MemPalace/mempalace · error · BackendError

pgvector client has been closed

Error message

pgvector client has been closed

What it means

Error "pgvector client has been closed" thrown in MemPalace/mempalace.

Source

Thrown at mempalace/backends/pgvector.py:526

    def _connect(self):
        try:
            import psycopg
        except ImportError as exc:  # pragma: no cover - exercised only without the extra
            raise BackendError(
                "pgvector backend requires the optional 'psycopg' dependency; "
                "install mempalace[pgvector]"
            ) from exc
        # One client is shared across threads (PgVectorBackend caches a
        # single instance per config), so the read-create-store on self._conn
        # must hold the same lock _execute serializes on; unlocked, two
        # first-connect threads each opened a connection and the loser leaked
        # unclosed. The RLock makes the _execute -> _connect nesting safe. A
        # stalled connect blocks peers under the lock the same way any
        # in-flight query on this single shared connection already does.
        with self._lock:
            if self._closed:
                raise BackendError("pgvector client has been closed")
            if self._conn is not None and not getattr(self._conn, "closed", False):
                return self._conn
            try:
                self._conn = psycopg.connect(self._config.dsn)
            except Exception as exc:  # noqa: BLE001 - surface any driver failure uniformly
                raise BackendError(f"pgvector connection failed: {exc}") from exc
            return self._conn

    def _execute(self, sql: str, params=None, *, fetch: bool = False, many: bool = False):
        with self._lock:
            conn = self._connect()
            try:
                with conn.cursor() as cur:
                    if many:
                        cur.executemany(sql, params or [])
                        rows = None
                    else:
                        cur.execute(sql, params or [])

View on GitHub (pinned to 06cb6987f0)

Solutions

1. Do not use the client after close(); create a new pgvector client/connection

When it happens

Trigger: Thrown at mempalace/backends/pgvector.py:526 when the library encounters an invalid state.

Common situations: Client was closed (explicitly or via context manager) and then reused.

AI-assisted analysis of MemPalace/mempalace@06cb6987f0 (2026-08-15). Data as JSON: /api/errors/dd89a63822b36876. Report an issue: GitHub.