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Add facility to copy replication slots
This allows the user to create duplicates of existing replication slots, either logical or physical, and even changing properties such as whether they are temporary or the output plugin used. There are multiple uses for this, such as initializing multiple replicas using the slot for one base backup; when doing investigation of logical replication issues; and to select a different output plugins. Author: Masahiko Sawada Reviewed-by: Michael Paquier, Andres Freund, Petr Jelinek Discussion: https://postgr.es/m/CAD21AoAm7XX8y_tOPP6j4Nzzch12FvA1wPqiO690RCk+uYVstg@mail.gmail.com
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‎contrib/test_decoding/expected/slot.out‎

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@@ -150,3 +150,237 @@ SELECT pg_drop_replication_slot('regression_slot3');
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(1 row)
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--
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-- Test copy functions for logical replication slots
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--
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-- Create and copy logical slots
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SELECT 'init' FROM pg_create_logical_replication_slot('orig_slot1', 'test_decoding', false);
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?column?
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----------
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init
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(1 row)
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'copied_slot1_no_change');
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?column?
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----------
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copy
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(1 row)
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'copied_slot1_change_plugin', false, 'pgoutput');
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?column?
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----------
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copy
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(1 row)
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'copied_slot1_change_plugin_temp', true, 'pgoutput');
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?column?
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----------
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copy
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(1 row)
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-- Check all copied slots status
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SELECT
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o.slot_name, o.plugin, o.temporary, c.slot_name, c.plugin, c.temporary
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FROM
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(SELECT * FROM pg_replication_slots WHERE slot_name LIKE 'orig%') as o
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LEFT JOIN pg_replication_slots as c ON o.restart_lsn = c.restart_lsn AND o.confirmed_flush_lsn = c.confirmed_flush_lsn
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WHERE
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o.slot_name != c.slot_name
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ORDER BY o.slot_name, c.slot_name;
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slot_name | plugin | temporary | slot_name | plugin | temporary
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------------+---------------+-----------+---------------------------------+---------------+-----------
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orig_slot1 | test_decoding | f | copied_slot1_change_plugin | pgoutput | f
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orig_slot1 | test_decoding | f | copied_slot1_change_plugin_temp | pgoutput | t
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orig_slot1 | test_decoding | f | copied_slot1_no_change | test_decoding | f
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(3 rows)
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-- Now we have maximum 4 replication slots. Check slots are properly
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-- released even when raise error during creating the target slot.
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'failed'); -- error
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ERROR: all replication slots are in use
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HINT: Free one or increase max_replication_slots.
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-- temporary slots were dropped automatically
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SELECT pg_drop_replication_slot('orig_slot1');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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SELECT pg_drop_replication_slot('copied_slot1_no_change');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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SELECT pg_drop_replication_slot('copied_slot1_change_plugin');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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-- Test based on the temporary logical slot
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SELECT 'init' FROM pg_create_logical_replication_slot('orig_slot2', 'test_decoding', true);
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?column?
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----------
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init
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(1 row)
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot2', 'copied_slot2_no_change');
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?column?
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----------
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copy
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(1 row)
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot2', 'copied_slot2_change_plugin', true, 'pgoutput');
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?column?
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----------
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copy
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(1 row)
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot2', 'copied_slot2_change_plugin_temp', false, 'pgoutput');
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?column?
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----------
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copy
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(1 row)
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-- Check all copied slots status
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SELECT
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o.slot_name, o.plugin, o.temporary, c.slot_name, c.plugin, c.temporary
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FROM
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(SELECT * FROM pg_replication_slots WHERE slot_name LIKE 'orig%') as o
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LEFT JOIN pg_replication_slots as c ON o.restart_lsn = c.restart_lsn AND o.confirmed_flush_lsn = c.confirmed_flush_lsn
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WHERE
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o.slot_name != c.slot_name
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ORDER BY o.slot_name, c.slot_name;
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slot_name | plugin | temporary | slot_name | plugin | temporary
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------------+---------------+-----------+---------------------------------+---------------+-----------
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orig_slot2 | test_decoding | t | copied_slot2_change_plugin | pgoutput | t
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orig_slot2 | test_decoding | t | copied_slot2_change_plugin_temp | pgoutput | f
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orig_slot2 | test_decoding | t | copied_slot2_no_change | test_decoding | t
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(3 rows)
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-- Cannot copy a logical slot to a physical slot
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'failed'); -- error
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ERROR: cannot copy physical replication slot "orig_slot2" as a logical replication slot
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-- temporary slots were dropped automatically
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SELECT pg_drop_replication_slot('copied_slot2_change_plugin_temp');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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--
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-- Test copy functions for physical replication slots
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--
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-- Create and copy physical slots
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SELECT 'init' FROM pg_create_physical_replication_slot('orig_slot1', true);
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?column?
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----------
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init
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(1 row)
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SELECT 'init' FROM pg_create_physical_replication_slot('orig_slot2', false);
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?column?
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----------
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init
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(1 row)
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot1', 'copied_slot1_no_change');
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?column?
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----------
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copy
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(1 row)
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot1', 'copied_slot1_temp', true);
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?column?
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----------
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copy
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(1 row)
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-- Check all copied slots status. Since all slots don't reserve WAL we check only other fields.
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SELECT slot_name, slot_type, temporary FROM pg_replication_slots;
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slot_name | slot_type | temporary
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------------------------+-----------+-----------
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orig_slot1 | physical | f
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orig_slot2 | physical | f
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copied_slot1_no_change | physical | f
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copied_slot1_temp | physical | t
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(4 rows)
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-- Cannot copy a physical slot to a logical slot
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'failed'); -- error
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ERROR: cannot copy logical replication slot "orig_slot1" as a physical replication slot
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-- Cannot copy a physical slot that doesn't reserve WAL
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'failed'); -- error
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ERROR: cannot copy a replication slot that doesn't reserve WAL
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-- temporary slots were dropped automatically
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SELECT pg_drop_replication_slot('orig_slot1');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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SELECT pg_drop_replication_slot('orig_slot2');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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SELECT pg_drop_replication_slot('copied_slot1_no_change');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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-- Test based on the temporary physical slot
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SELECT 'init' FROM pg_create_physical_replication_slot('orig_slot2', true, true);
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?column?
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----------
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init
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(1 row)
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'copied_slot2_no_change');
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?column?
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----------
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copy
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(1 row)
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'copied_slot2_notemp', false);
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?column?
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----------
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copy
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(1 row)
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-- Check all copied slots status
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SELECT
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o.slot_name, o.temporary, c.slot_name, c.temporary
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FROM
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(SELECT * FROM pg_replication_slots WHERE slot_name LIKE 'orig%') as o
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LEFT JOIN pg_replication_slots as c ON o.restart_lsn = c.restart_lsn
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WHERE
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o.slot_name != c.slot_name
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ORDER BY o.slot_name, c.slot_name;
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slot_name | temporary | slot_name | temporary
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------------+-----------+------------------------+-----------
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orig_slot2 | t | copied_slot2_no_change | t
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orig_slot2 | t | copied_slot2_notemp | f
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(2 rows)
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SELECT pg_drop_replication_slot('orig_slot2');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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SELECT pg_drop_replication_slot('copied_slot2_no_change');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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SELECT pg_drop_replication_slot('copied_slot2_notemp');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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‎contrib/test_decoding/sql/slot.sql‎

