suspend fun queryFlow(query: String, params: List<Any>, fetchSize: Int = 100) : Flow<T> {
        // use channelFlow for thread safety
        return channelFlow {
            val producer = this
            connection.inTransaction {c ->
                val cursorId = "cursor_${Random.nextULong()}"
                try {
                    c.sendPreparedStatement(
                        """
                            DECLARE $cursorId CURSOR FOR 
                            $query
                        """.trimIndent(), params
                    )

                    var resp: QueryResult? = null
                    while (resp == null || resp.rows.isNotEmpty()) {
                        resp = c.sendQuery("FETCH $fetchSize FROM $cursorId;")
                        resp.rows.forEach { row ->
                            val doc = json.decodeFromString(serializationStrategy,row.getString("json")?: error("empty json"))
                            producer.send(doc)
                        }
                    }

                } finally {
                    c.sendQuery("CLOSE $cursorId;")
                }
            }
        }
    }