Lock table on postgresql 9.6

Question

i'm new in postgres administration and when developper run LOCK TABLE tab1; with PREPAREDstatement , postgres use ACCES EXCLUSIVE BY DEFAULT. My probelem is that the lock in table is still here after one week in view pg_prepared_xact and pg_locks even after restart of postgres and in pg_lock is like:

 vXID                 mode
-1/192836             AccessExclusiveLock

Name               DATABASE                  Owner             XID          prepared at
                   db1                       postgres          192836       20-07-2021

I would know why the LOCK is still here?? and how to solve it? and what is mean -1 in vXID?? because i can't even show my data on tab1

Answer 1

with PREPARED statement

Prepared transactions and prepared statements are very different things. What you have here is a prepared transaction. Surviving a restart is what prepared transactions are for. You need to find its "gid" in pg_prepared_xacts and then either manually commit it or roll it back. If you are not intentionally using prepared transactions, the you should set max_prepared_transactions =0, so this can't recur. If you are intentionally using them, you need to learn how to handle them.