Contents
Functions
Sending Messages
send
Send a single message to a queue.
pgmq.send(
queue_name text,
msg jsonb,
delay integer DEFAULT 0
)
RETURNS SETOF bigint
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | msg | jsonb | The message to send to the queue | | delay | integer | Time in seconds before the message becomes visible. Defaults to 0. |
Example:
select * from pgmq.send('my_queue', '{"hello": "world"}');
send
------
4
send_batch
Send 1 or more messages to a queue.
pgmq.send_batch(
queue_name text,
msgs jsonb[],
delay integer DEFAULT 0
)
RETURNS SETOF bigint
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | msgs | jsonb[] | Array of messages to send to the queue | | delay | integer | Time in seconds before the messages becomes visible. Defaults to 0. |
select * from pgmq.send_batch('my_queue', ARRAY[
'{"hello": "world_0"}'::jsonb,
'{"hello": "world_1"}'::jsonb]
);
send_batch
------------
1
2
Reading Messages
read
Read 1 or more messages from a queue. The VT specifies the amount of time in seconds that the message will be invisible to other consumers after reading.
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | vt | integer | Time in seconds that the message become invisible after reading | | qty | integer | The number of messages to read from the queue. Defaults to 1 |
Example:
select * from pgmq.read('my_queue', 10, 2);
msg_id | read_ct | enqueued_at | vt | message
--------+---------+-------------------------------+-------------------------------+----------------------
1 | 1 | 2023-10-28 19:14:47.356595-05 | 2023-10-28 19:17:08.608922-05 | {"hello": "world_0"}
2 | 1 | 2023-10-28 19:14:47.356595-05 | 2023-10-28 19:17:08.608974-05 | {"hello": "world_1"}
(2 rows)
read_with_poll
Same as read(). Also provides convenient long-poll functionality.
When there are no messages in the queue, the function call will wait for max_poll_seconds in duration before returning.
If messages reach the queue during that duration, they will be read and returned immediately.
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | vt | integer | Time in seconds that the message become invisible after reading. | | qty | integer | The number of messages to read from the queue. Defaults to 1. | | max_poll_seconds | integer | Time in seconds to wait for new messages to reach the queue. Defaults to 5. | | poll_interval_ms | integer | Milliseconds between the internal poll operations. Defaults to 100. |
Example:
select * from pgmq.read_with_poll('my_queue', 1, 1, 5, 100);
msg_id | read_ct | enqueued_at | vt | message
--------+---------+-------------------------------+-------------------------------+--------------------
1 | 1 | 2023-10-28 19:09:09.177756-05 | 2023-10-28 19:27:00.337929-05 | {"hello": "world"}
pop
Reads a single message from a queue and deletes it upon read.
Note: utilization of pop() results in at-most-once delivery semantics if the consuming application does not guarantee processing of the message.
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue |
Example:
pgmq=# select * from pgmq.pop('my_queue');
msg_id | read_ct | enqueued_at | vt | message
--------+---------+-------------------------------+-------------------------------+--------------------
1 | 2 | 2023-10-28 19:09:09.177756-05 | 2023-10-28 19:27:00.337929-05 | {"hello": "world"}
Deleting/Archiving Messages
delete (single)
Deletes a single message from a queue.
pgmq.delete (queue_name text, msg_id: bigint)
RETURNS boolean
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | msg_id | bigint | Message ID of the message to delete |
Example:
select pgmq.delete('my_queue', 5);
delete
--------
t
delete (batch)
Delete one or many messages from a queue.
pgmq.delete (queue_name text, msg_ids: bigint[])
RETURNS SETOF bigint
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | msg_ids | bigint[] | Array of message IDs to delete |
Examples:
Delete two messages that exist.
select * from pgmq.delete('my_queue', ARRAY[2, 3]);
delete
--------
2
3
Delete two messages, one that exists and one that does not. Message 999 does not exist.
select * from pgmq.delete('my_queue', ARRAY[6, 999]);
delete
--------
6
purge_queue
Permanently deletes all messages in a queue. Returns the number of messages that were deleted.
purge_queue(queue_name text)
RETURN bigint
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue |
Example:
Purge the queue when it contains 8 messages;
select * from pgmq.purge_queue('my_queue');
purge_queue
-------------
8
archive (single)
Removes a single requested message from the specified queue and inserts it into the queue’s archive.
pgmq.archive(queue_name text, msg_id bigint)
RETURNS boolean
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | msg_id | bigint | Message ID of the message to archive |
Returns Boolean value indicating success or failure of the operation.
Example; remove message with ID 1 from queue my_queue and archive it:
SELECT * FROM pgmq.archive('my_queue', 1);
archive
---------
t
archive (batch)
Deletes a batch of requested messages from the specified queue and inserts them into the queue’s archive. Returns an ARRAY of message ids that were successfully archived.
pgmq.archive(queue_name text, msg_ids bigint[])
RETURNS SETOF bigint
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | msg_ids | bigint[] | Array of message IDs to archive |
Examples:
Delete messages with ID 1 and 2 from queue my_queue and move to the archive.
