---
title: "pgrowlocks — show a table's row locking information"
id: pgrowlocks
pg_version: "20devel"
---

<a id="pgrowlocks"></a>

## F.32. pgrowlocks — show a table's row locking information

The `pgrowlocks` module provides a function to show row locking information for a specified table. 

By default use is restricted to superusers, roles with privileges of the `pg_stat_scan_tables` role, and users with `SELECT` permissions on the table. 

<a id="pgrowlocks-overview"></a>

### F.32.1. Overview

```
pgrowlocks(text) returns setof record
```

The parameter is the name of a table. The result is a set of records, with one row for each locked row within the table. The output columns are shown in [Table F.22](pgrowlocks.md#pgrowlocks-columns). 

<a id="pgrowlocks-columns"></a>

**pgrowlocks Output Columns**

| Name | Type | Description | 
| --- | --- | --- |
| `locked_row` | `tid` | Tuple ID (TID) of locked row | 
| `locker` | `xid` | Transaction ID of locker, or multixact ID if multitransaction; see [Section 67.1](transaction-id.md) | 
| `multi` | `boolean` | True if locker is a multitransaction | 
| `xids` | `xid[]` | Transaction IDs of lockers (more than one if multitransaction) | 
| `modes` | `text[]` | Lock mode of lockers (more than one if multitransaction), an array of `For Key Share`, `For Share`, `For No Key Update`, `No Key Update`, `For Update`, `Update`. | 
| `pids` | `integer[]` | Process IDs of locking backends (more than one if multitransaction) | 

`pgrowlocks` takes `AccessShareLock` for the target table and reads each row one by one to collect the row locking information. This is not very speedy for a large table. Note that: 


1.  If an `ACCESS EXCLUSIVE` lock is taken on the table, `pgrowlocks` will be blocked. 
2.  `pgrowlocks` is not guaranteed to produce a self-consistent snapshot. It is possible that a new row lock is taken, or an old lock is freed, during its execution. 

`pgrowlocks` does not show the contents of locked rows. If you want to take a look at the row contents at the same time, you could do something like this: 
SELECT * FROM accounts AS a, pgrowlocks('accounts') AS p
  WHERE p.locked_row = a.ctid;
 Be aware however that such a query will be very inefficient. 

<a id="pgrowlocks-sample-output"></a>

### F.32.2. Sample Output


=# SELECT * FROM pgrowlocks('t1');
 locked_row | locker | multi | xids  |     modes      |  pids
------------+--------+-------+-------+----------------+--------
 (0,1)      |    609 | f     | {609} | {"For Share"}  | {3161}
 (0,2)      |    609 | f     | {609} | {"For Share"}  | {3161}
 (0,3)      |    607 | f     | {607} | {"For Update"} | {3107}
 (0,4)      |    607 | f     | {607} | {"For Update"} | {3107}
(4 rows)
<a id="pgrowlocks-author"></a>

### F.32.3. Author

Tatsuo Ishii