
 
         return {"skipped_content:add": len(contents)}
 
     def skipped_content_add(self, content: List[SkippedContent]) -> Dict:
         contents = [attr.evolve(c, ctime=now()) for c in content]
         return self._skipped_content_add(contents)
 
     def skipped_content_missing(
         self, contents: List[Dict[str, Any]]
     ) -> Iterable[Dict[str, Any]]:
         for content in contents:
             if not self._cql_runner.skipped_content_get_from_pk(content):
                 yield {algo: content[algo] for algo in DEFAULT_ALGORITHMS}
 
     def directory_add(self, directories: List[Directory]) -> Dict:
         # Filter out directories that are already inserted.
         missing = self.directory_missing([dir_.id for dir_ in directories])
         directories = [dir_ for dir_ in directories if dir_.id in missing]
 
         self.journal_writer.directory_add(directories)
 
         for directory in directories:
             # Add directory entries to the 'directory_entry' table
             for entry in directory.entries:
                 self._cql_runner.directory_entry_add_one(
                     DirectoryEntryRow(directory_id=directory.id, **entry.to_dict())
                 )
 
             # Add the directory *after* adding all the entries, so someone
             # calling snapshot_get_branch in the meantime won't end up
             # with half the entries.
             self._cql_runner.directory_add_one(DirectoryRow(id=directory.id))
 
         return {"directory:add": len(directories)}
 
     def directory_missing(self, directories: List[Sha1Git]) -> Iterable[Sha1Git]:
         return self._cql_runner.directory_missing(directories)
 
     def _join_dentry_to_content(self, dentry: DirectoryEntry) -> Dict[str, Any]:
         keys = (
             "status",
             "sha1",
             "sha1_git",
             "sha256",
             "length",
         )
         ret = dict.fromkeys(keys)
         ret.update(dentry.to_dict())
         if ret["type"] == "file":
             contents = self.content_find({"sha1_git": ret["target"]})
             if contents:
                 content = contents[0]
                 for key in keys:
                     ret[key] = getattr(content, key)
         return ret
 
     def _directory_ls(
         self, directory_id: Sha1Git, recursive: bool, prefix: bytes = b""
     ) -> Iterable[Dict[str, Any]]:
         if self.directory_missing([directory_id]):
             return
         rows = list(self._cql_runner.directory_entry_get([directory_id]))
 
         for row in rows:
             entry_d = row.to_dict()
             # Build and yield the directory entry dict
             del entry_d["directory_id"]
             entry = DirectoryEntry.from_dict(entry_d)
             ret = self._join_dentry_to_content(entry)
             ret["name"] = prefix + ret["name"]
             ret["dir_id"] = directory_id
             yield ret
 
             if recursive and ret["type"] == "dir":
                 yield from self._directory_ls(
                     ret["target"], True, prefix + ret["name"] + b"/"
                 )
 
     def directory_entry_get_by_path(
         self, directory: Sha1Git, paths: List[bytes]
     ) -> Optional[Dict[str, Any]]:
         return self._directory_entry_get_by_path(directory, paths, b"")
 
     def _directory_entry_get_by_path(
         self, directory: Sha1Git, paths: List[bytes], prefix: bytes
     ) -> Optional[Dict[str, Any]]:
         if not paths:
             return None
 
         contents = list(self.directory_ls(directory))
 
         if not contents:
             return None
 
         def _get_entry(entries, name):
             """Finds the entry with the requested name, prepends the
             prefix (to get its full path), and returns it.
 
             If no entry has that name, returns None."""
             for entry in entries:
                 if entry["name"] == name:
                     entry = entry.copy()
                     entry["name"] = prefix + entry["name"]
                     return entry
 
         first_item = _get_entry(contents, paths[0])
 
         if len(paths) == 1:
             return first_item
 
         if not first_item or first_item["type"] != "dir":
             return None
 
         return self._directory_entry_get_by_path(
             first_item["target"], paths[1:], prefix + paths[0] + b"/"
         )
 
     def directory_ls(
         self, directory: Sha1Git, recursive: bool = False
     ) -> Iterable[Dict[str, Any]]:
         yield from self._directory_ls(directory, recursive)
 
     def directory_get_random(self) -> Sha1Git:
-        return self._cql_runner.directory_get_random().id
+        directory = self._cql_runner.directory_get_random()
+        assert directory, "Could not find any directory"
+        return directory.id
 
