redis/redis-py · error · ConnectionError

Invalid Database

Error message

Invalid Database

What it means

Raised in on_connect (connection.py:1237-1240) when db is set and the SELECT reply is not 'OK'. After authenticating, the library issues SELECT <db> to move to the configured logical database; a non-OK reply means the database index is invalid or unavailable, so the connection is aborted rather than silently running on db 0.

Solutions

1. Use a db index within [0, databases-1] (default 0-15).
2. Check CONFIG GET databases on the server and lower your db index accordingly.
3. Omit db to default to 0.
4. Prefer separate Redis instances/key prefixes over high db indexes.

Example fix

# before
r = redis.Redis(host=h, port=p, db=20)
# after
r = redis.Redis(host=h, port=p, db=10)  # within 0-15

def resolve_db(raw, max_dbs=16):
    db = int(raw)
    if not (0 <= db < max_dbs):
        raise ValueError(f'db must be in [0,{max_dbs-1}], got {db}')
    return db

# optionally read the server limit:
maxdbs = redis.Redis(host=h, port=p).config_get('databases').get('databases', 16)
r = redis.Redis(host=h, port=p, db=resolve_db(raw_db, int(maxdbs)))

def is_valid_db(v, max_dbs=16) -> bool:
    try:
        return 0 <= int(v) < max_dbs
    except (TypeError, ValueError):
        return False

from redis.exceptions import ConnectionError
try:
    r = redis.Redis(host=h, port=p, db=db_index)
    r.ping()
except ConnectionError as e:
    if 'Invalid Database' in str(e):
        r = redis.Redis(host=h, port=p, db=0)  # safe default
    else:
        raise

When it happens

Trigger: Passing db=16 (or any index >= the configured number of databases) — default Redis ships 16 databases (0-15); passing a negative db; a server configured with fewer databases than the requested index.

Common situations: Migrating from another system with more logical DBs; typo in db index; reducing 'databases' in redis.conf without updating clients.

Related errors

• Error setting client name
• Cache must implement CacheInterface
• Cannot enable maintenance notifications for connection…
• Invalid SSL Certificate Requirements Flag
• Invalid ssl verify flag

AI-assisted analysis of redis/redis-py@6a6b581b48 (2026-08-10). Data as JSON: /api/errors/09a15ae9d7c80ae6. Report an issue: GitHub.

Appendix: source

Thrown at redis/connection.py:1240

        try:
            if self.driver_info and self.driver_info.lib_version:
                self.send_command(
                    "CLIENT",
                    "SETINFO",
                    "LIB-VER",
                    self.driver_info.lib_version,
                    check_health=check_health,
                )
                self.read_response()
        except ResponseError:
            pass

        # if a database is specified, switch to it
        if self.db:
            self.send_command("SELECT", self.db, check_health=check_health)
            if str_if_bytes(self.read_response()) != "OK":
                raise ConnectionError("Invalid Database")

    def disconnect(self, *args, **kwargs):
        "Disconnects from the Redis server"
        # The server session is gone, so any HIMPORT fieldsets prepared on this
        # socket no longer exist; reset the tracking.
        self._reset_himport_state()
        self._parser.on_disconnect()

        conn_sock = self._sock
        self._sock = None
        # reset the reconnect flag
        self.reset_should_reconnect()

        if conn_sock is None:
            return

        if os.getpid() == self.pid:
            try:

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