postgresql.py 文件源码

def _perform_vlob_update(self, intent):
        async with self.connection.acquire() as conn:
            async with conn.cursor() as cur:
                await cur.execute("SELECT version, read_trust_seed, write_trust_seed FROM "
                                  "vlobs WHERE id=%s ORDER BY version DESC;", (intent.id, ))
                ret = await cur.fetchone()
                if ret is None:
                    raise VlobNotFound('Vlob not found.')
                last_version, rts, wts = ret
                if wts != intent.trust_seed:
                    raise TrustSeedError('Invalid write trust seed.')
                if intent.version != last_version + 1:
                    raise VlobNotFound('Wrong blob version.')
                # TODO: insertion doesn't do atomic check of version
                await cur.execute("INSERT INTO vlobs VALUES (%s, %s, %s, %s, %s);",
                    (intent.id, intent.version, rts, wts, intent.blob))
                await cur.execute("NOTIFY vlob_updated, %s", (intent.id, ))