     def revision_add(self, revisions: List[Revision]) -> Dict:
         # Filter-out revisions already in the database
         missing = self.revision_missing([rev.id for rev in revisions])
         revisions = [rev for rev in revisions if rev.id in missing]
         self.journal_writer.revision_add(revisions)
 
         for revision in revisions:
             revobject = converters.revision_to_db(revision)
             if revobject:
                 # Add parents first
                 for (rank, parent) in enumerate(revision.parents):
                     self._cql_runner.revision_parent_add_one(
                         RevisionParentRow(
                             id=revobject.id, parent_rank=rank, parent_id=parent
                         )
                     )
 
                 # Then write the main revision row.
                 # Writing this after all parents were written ensures that
                 # read endpoints don't return a partial view while writing
                 # the parents
                 self._cql_runner.revision_add_one(revobject)
 
         return {"revision:add": len(revisions)}
 
     def revision_missing(self, revisions: List[Sha1Git]) -> Iterable[Sha1Git]:
         return self._cql_runner.revision_missing(revisions)
 
     def revision_get(
         self, revisions: List[Sha1Git]
     ) -> Iterable[Optional[Dict[str, Any]]]:
         rows = self._cql_runner.revision_get(revisions)
         revs = {}
         for row in rows:
             # TODO: use a single query to get all parents?
             # (it might have lower latency, but requires more code and more
             # bandwidth, because revision id would be part of each returned
             # row)
             parents = tuple(self._cql_runner.revision_parent_get(row.id))
             # parent_rank is the clustering key, so results are already
             # sorted by rank.
             rev = converters.revision_from_db(row, parents=parents)
             revs[rev.id] = rev.to_dict()
 
         for rev_id in revisions:
             yield revs.get(rev_id)
 
     def _get_parent_revs(
         self,
         rev_ids: Iterable[Sha1Git],
         seen: Set[Sha1Git],
         limit: Optional[int],
         short: bool,
     ) -> Union[
         Iterable[Dict[str, Any]], Iterable[Tuple[Sha1Git, Tuple[Sha1Git, ...]]],
     ]:
         if limit and len(seen) >= limit:
             return
         rev_ids = [id_ for id_ in rev_ids if id_ not in seen]
         if not rev_ids:
             return
         seen |= set(rev_ids)
 
         # We need this query, even if short=True, to return consistent
         # results (ie. not return only a subset of a revision's parents
         # if it is being written)
         if short:
             ids = self._cql_runner.revision_get_ids(rev_ids)
             for id_ in ids:
                 # TODO: use a single query to get all parents?
                 # (it might have less latency, but requires less code and more
                 # bandwidth (because revision id would be part of each returned
                 # row)
                 parents = tuple(self._cql_runner.revision_parent_get(id_))
 
                 # parent_rank is the clustering key, so results are already
                 # sorted by rank.
 
                 yield (id_, parents)
                 yield from self._get_parent_revs(parents, seen, limit, short)
         else:
             rows = self._cql_runner.revision_get(rev_ids)
 
             for row in rows:
                 # TODO: use a single query to get all parents?
                 # (it might have less latency, but requires less code and more
                 # bandwidth (because revision id would be part of each returned
                 # row)
                 parents = tuple(self._cql_runner.revision_parent_get(row.id))
 
                 # parent_rank is the clustering key, so results are already
                 # sorted by rank.
 
                 rev = converters.revision_from_db(row, parents=parents)
                 yield rev.to_dict()
                 yield from self._get_parent_revs(parents, seen, limit, short)
 
     def revision_log(
         self, revisions: List[Sha1Git], limit: Optional[int] = None
     ) -> Iterable[Optional[Dict[str, Any]]]:
         seen: Set[Sha1Git] = set()
         yield from self._get_parent_revs(revisions, seen, limit, False)
 
     def revision_shortlog(
         self, revisions: List[Sha1Git], limit: Optional[int] = None
     ) -> Iterable[Optional[Tuple[Sha1Git, Tuple[Sha1Git, ...]]]]:
         seen: Set[Sha1Git] = set()
         yield from self._get_parent_revs(revisions, seen, limit, True)
 
     def revision_get_random(self) -> Sha1Git:
-        return self._cql_runner.revision_get_random().id
+        revision = self._cql_runner.revision_get_random()
+        assert revision, "Could not find any revision"
+        return revision.id
 
