SELECT blocks UPDATE

Hello,

if I am reading the documentation on explicit locking correctly, SELECT should never conflict with UPDATE. However, what I am observing as a result of this monitoring query:

SELECT bl.pid AS blocked_pid,

    a.usename              AS blocked_user,

    ka.query               AS blocking_statement,

    now() - ka.query_start AS blocking_duration,

    kl.pid                 AS blocking_pid,

    ka.usename             AS blocking_user,

    a.query                AS blocked_statement,

    now() - a.query_start  AS blocked_duration

FROM pg_catalog.pg_locks bl

JOIN pg_catalog.pg_stat_activity a ON a.pid = bl.pid

JOIN pg_catalog.pg_locks kl ON kl.transactionid = bl.transactionid AND kl.pid != bl.pid

JOIN pg_catalog.pg_stat_activity ka ON ka.pid = kl.pid

WHERE NOT bl.granted;

is this

Blocking statement: SELECT tmtranslat0_.id as id164_0_, tmtranslat1_.id as id101_1_, tmlanguage2_.id as id73_2_, ... FROM "TRANSLATION" ...

Blocked statement: UPDATE "TRANSLATION" SET fk_assignment_queue_item = 1000211 WHERE id IN (47032216)

I don't remember ever having problems with things like this. I am not even issuing SQL queries in parallel from my application (the execution is single-threaded). Now my application is stuck on the UPDATE statement.

1) How is it possible that these two statements block?
2) What can I do about it?

Thank you.

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