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Josh Berkus
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Added query and shell script to log transaction locks.
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‎README.md‎

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@@ -26,6 +26,21 @@ table_bloat_check.sql
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An overhauled table bloat check. Lists tables which are likely to be bloated and estimates bloat amounts. Requires PostgreSQL >= 8.4, superuser access, and a 64-bit compile.
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Locks
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=====
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Tools and a set of queries to analyze lock-blocking.
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transaction_locks.sql
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---------------------
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Requires: Postgres 9.2+
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Lists waiting transaction locks and what they're waiting on, if possible.
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Includes relation and query information, but realistically needs to be
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accompanied by full query logging to be useful. Needs to be run
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per active database.
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Additional Contributors
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=======================
@@ -34,4 +49,5 @@ In addition to the staff of PostgreSQL Experts, we are indebted
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to:
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* The authors of the check_postgres.pl script for supplying the
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original bloat queries on which our bloat queries are based.
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original bloat queries on which our bloat queries are based.
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* Andrew Gierth for help on various system queries.

‎locks/log_transaction_locks.sh‎

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#!/bin/bash
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# simple script to log transaction locks to a table
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# assumes that you're running it as the postgres user and don't need a password
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# change to path of psql
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PSQL='/usr/lib/postgresql/9.3/bin/psql'
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# change to database you're targeting
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DBNAME='somedb'
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# modify if required
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DBPORT='-p 5432'
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DBHOST='-h 127.0.0.1'
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$PSQL -c "INSERT INTO log_transaction_locks SELECT * FROM log_transaction_locks_view" -U postgres $DBNAME $DBPORT $DBHOST
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exit 0

‎locks/transaction_locks.sql‎

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-- query to analyze waiting transaction locks
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-- requires Postgres 9.2 or greater
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WITH table_locks AS (
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select pid,
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relation::regclass as lockobj,
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case when page is not null and tuple is not null then
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mode || ' on ' || page::text || ':' || tuple::text
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else
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mode
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end as lock_mode,
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locktype
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from pg_locks
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join pg_database
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ON pg_locks.database = pg_database.oid
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where relation is not null
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and pg_database.datname = current_database()
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order by lockobj
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),
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locked_list AS (
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select pid,
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array_agg(lockobj) as lock_relations,
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array_agg(lock_mode) as lock_modes,
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array_agg(locktype) as lock_types
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from table_locks
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group by pid
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),
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txn_locks AS (
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select pid, transactionid::text as lxid, granted
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from pg_locks
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where locktype = 'transactionid'
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union all
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select pid, virtualxid::text as lxid, granted
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from pg_locks
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where locktype = 'virtualxid'
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),
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txn_granted AS (
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select pid, lxid from txn_locks
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where granted
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),
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txn_waiting AS (
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select pid, lxid from txn_locks
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where not granted
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)
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select now() as lock_ts,
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txn_waiting.pid as waiting_pid,
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txn_waiting.lxid as wait_xid,
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txn_granted.pid as locked_pid,
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waiting_proc.application_name as waiting_app,
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waiting_proc.client_addr as waiting_addr,
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waiting_proc.xact_start as waiting_xact_start,
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waiting_proc.query_start as waiting_query_start,
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waiting_proc.state_change as waiting_start,
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waiting_proc.query as waiting_query,
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locked_proc.application_name as locked_app,
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locked_proc.client_addr as locked_addr,
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locked_proc.xact_start as locked_xact_start,
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locked_proc.query_start as locked_query_start,
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locked_proc.state as locked_state,
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locked_proc.state_change as locked_state_start,
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locked_proc.query as locked_last_query,
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waiting_locks.lock_relations as waiting_relations,
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waiting_locks.lock_modes as waiting_modes,
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waiting_locks.lock_types as waiting_lock_types,
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locked_locks.lock_relations as locked_relations,
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locked_locks.lock_modes as locked_modes,
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locked_locks.lock_types as locked_lock_types
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from txn_waiting
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JOIN pg_stat_activity as waiting_proc
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ON txn_waiting.pid = waiting_proc.pid
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LEFT OUTER JOIN txn_granted
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ON txn_waiting.lxid = txn_granted.lxid
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LEFT OUTER JOIN pg_stat_activity as locked_proc
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ON txn_granted.pid = locked_proc.pid
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LEFT OUTER JOIN locked_list AS waiting_locks
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ON txn_waiting.pid = waiting_locks.pid
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LEFT OUTER JOIN locked_list AS locked_locks
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ON txn_granted.pid = locked_locks.pid
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order by waiting_pid;
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‎locks/transaction_locks_setup.sql‎