     def release_add(self, releases: List[Release]) -> Dict:
         to_add = []
         for rel in releases:
             if rel not in to_add:
                 to_add.append(rel)
         missing = set(self.release_missing([rel.id for rel in to_add]))
         to_add = [rel for rel in to_add if rel.id in missing]
 
         self.journal_writer.release_add(to_add)
 
         for release in to_add:
             if release:
                 self._cql_runner.release_add_one(converters.release_to_db(release))
 
         return {"release:add": len(to_add)}
 
     def release_missing(self, releases: List[Sha1Git]) -> Iterable[Sha1Git]:
         return self._cql_runner.release_missing(releases)
 
     def release_get(
         self, releases: List[Sha1Git]
     ) -> Iterable[Optional[Dict[str, Any]]]:
         rows = self._cql_runner.release_get(releases)
         rels = {}
         for row in rows:
             release = converters.release_from_db(row)
             rels[row.id] = release.to_dict()
 
         for rel_id in releases:
             yield rels.get(rel_id)
 
     def release_get_random(self) -> Sha1Git:
-        return self._cql_runner.release_get_random().id
+        release = self._cql_runner.release_get_random()
+        assert release, "Could not find any release"
+        return release.id
 
     def snapshot_add(self, snapshots: List[Snapshot]) -> Dict:
         missing = self._cql_runner.snapshot_missing([snp.id for snp in snapshots])
         snapshots = [snp for snp in snapshots if snp.id in missing]
 
         for snapshot in snapshots:
             self.journal_writer.snapshot_add([snapshot])
 
             # Add branches
             for (branch_name, branch) in snapshot.branches.items():
                 if branch is None:
                     target_type: Optional[str] = None
                     target: Optional[bytes] = None
                 else:
                     target_type = branch.target_type.value
                     target = branch.target
                 self._cql_runner.snapshot_branch_add_one(
                     SnapshotBranchRow(
                         snapshot_id=snapshot.id,
                         name=branch_name,
                         target_type=target_type,
                         target=target,
                     )
                 )
 
             # Add the snapshot *after* adding all the branches, so someone
             # calling snapshot_get_branch in the meantime won't end up
             # with half the branches.
             self._cql_runner.snapshot_add_one(SnapshotRow(id=snapshot.id))
 
         return {"snapshot:add": len(snapshots)}
 
     def snapshot_missing(self, snapshots: List[Sha1Git]) -> Iterable[Sha1Git]:
         return self._cql_runner.snapshot_missing(snapshots)
 
     def snapshot_get(self, snapshot_id: Sha1Git) -> Optional[Dict[str, Any]]:
         d = self.snapshot_get_branches(snapshot_id)
         if d is None:
             return None
         return {
             "id": d["id"],
             "branches": {
                 name: branch.to_dict() if branch else None
                 for (name, branch) in d["branches"].items()
             },
             "next_branch": d["next_branch"],
         }
 
     def snapshot_get_by_origin_visit(
         self, origin: str, visit: int
     ) -> Optional[Dict[str, Any]]:
         visit_status = self.origin_visit_status_get_latest(
             origin, visit, require_snapshot=True
         )
         if visit_status and visit_status.snapshot:
             return self.snapshot_get(visit_status.snapshot)
         return None
 
     def snapshot_count_branches(
         self, snapshot_id: Sha1Git
     ) -> Optional[Dict[Optional[str], int]]:
         if self._cql_runner.snapshot_missing([snapshot_id]):
             # Makes sure we don't fetch branches for a snapshot that is
             # being added.
             return None
         return self._cql_runner.snapshot_count_branches(snapshot_id)
 
     def snapshot_get_branches(
         self,
         snapshot_id: Sha1Git,
         branches_from: bytes = b"",
         branches_count: int = 1000,
         target_types: Optional[List[str]] = None,
     ) -> Optional[PartialBranches]:
         if self._cql_runner.snapshot_missing([snapshot_id]):
             # Makes sure we don't fetch branches for a snapshot that is
             # being added.
             return None
 
         branches: List = []
         while len(branches) < branches_count + 1:
             new_branches = list(
                 self._cql_runner.snapshot_branch_get(
                     snapshot_id, branches_from, branches_count + 1
                 )
             )
 
