This was seen by a user (Howard Wang#8417 Discord) in v1.3.2 when applying metadata:

2020-10-20 18:31:42 UTC:172.17.5.63(54744):t5br6hpuBHCetN33jJczdXRvTwfFXjBpANW5@hasura:[4585]:
DETAIL: Process 4585 waits for AccessExclusiveLock on relation 17646 of database 16396; blocked by process 458.

Process 458 waits for AccessShareLock on relation 17824 of database 16396; blocked by process 4585.

Process 4585: DROP FUNCTION IF EXISTS hdb_views."notify_hasura_channel_post_created_INSERT"() CASCADE

Process 458: SELECT "_subs"."result_id" , "_fld_resp"."root" AS "result" FROM UNNEST(($1)::uuid[], ($2)::json[]) AS...

This is causing hasura metadata apply command to fail and hence rollback of the desired upgrade.