SELECT * FROM pgmq.archive('my_queue', ARRAY[1, 2]);
archive
---------
1
2
Delete messages 4, which exists and 999, which does not exist.
select * from pgmq.archive('my_queue', ARRAY[4, 999]);
archive
---------
4
Queue Management
create
Create a new queue.
pgmq.create(queue_name text)
RETURNS VOID
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue |
Example:
select from pgmq.create('my_queue');
create
--------
create_partitioned
Create a partitioned queue.
pgmq.create_partitioned (
queue-ue_name text,
partition_interval text DEFAULT '10000'::text,
retention_interval text DEFAULT '100000'::text
)
RETURNS void
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | partition_interval | text | The name of the queue | | retention_interval | text | The name of the queue |
Example:
Create a queue with 100,000 messages per partition, and will retain 10,000,000 messages on old partitions. Partitions greater than this will be deleted.
select from pgmq.create_partitioned(
'my_partitioned_queue',
'100000',
'10000000'
);
create_partitioned
--------------------
create_unlogged
Creates an unlogged table. This is useful when write throughput is more important that durability. See Postgres documentation for unlogged tables for more information.
pgmq.create_unlogged(queue_name text)
RETURNS void
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue |
Example:
select pgmq.create_unlogged('my_unlogged');
create_unlogged
-----------------
detach_archive
Drop the queue’s archive table as a member of the PGMQ extension. Useful for preventing the queue’s archive table from being drop when DROP EXTENSION pgmq is executed.
This does not prevent the further archives() from appending to the archive table.
pgmq.detach_archive(queue_name text)
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue |
Example:
select * from pgmq.detach_archive('my_queue');
detach_archive
----------------
drop_queue
Deletes a queue and its archive table.
pgmq.drop_queue(queue_name text)
RETURNS boolean
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue |
Example:
select * from pgmq.drop_queue('my_unlogged');
drop_queue
------------
t
Utilities
set_vt
Sets the visibility timeout of a message to a specified time duration in the future. Returns the record of the message that was updated.
pgmq.set_vt(
queue_name text,
msg_id bigint,
vt_offset integer
)
RETURNS pgmq.message_record
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | msg_id | bigint | ID of the message to set visibility time | | vt_offset | integer | Duration from now, in seconds, that the message’s VT should be set to |
Example:
Set the visibility timeout of message 1 to 30 seconds from now.
select * from pgmq.set_vt('my_queue', 11, 30);
msg_id | read_ct | enqueued_at | vt | message
--------+---------+-------------------------------+-------------------------------+----------------------
1 | 0 | 2023-10-28 19:42:21.778741-05 | 2023-10-28 19:59:34.286462-05 | {"hello": "world_0"}
list_queues
List all the queues that currently exist.
list_queues()
RETURNS TABLE(
queue_name text,
created_at timestamp with time zone,
is_partitioned boolean,
is_unlogged boolean
)
Example:
select * from pgmq.list_queues();
queue_name | created_at | is_partitioned | is_unlogged
----------------------+-------------------------------+----------------+-------------
my_queue | 2023-10-28 14:13:17.092576-05 | f | f
my_partitioned_queue | 2023-10-28 19:47:37.098692-05 | t | f
my_unlogged | 2023-10-28 20:02:30.976109-05 | f | t
metrics
Get metrics for a specific queue.
pgmq.metrics(queue_name: text)
RETURNS TABLE(
queue_name text,
queue_length bigint,
newest_msg_age_sec integer,
oldest_msg_age_sec integer,
total_messages bigint,
scrape_time timestamp with time zone
)
Parameters:
| Parameter | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue |
Returns:
| Attribute | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | queue_length | bigint | Number of messages currently in the queue | | newest_msg_age_sec | integer | null | Age of the newest message in the queue, in seconds | | oldest_msg_age_sec | integer | null | Age of the oldest message in the queue, in seconds | | total_messages | bigint | Total number of messages that have passed through the queue over all time | | scrape_time | timestamp with time zone | The current timestamp |
Example:
select * from pgmq.metrics('my_queue');
queue_name | queue_length | newest_msg_age_sec | oldest_msg_age_sec | total_messages | scrape_time
------------+--------------+--------------------+--------------------+----------------+-------------------------------
my_queue | 16 | 2445 | 2447 | 35 | 2023-10-28 20:23:08.406259-05
metrics_all
Get metrics for all existing queues.
pgmq.metrics_all()
RETURNS TABLE(
queue_name text,
queue_length bigint,
newest_msg_age_sec integer,
oldest_msg_age_sec integer,
total_messages bigint,
scrape_time timestamp with time zone
)
Returns:
| Attribute | Type | Description | | :— | :–– | :— | | queue_name | text | The name of the queue | | queue_length | bigint | Number of messages currently in the queue | | newest_msg_age_sec | integer | null | Age of the newest message in the queue, in seconds | | oldest_msg_age_sec | integer | null | Age of the oldest message in the queue, in seconds | | total_messages | bigint | Total number of messages that have passed through the queue over all time | | scrape_time | timestamp with time zone | The current timestamp |
select * from pgmq.metrics_all();
queue_name | queue_length | newest_msg_age_sec | oldest_msg_age_sec | total_messages | scrape_time
----------------------+--------------+--------------------+--------------------+----------------+-------------------------------
my_queue | 16 | 2563 | 2565 | 35 | 2023-10-28 20:25:07.016413-05
my_partitioned_queue | 1 | 11 | 11 | 1 | 2023-10-28 20:25:07.016413-05
my_unlogged | 1 | 3 | 3 | 1 | 2023-10-28 20:25:07.016413-05