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-- do statement to set things up for transaction lock logging
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-- written so that it can be run repeatedly
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DO $f$
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BEGIN
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PERFORM 1
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FROM pg_stat_user_tables
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WHERE relname = 'log_transaction_locks';
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IF NOT FOUND THEN
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CREATE VIEW log_transaction_locks_view
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AS
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WITH table_locks AS (
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select pid,
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relation::regclass as lockobj,
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case when page is not null and tuple is not null then
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mode || ' on ' || page::text || ':' || tuple::text
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else
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mode
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end as lock_mode,
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locktype
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from pg_locks
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join pg_database
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ON pg_locks.database = pg_database.oid
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where relation is not null
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and pg_database.datname = current_database()
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order by lockobj
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),
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locked_list AS (
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select pid,
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array_agg(lockobj) as lock_relations,
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array_agg(lock_mode) as lock_modes,
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array_agg(locktype) as lock_types
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from table_locks
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group by pid
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),
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txn_locks AS (
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select pid, transactionid::text as lxid, granted
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from pg_locks
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where locktype = 'transactionid'
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union all
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select pid, virtualxid::text as lxid, granted
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from pg_locks
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where locktype = 'virtualxid'
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),
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txn_granted AS (
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select pid, lxid from txn_locks
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where granted
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),
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txn_waiting AS (
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select pid, lxid from txn_locks
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where not granted
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)
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select now() as lock_ts,
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txn_waiting.pid as waiting_pid,
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txn_waiting.lxid as wait_xid,
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txn_granted.pid as locked_pid,
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waiting_proc.application_name as waiting_app,
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waiting_proc.client_addr as waiting_addr,
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waiting_proc.xact_start as waiting_xact_start,
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waiting_proc.query_start as waiting_query_start,
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waiting_proc.state_change as waiting_start,
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waiting_proc.query as waiting_query,
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locked_proc.application_name as locked_app,
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locked_proc.client_addr as locked_addr,
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locked_proc.xact_start as locked_xact_start,
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locked_proc.query_start as locked_query_start,
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locked_proc.state as locked_state,
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locked_proc.state_change as locked_state_start,
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locked_proc.query as locked_last_query,
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waiting_locks.lock_relations as waiting_relations,
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waiting_locks.lock_modes as waiting_modes,
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waiting_locks.lock_types as waiting_lock_types,
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locked_locks.lock_relations as locked_relations,
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locked_locks.lock_modes as locked_modes,
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locked_locks.lock_types as locked_lock_types
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from txn_waiting
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JOIN pg_stat_activity as waiting_proc
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ON txn_waiting.pid = waiting_proc.pid
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LEFT OUTER JOIN txn_granted
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ON txn_waiting.lxid = txn_granted.lxid
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LEFT OUTER JOIN pg_stat_activity as locked_proc
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ON txn_granted.pid = locked_proc.pid
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LEFT OUTER JOIN locked_list AS waiting_locks
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ON txn_waiting.pid = waiting_locks.pid
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LEFT OUTER JOIN locked_list AS locked_locks
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ON txn_granted.pid = locked_locks.pid
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order by waiting_pid;
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CREATE TABLE log_transaction_locks AS
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SELECT * FROM log_transaction_locks_view
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WHERE FALSE;
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END IF;
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END;
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$f$;

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