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| title: pg_listener |
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| The `pg_listener` system catalog table supports the `LISTEN` and `NOTIFY` commands. A listener creates an entry in `pg_listener` for each notification name it is listening for. A notifier scans and updates each matching entry to show that a notification has occurred. The notifier also sends a signal (using the PID recorded in the table) to awaken the listener from sleep. |
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| This table is not currently used in HAWQ. |
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| <a id="topic1__gu143898"></a> |
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| | column | type | references | description | |
| |----------------|---------|------------|----------------------------------------------------------------------------------------------------------------------------------| |
| | `relname` | name | | Notify condition name. (The name need not match any actual relation in the database. | |
| | `listenerpid` | integer | | PID of the server process that created this entry. | |
| | `notification` | integer | | Zero if no event is pending for this listener. If an event is pending, the PID of the server process that sent the notification. | |
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| : <span class="tablecap">Table 1. pg\_catalog.pg\_listener</span> |
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