<para>

The <structfield>pid</structfield> column can be joined to the

<structfield>pid</structfield> column of the

<structname>pg_stat_activity</structname> view to get more

information on the session holding or waiting to hold each lock.

<structfield>pid</structfield> column of the <link

linkend="pg-stat-activity-view"><structname>pg_stat_activity</structname></link>

view to get more

information on the session holding or waiting to hold each lock,

for example

<programlisting>

SELECT * FROM pg_locks pl LEFT JOIN pg_stat_activity psa

ON pl.pid = psa.pid;

</programlisting>

Also, if you are using prepared transactions, the

<structfield>transaction</> column can be joined to the

<structfield>transaction</structfield> column of the

<structname>pg_prepared_xacts</structname> view to get more

information on prepared transactions that hold locks.

<structfield>virtualtransaction</> column can be joined to the

<structfield>transaction</structfield> column of the <link

linkend="view-pg-prepared-xacts"><structname>pg_prepared_xacts</structname></link>

view to get moreinformation on prepared transactions that hold locks.

(A prepared transaction can never be waiting for a lock,

but it continues to hold the locks it acquired while running.)

For example:

<programlisting>

SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx

ON pl.virtualtransaction = '-1/' || ppx.transaction;

</programlisting>

</para>

<para>