             if not new_branches:
                 break
 
             branches_from = new_branches[-1].name
 
             new_branches_filtered = new_branches
 
             # Filter by target_type
             if target_types:
                 new_branches_filtered = [
                     branch
                     for branch in new_branches_filtered
                     if branch.target is not None and branch.target_type in target_types
                 ]
 
             branches.extend(new_branches_filtered)
 
             if len(new_branches) < branches_count + 1:
                 break
 
         if len(branches) > branches_count:
             last_branch = branches.pop(-1).name
         else:
             last_branch = None
 
         return PartialBranches(
             id=snapshot_id,
             branches={
                 branch.name: None
                 if branch.target is None
                 else SnapshotBranch(
                     target=branch.target, target_type=TargetType(branch.target_type)
                 )
                 for branch in branches
             },
             next_branch=last_branch,
         )
 
     def snapshot_get_random(self) -> Sha1Git:
-        return self._cql_runner.snapshot_get_random().id
+        snapshot = self._cql_runner.snapshot_get_random()
+        assert snapshot, "Could not find any snapshot"
+        return snapshot.id
 
     def object_find_by_sha1_git(self, ids: List[Sha1Git]) -> Dict[Sha1Git, List[Dict]]:
         results: Dict[Sha1Git, List[Dict]] = {id_: [] for id_ in ids}
         missing_ids = set(ids)
 
         # Mind the order, revision is the most likely one for a given ID,
         # so we check revisions first.
-        queries = [
+        queries: List[Tuple[str, Callable[[List[Sha1Git]], List[Sha1Git]]]] = [
             ("revision", self._cql_runner.revision_missing),
             ("release", self._cql_runner.release_missing),
             ("content", self._cql_runner.content_missing_by_sha1_git),
             ("directory", self._cql_runner.directory_missing),
         ]
 
         for (object_type, query_fn) in queries:
-            found_ids = missing_ids - set(query_fn(missing_ids))
+            found_ids = missing_ids - set(query_fn(list(missing_ids)))
             for sha1_git in found_ids:
                 results[sha1_git].append(
                     {"sha1_git": sha1_git, "type": object_type,}
                 )
                 missing_ids.remove(sha1_git)
 
             if not missing_ids:
                 # We found everything, skipping the next queries.
                 break
 
         return results
 
     def origin_get(self, origins: List[str]) -> Iterable[Optional[Origin]]:
         return [self.origin_get_one(origin) for origin in origins]
 
     def origin_get_one(self, origin_url: str) -> Optional[Origin]:
         """Given an origin url, return the origin if it exists, None otherwise
 
         """
         rows = list(self._cql_runner.origin_get_by_url(origin_url))
         if rows:
             assert len(rows) == 1
             return Origin(url=rows[0].url)
         else:
             return None
 
     def origin_get_by_sha1(self, sha1s: List[bytes]) -> List[Optional[Dict[str, Any]]]:
         results = []
         for sha1 in sha1s:
             rows = list(self._cql_runner.origin_get_by_sha1(sha1))
             origin = {"url": rows[0].url} if rows else None
             results.append(origin)
         return results
 
     def origin_list(
         self, page_token: Optional[str] = None, limit: int = 100
     ) -> PagedResult[Origin]:
         # Compute what token to begin the listing from
         start_token = TOKEN_BEGIN
         if page_token:
             start_token = int(page_token)
             if not (TOKEN_BEGIN <= start_token <= TOKEN_END):
                 raise StorageArgumentException("Invalid page_token.")
         next_page_token = None
 
         origins = []
         # Take one more origin so we can reuse it as the next page token if any
         for (tok, row) in self._cql_runner.origin_list(start_token, limit + 1):
             origins.append(Origin(url=row.url))
             # keep reference of the last id for pagination purposes
             last_id = tok
 
         if len(origins) > limit:
             # last origin id is the next page token
             next_page_token = str(last_id)
             # excluding that origin from the result to respect the limit size
             origins = origins[:limit]
 
         assert len(origins) <= limit
 
         return PagedResult(results=origins, next_page_token=next_page_token)
 
     def origin_search(
         self,
         url_pattern: str,
         page_token: Optional[str] = None,
         limit: int = 50,
         regexp: bool = False,
         with_visit: bool = False,
     ) -> PagedResult[Origin]:
         # TODO: remove this endpoint, swh-search should be used instead.
         next_page_token = None
         offset = int(page_token) if page_token else 0
 