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Original file line numberDiff line numberDiff line change
@@ -76,3 +76,97 @@ SELECT slot_name FROM pg_create_physical_replication_slot('regression_slot3');
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SELECT pg_replication_slot_advance('regression_slot3', '0/0'); -- invalid LSN
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SELECT pg_replication_slot_advance('regression_slot3', '0/1'); -- error
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SELECT pg_drop_replication_slot('regression_slot3');
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--
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-- Test copy functions for logical replication slots
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--
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-- Create and copy logical slots
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SELECT 'init' FROM pg_create_logical_replication_slot('orig_slot1', 'test_decoding', false);
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'copied_slot1_no_change');
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'copied_slot1_change_plugin', false, 'pgoutput');
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'copied_slot1_change_plugin_temp', true, 'pgoutput');
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-- Check all copied slots status
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SELECT
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o.slot_name, o.plugin, o.temporary, c.slot_name, c.plugin, c.temporary
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FROM
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(SELECT * FROM pg_replication_slots WHERE slot_name LIKE 'orig%') as o
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LEFT JOIN pg_replication_slots as c ON o.restart_lsn = c.restart_lsn AND o.confirmed_flush_lsn = c.confirmed_flush_lsn
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WHERE
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o.slot_name != c.slot_name
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ORDER BY o.slot_name, c.slot_name;
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-- Now we have maximum 4 replication slots. Check slots are properly
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-- released even when raise error during creating the target slot.
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'failed'); -- error
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-- temporary slots were dropped automatically
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SELECT pg_drop_replication_slot('orig_slot1');
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SELECT pg_drop_replication_slot('copied_slot1_no_change');
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SELECT pg_drop_replication_slot('copied_slot1_change_plugin');
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-- Test based on the temporary logical slot
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SELECT 'init' FROM pg_create_logical_replication_slot('orig_slot2', 'test_decoding', true);
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot2', 'copied_slot2_no_change');
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot2', 'copied_slot2_change_plugin', true, 'pgoutput');
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot2', 'copied_slot2_change_plugin_temp', false, 'pgoutput');
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-- Check all copied slots status
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SELECT
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o.slot_name, o.plugin, o.temporary, c.slot_name, c.plugin, c.temporary
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FROM
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(SELECT * FROM pg_replication_slots WHERE slot_name LIKE 'orig%') as o
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LEFT JOIN pg_replication_slots as c ON o.restart_lsn = c.restart_lsn AND o.confirmed_flush_lsn = c.confirmed_flush_lsn
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WHERE
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o.slot_name != c.slot_name
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ORDER BY o.slot_name, c.slot_name;
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-- Cannot copy a logical slot to a physical slot
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'failed'); -- error
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-- temporary slots were dropped automatically
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SELECT pg_drop_replication_slot('copied_slot2_change_plugin_temp');
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--
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-- Test copy functions for physical replication slots
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--
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-- Create and copy physical slots
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SELECT 'init' FROM pg_create_physical_replication_slot('orig_slot1', true);
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SELECT 'init' FROM pg_create_physical_replication_slot('orig_slot2', false);
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot1', 'copied_slot1_no_change');
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot1', 'copied_slot1_temp', true);
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-- Check all copied slots status. Since all slots don't reserve WAL we check only other fields.
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SELECT slot_name, slot_type, temporary FROM pg_replication_slots;
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-- Cannot copy a physical slot to a logical slot
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SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'failed'); -- error
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-- Cannot copy a physical slot that doesn't reserve WAL
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'failed'); -- error
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-- temporary slots were dropped automatically
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SELECT pg_drop_replication_slot('orig_slot1');
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SELECT pg_drop_replication_slot('orig_slot2');
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SELECT pg_drop_replication_slot('copied_slot1_no_change');
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-- Test based on the temporary physical slot
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SELECT 'init' FROM pg_create_physical_replication_slot('orig_slot2', true, true);
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'copied_slot2_no_change');
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SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'copied_slot2_notemp', false);
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-- Check all copied slots status
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SELECT
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o.slot_name, o.temporary, c.slot_name, c.temporary
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FROM
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(SELECT * FROM pg_replication_slots WHERE slot_name LIKE 'orig%') as o
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LEFT JOIN pg_replication_slots as c ON o.restart_lsn = c.restart_lsn
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WHERE
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o.slot_name != c.slot_name
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ORDER BY o.slot_name, c.slot_name;
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SELECT pg_drop_replication_slot('orig_slot2');
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SELECT pg_drop_replication_slot('copied_slot2_no_change');
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SELECT pg_drop_replication_slot('copied_slot2_notemp');