         origin_rows = [row for row in self._cql_runner.origin_iter_all()]
         if regexp:
             pat = re.compile(url_pattern)
             origin_rows = [row for row in origin_rows if pat.search(row.url)]
         else:
             origin_rows = [row for row in origin_rows if url_pattern in row.url]
 
         if with_visit:
             origin_rows = [row for row in origin_rows if row.next_visit_id > 1]
 
         origins = [Origin(url=row.url) for row in origin_rows]
 
         origins = origins[offset : offset + limit + 1]
         if len(origins) > limit:
             # next offset
             next_page_token = str(offset + limit)
             # excluding that origin from the result to respect the limit size
             origins = origins[:limit]
 
         assert len(origins) <= limit
         return PagedResult(results=origins, next_page_token=next_page_token)
 
     def origin_add(self, origins: List[Origin]) -> Dict[str, int]:
         to_add = [ori for ori in origins if self.origin_get_one(ori.url) is None]
         self.journal_writer.origin_add(to_add)
         for origin in to_add:
             self._cql_runner.origin_add_one(
                 OriginRow(sha1=hash_url(origin.url), url=origin.url, next_visit_id=1)
             )
         return {"origin:add": len(to_add)}
 
     def origin_visit_add(self, visits: List[OriginVisit]) -> Iterable[OriginVisit]:
         for visit in visits:
             origin = self.origin_get_one(visit.origin)
             if not origin:  # Cannot add a visit without an origin
                 raise StorageArgumentException("Unknown origin %s", visit.origin)
 
         all_visits = []
         nb_visits = 0
         for visit in visits:
             nb_visits += 1
             if not visit.visit:
                 visit_id = self._cql_runner.origin_generate_unique_visit_id(
                     visit.origin
                 )
                 visit = attr.evolve(visit, visit=visit_id)
             self.journal_writer.origin_visit_add([visit])
             self._cql_runner.origin_visit_add_one(OriginVisitRow(**visit.to_dict()))
             assert visit.visit is not None
             all_visits.append(visit)
             self._origin_visit_status_add(
                 OriginVisitStatus(
                     origin=visit.origin,
                     visit=visit.visit,
                     date=visit.date,
                     status="created",
                     snapshot=None,
                 )
             )
 
         return all_visits
 
     def _origin_visit_status_add(self, visit_status: OriginVisitStatus) -> None:
         """Add an origin visit status"""
         self.journal_writer.origin_visit_status_add([visit_status])
         self._cql_runner.origin_visit_status_add_one(
             converters.visit_status_to_row(visit_status)
         )
 
     def origin_visit_status_add(self, visit_statuses: List[OriginVisitStatus]) -> None:
         # First round to check existence (fail early if any is ko)
         for visit_status in visit_statuses:
             origin_url = self.origin_get_one(visit_status.origin)
             if not origin_url:
                 raise StorageArgumentException(f"Unknown origin {visit_status.origin}")
 
         for visit_status in visit_statuses:
             self._origin_visit_status_add(visit_status)
 
     def _origin_visit_apply_last_status(self, visit: Dict[str, Any]) -> Dict[str, Any]:
         """Retrieve the latest visit status information for the origin visit.
         Then merge it with the visit and return it.
 
         """
         row = self._cql_runner.origin_visit_status_get_latest(
             visit["origin"], visit["visit"]
         )
         assert row is not None
         visit_status = converters.row_to_visit_status(row)
         return {
             # default to the values in visit
             **visit,
             # override with the last update
             **visit_status.to_dict(),
             # visit['origin'] is the URL (via a join), while
             # visit_status['origin'] is only an id.
             "origin": visit["origin"],
             # but keep the date of the creation of the origin visit
             "date": visit["date"],
         }
 
     def _origin_visit_get_latest_status(self, visit: OriginVisit) -> OriginVisitStatus:
         """Retrieve the latest visit status information for the origin visit object.
 
         """
+        assert visit.visit
         row = self._cql_runner.origin_visit_status_get_latest(visit.origin, visit.visit)
         assert row is not None
         visit_status = converters.row_to_visit_status(row)
         return attr.evolve(visit_status, origin=visit.origin)
 
     @staticmethod
     def _format_origin_visit_row(visit):
         return {
             **visit.to_dict(),
             "origin": visit.origin,
             "date": visit.date.replace(tzinfo=datetime.timezone.utc),
         }
 
     def origin_visit_get(
         self,
         origin: str,
         page_token: Optional[str] = None,
         order: ListOrder = ListOrder.ASC,
         limit: int = 10,
     ) -> PagedResult[OriginVisit]:
         if not isinstance(order, ListOrder):
             raise StorageArgumentException("order must be a ListOrder value")
         if page_token and not isinstance(page_token, str):
             raise StorageArgumentException("page_token must be a string.")
 
         next_page_token = None
-        visit_from = page_token and int(page_token)
+        visit_from = None if page_token is None else int(page_token)
         visits: List[OriginVisit] = []
         extra_limit = limit + 1
 
         rows = self._cql_runner.origin_visit_get(origin, visit_from, extra_limit, order)
         for row in rows:
             visits.append(converters.row_to_visit(row))
 
         assert len(visits) <= extra_limit
         if len(visits) == extra_limit:
             visits = visits[:limit]
             next_page_token = str(visits[-1].visit)
 
         return PagedResult(results=visits, next_page_token=next_page_token)
 
     def origin_visit_status_get(
         self,
         origin: str,
         visit: int,
         page_token: Optional[str] = None,
         order: ListOrder = ListOrder.ASC,
         limit: int = 10,
     ) -> PagedResult[OriginVisitStatus]:
         next_page_token = None
         date_from = None
         if page_token is not None:
             date_from = datetime.datetime.fromisoformat(page_token)
 
         # Take one more visit status so we can reuse it as the next page token if any
         rows = self._cql_runner.origin_visit_status_get_range(
             origin, visit, date_from, limit + 1, order
         )
         visit_statuses = [converters.row_to_visit_status(row) for row in rows]
         if len(visit_statuses) > limit:
             # last visit status date is the next page token
             next_page_token = str(visit_statuses[-1].date)
             # excluding that visit status from the result to respect the limit size
             visit_statuses = visit_statuses[:limit]
 
         return PagedResult(results=visit_statuses, next_page_token=next_page_token)
 
     def origin_visit_find_by_date(
         self, origin: str, visit_date: datetime.datetime
     ) -> Optional[OriginVisit]:
         # Iterator over all the visits of the origin
         # This should be ok for now, as there aren't too many visits
         # per origin.
         rows = list(self._cql_runner.origin_visit_get_all(origin))
 
         def key(visit):
             dt = visit.date.replace(tzinfo=datetime.timezone.utc) - visit_date
             return (abs(dt), -visit.visit)
 
         if rows:
             return converters.row_to_visit(min(rows, key=key))
         return None
 
     def origin_visit_get_by(self, origin: str, visit: int) -> Optional[OriginVisit]:
         row = self._cql_runner.origin_visit_get_one(origin, visit)
         if row:
             return converters.row_to_visit(row)
         return None
 
     def origin_visit_get_latest(
         self,
         origin: str,
         type: Optional[str] = None,
         allowed_statuses: Optional[List[str]] = None,
         require_snapshot: bool = False,
     ) -> Optional[OriginVisit]:
         if allowed_statuses and not set(allowed_statuses).intersection(VISIT_STATUSES):
             raise StorageArgumentException(
                 f"Unknown allowed statuses {','.join(allowed_statuses)}, only "
                 f"{','.join(VISIT_STATUSES)} authorized"
             )
         # TODO: Do not fetch all visits
         rows = self._cql_runner.origin_visit_get_all(origin)
         latest_visit = None
         for row in rows:
             visit = self._format_origin_visit_row(row)
             updated_visit = self._origin_visit_apply_last_status(visit)
             if type is not None and updated_visit["type"] != type:
                 continue
             if allowed_statuses and updated_visit["status"] not in allowed_statuses:
                 continue
             if require_snapshot and updated_visit["snapshot"] is None:
                 continue
 