‎doc/src/sgml/func.sgml‎

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Original file line numberDiff line numberDiff line change
@@ -20431,6 +20431,47 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
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</entry>
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</row>
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<row>
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<entry>
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<indexterm>
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<primary>pg_copy_physical_replication_slot</primary>
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</indexterm>
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<literal><function>pg_copy_physical_replication_slot(<parameter>src_slot_name</parameter> <type>name</type>, <parameter>dst_slot_name</parameter> <type>name</type> <optional>, <parameter>temporary</parameter> <type>boolean</type></optional>)</function></literal>
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</entry>
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<entry>
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(<parameter>slot_name</parameter> <type>name</type>, <parameter>lsn</parameter> <type>pg_lsn</type>)
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</entry>
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<entry>
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Copies an existing physical replication slot name <parameter>src_slot_name</parameter>
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to a physical replication slot named <parameter>dst_slot_name</parameter>.
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The copied physical slot starts to reserve WAL from the same <acronym>LSN</acronym> as the
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source slot.
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<parameter>temporary</parameter> is optional. If <parameter>temporary</parameter>
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is omitted, the same value as the source slot is used.
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</entry>
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</row>
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<row>
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<entry>
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<indexterm>
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<primary>pg_copy_logical_replication_slot</primary>
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</indexterm>
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<literal><function>pg_copy_logical_replication_slot(<parameter>src_slot_name</parameter> <type>name</type>, <parameter>dst_slot_name</parameter> <type>name</type> <optional>, <parameter>temporary</parameter> <type>boolean</type> <optional>, <parameter>plugin</parameter> <type>name</type></optional></optional>)</function></literal>
20460+
</entry>
20461+
<entry>
20462+
(<parameter>slot_name</parameter> <type>name</type>, <parameter>lsn</parameter> <type>pg_lsn</type>)
20463+
</entry>
20464+
<entry>
20465+
Copies an existing logical replication slot name <parameter>src_slot_name</parameter>
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to a logical replication slot named <parameter>dst_slot_name</parameter>
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while changing the output plugin and persistence. The copied logical slot starts
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from the same <acronym>LSN</acronym> as the source logical slot. Both
20469+
<parameter>temporary</parameter> and <parameter>plugin</parameter> are optional.
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If <parameter>temporary</parameter> or <parameter>plugin</parameter> are omitted,
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the same values as the source logical slot are used.
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</entry>
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</row>
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<row>
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<entry>
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<indexterm>

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