             # updated_visit is a candidate
             if latest_visit is not None:
                 if updated_visit["date"] < latest_visit["date"]:
                     continue
                 if updated_visit["visit"] < latest_visit["visit"]:
                     continue
 
             latest_visit = updated_visit
 
         if latest_visit is None:
             return None
         return OriginVisit(
             origin=latest_visit["origin"],
             visit=latest_visit["visit"],
             date=latest_visit["date"],
             type=latest_visit["type"],
         )
 
     def origin_visit_status_get_latest(
         self,
         origin_url: str,
         visit: int,
         allowed_statuses: Optional[List[str]] = None,
         require_snapshot: bool = False,
     ) -> Optional[OriginVisitStatus]:
         if allowed_statuses and not set(allowed_statuses).intersection(VISIT_STATUSES):
             raise StorageArgumentException(
                 f"Unknown allowed statuses {','.join(allowed_statuses)}, only "
                 f"{','.join(VISIT_STATUSES)} authorized"
             )
         rows = list(
             self._cql_runner.origin_visit_status_get(
                 origin_url, visit, allowed_statuses, require_snapshot
             )
         )
         # filtering is done python side as we cannot do it server side
         if allowed_statuses:
             rows = [row for row in rows if row.status in allowed_statuses]
         if require_snapshot:
             rows = [row for row in rows if row.snapshot is not None]
         if not rows:
             return None
         return converters.row_to_visit_status(rows[0])
 
     def origin_visit_status_get_random(
         self, type: str
     ) -> Optional[Tuple[OriginVisit, OriginVisitStatus]]:
         back_in_the_day = now() - datetime.timedelta(weeks=12)  # 3 months back
 
         # Random position to start iteration at
         start_token = random.randint(TOKEN_BEGIN, TOKEN_END)
 
         # Iterator over all visits, ordered by token(origins) then visit_id
         rows = self._cql_runner.origin_visit_iter(start_token)
         for row in rows:
             visit = converters.row_to_visit(row)
             visit_status = self._origin_visit_get_latest_status(visit)
             if visit.date > back_in_the_day and visit_status.status == "full":
                 return visit, visit_status
         return None
 
     def stat_counters(self):
         rows = self._cql_runner.stat_counters()
         keys = (
             "content",
             "directory",
             "origin",
             "origin_visit",
             "release",
             "revision",
             "skipped_content",
             "snapshot",
         )
         stats = {key: 0 for key in keys}
         stats.update({row.object_type: row.count for row in rows})
         return stats
 
     def refresh_stat_counters(self):
         pass
 
     def raw_extrinsic_metadata_add(self, metadata: List[RawExtrinsicMetadata]) -> None:
         self.journal_writer.raw_extrinsic_metadata_add(metadata)
         for metadata_entry in metadata:
             if not self._cql_runner.metadata_authority_get(
                 metadata_entry.authority.type.value, metadata_entry.authority.url
             ):
                 raise StorageArgumentException(
                     f"Unknown authority {metadata_entry.authority}"
                 )
             if not self._cql_runner.metadata_fetcher_get(
                 metadata_entry.fetcher.name, metadata_entry.fetcher.version
             ):
                 raise StorageArgumentException(
                     f"Unknown fetcher {metadata_entry.fetcher}"
                 )
 
             try:
                 row = RawExtrinsicMetadataRow(
                     type=metadata_entry.type.value,
                     id=str(metadata_entry.id),
                     authority_type=metadata_entry.authority.type.value,
                     authority_url=metadata_entry.authority.url,
                     discovery_date=metadata_entry.discovery_date,
                     fetcher_name=metadata_entry.fetcher.name,
                     fetcher_version=metadata_entry.fetcher.version,
                     format=metadata_entry.format,
                     metadata=metadata_entry.metadata,
                     origin=metadata_entry.origin,
                     visit=metadata_entry.visit,
                     snapshot=map_optional(str, metadata_entry.snapshot),
                     release=map_optional(str, metadata_entry.release),
                     revision=map_optional(str, metadata_entry.revision),
                     path=metadata_entry.path,
                     directory=map_optional(str, metadata_entry.directory),
                 )
                 self._cql_runner.raw_extrinsic_metadata_add(row)
             except TypeError as e:
                 raise StorageArgumentException(*e.args)
 
     def raw_extrinsic_metadata_get(
         self,
         type: MetadataTargetType,
         id: Union[str, SWHID],
         authority: MetadataAuthority,
         after: Optional[datetime.datetime] = None,
         page_token: Optional[bytes] = None,
         limit: int = 1000,
     ) -> PagedResult[RawExtrinsicMetadata]:
         if type == MetadataTargetType.ORIGIN:
             if isinstance(id, SWHID):
                 raise StorageArgumentException(
                     f"raw_extrinsic_metadata_get called with type='origin', "
                     f"but provided id is an SWHID: {id!r}"
                 )
         else:
             if not isinstance(id, SWHID):
                 raise StorageArgumentException(
                     f"raw_extrinsic_metadata_get called with type!='origin', "
                     f"but provided id is not an SWHID: {id!r}"
                 )
 
         if page_token is not None:
             (after_date, after_fetcher_name, after_fetcher_url) = msgpack_loads(
                 base64.b64decode(page_token)
             )
             if after and after_date < after:
                 raise StorageArgumentException(
                     "page_token is inconsistent with the value of 'after'."
                 )
             entries = self._cql_runner.raw_extrinsic_metadata_get_after_date_and_fetcher(  # noqa
                 str(id),
                 authority.type.value,
                 authority.url,
                 after_date,
                 after_fetcher_name,
                 after_fetcher_url,
             )
         elif after is not None:
             entries = self._cql_runner.raw_extrinsic_metadata_get_after_date(
                 str(id), authority.type.value, authority.url, after
             )
         else:
             entries = self._cql_runner.raw_extrinsic_metadata_get(
                 str(id), authority.type.value, authority.url
             )
 
         if limit:
             entries = itertools.islice(entries, 0, limit + 1)
 
         results = []
         for entry in entries:
             discovery_date = entry.discovery_date.replace(tzinfo=datetime.timezone.utc)
 
             assert str(id) == entry.id
 
             result = RawExtrinsicMetadata(
                 type=MetadataTargetType(entry.type),
                 id=id,
                 authority=MetadataAuthority(
                     type=MetadataAuthorityType(entry.authority_type),
                     url=entry.authority_url,
                 ),
                 fetcher=MetadataFetcher(
                     name=entry.fetcher_name, version=entry.fetcher_version,
                 ),
                 discovery_date=discovery_date,
                 format=entry.format,
                 metadata=entry.metadata,
                 origin=entry.origin,
                 visit=entry.visit,
                 snapshot=map_optional(parse_swhid, entry.snapshot),
                 release=map_optional(parse_swhid, entry.release),
                 revision=map_optional(parse_swhid, entry.revision),
                 path=entry.path,
                 directory=map_optional(parse_swhid, entry.directory),
             )
 
             results.append(result)
 
         if len(results) > limit:
             results.pop()
             assert len(results) == limit
             last_result = results[-1]
             next_page_token: Optional[str] = base64.b64encode(
                 msgpack_dumps(
                     (
                         last_result.discovery_date,
                         last_result.fetcher.name,
                         last_result.fetcher.version,
                     )
                 )
             ).decode()
         else:
             next_page_token = None
 
         return PagedResult(next_page_token=next_page_token, results=results,)
 
     def metadata_fetcher_add(self, fetchers: List[MetadataFetcher]) -> None:
         self.journal_writer.metadata_fetcher_add(fetchers)
         for fetcher in fetchers:
             self._cql_runner.metadata_fetcher_add(
                 MetadataFetcherRow(
                     name=fetcher.name,
                     version=fetcher.version,
                     metadata=json.dumps(map_optional(dict, fetcher.metadata)),
                 )
             )
 
     def metadata_fetcher_get(
         self, name: str, version: str
     ) -> Optional[MetadataFetcher]:
         fetcher = self._cql_runner.metadata_fetcher_get(name, version)
         if fetcher:
             return MetadataFetcher(
                 name=fetcher.name,
                 version=fetcher.version,
                 metadata=json.loads(fetcher.metadata),
             )
         else:
             return None
 
     def metadata_authority_add(self, authorities: List[MetadataAuthority]) -> None:
         self.journal_writer.metadata_authority_add(authorities)
         for authority in authorities:
             self._cql_runner.metadata_authority_add(
                 MetadataAuthorityRow(
                     url=authority.url,
                     type=authority.type.value,
                     metadata=json.dumps(map_optional(dict, authority.metadata)),
                 )
             )
 
     def metadata_authority_get(
         self, type: MetadataAuthorityType, url: str
     ) -> Optional[MetadataAuthority]:
         authority = self._cql_runner.metadata_authority_get(type.value, url)
         if authority:
             return MetadataAuthority(
                 type=MetadataAuthorityType(authority.type),
                 url=authority.url,
                 metadata=json.loads(authority.metadata),
             )
         else:
             return None
 
     def clear_buffers(self, object_types: Optional[List[str]] = None) -> None:
         """Do nothing
 
         """
         return None
 
     def flush(self, object_types: Optional[List[str]] = None) -> Dict:
         return {}