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Add facility to copy replication slots

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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
This commit is contained in:
Alvaro Herrera
2019-04-05 14:52:45 -03:00
parent de2b38419c
commit 9f06d79ef8
9 changed files with 736 additions and 50 deletions
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94
contrib/test_decoding/sql/slot.sql
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@ -76,3 +76,97 @@ SELECT slot_name FROM pg_create_physical_replication_slot('regression_slot3');
SELECT pg_replication_slot_advance('regression_slot3', '0/0'); -- invalid LSN
SELECT pg_replication_slot_advance('regression_slot3', '0/1'); -- error
SELECT pg_drop_replication_slot('regression_slot3');
--
-- Test copy functions for logical replication slots
--
-- Create and copy logical slots
SELECT 'init' FROM pg_create_logical_replication_slot('orig_slot1', 'test_decoding', false);
SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'copied_slot1_no_change');
SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'copied_slot1_change_plugin', false, 'pgoutput');
SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'copied_slot1_change_plugin_temp', true, 'pgoutput');
-- Check all copied slots status
SELECT
o.slot_name, o.plugin, o.temporary, c.slot_name, c.plugin, c.temporary
FROM
(SELECT * FROM pg_replication_slots WHERE slot_name LIKE 'orig%') as o
LEFT JOIN pg_replication_slots as c ON o.restart_lsn = c.restart_lsn AND o.confirmed_flush_lsn = c.confirmed_flush_lsn
WHERE
o.slot_name != c.slot_name
ORDER BY o.slot_name, c.slot_name;
-- Now we have maximum 4 replication slots. Check slots are properly
-- released even when raise error during creating the target slot.
SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'failed'); -- error
-- temporary slots were dropped automatically
SELECT pg_drop_replication_slot('orig_slot1');
SELECT pg_drop_replication_slot('copied_slot1_no_change');
SELECT pg_drop_replication_slot('copied_slot1_change_plugin');
-- Test based on the temporary logical slot
SELECT 'init' FROM pg_create_logical_replication_slot('orig_slot2', 'test_decoding', true);
SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot2', 'copied_slot2_no_change');
SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot2', 'copied_slot2_change_plugin', true, 'pgoutput');
SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot2', 'copied_slot2_change_plugin_temp', false, 'pgoutput');
-- Check all copied slots status
SELECT
o.slot_name, o.plugin, o.temporary, c.slot_name, c.plugin, c.temporary
FROM
(SELECT * FROM pg_replication_slots WHERE slot_name LIKE 'orig%') as o
LEFT JOIN pg_replication_slots as c ON o.restart_lsn = c.restart_lsn AND o.confirmed_flush_lsn = c.confirmed_flush_lsn
WHERE
o.slot_name != c.slot_name
ORDER BY o.slot_name, c.slot_name;
-- Cannot copy a logical slot to a physical slot
SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'failed'); -- error
-- temporary slots were dropped automatically
SELECT pg_drop_replication_slot('copied_slot2_change_plugin_temp');
--
-- Test copy functions for physical replication slots
--
-- Create and copy physical slots
SELECT 'init' FROM pg_create_physical_replication_slot('orig_slot1', true);
SELECT 'init' FROM pg_create_physical_replication_slot('orig_slot2', false);
SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot1', 'copied_slot1_no_change');
SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot1', 'copied_slot1_temp', true);
-- Check all copied slots status. Since all slots don't reserve WAL we check only other fields.
SELECT slot_name, slot_type, temporary FROM pg_replication_slots;
-- Cannot copy a physical slot to a logical slot
SELECT 'copy' FROM pg_copy_logical_replication_slot('orig_slot1', 'failed'); -- error
-- Cannot copy a physical slot that doesn't reserve WAL
SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'failed'); -- error
-- temporary slots were dropped automatically
SELECT pg_drop_replication_slot('orig_slot1');
SELECT pg_drop_replication_slot('orig_slot2');
SELECT pg_drop_replication_slot('copied_slot1_no_change');
-- Test based on the temporary physical slot
SELECT 'init' FROM pg_create_physical_replication_slot('orig_slot2', true, true);
SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'copied_slot2_no_change');
SELECT 'copy' FROM pg_copy_physical_replication_slot('orig_slot2', 'copied_slot2_notemp', false);
-- Check all copied slots status
SELECT
o.slot_name, o.temporary, c.slot_name, c.temporary
FROM
(SELECT * FROM pg_replication_slots WHERE slot_name LIKE 'orig%') as o
LEFT JOIN pg_replication_slots as c ON o.restart_lsn = c.restart_lsn
WHERE
o.slot_name != c.slot_name
ORDER BY o.slot_name, c.slot_name;
SELECT pg_drop_replication_slot('orig_slot2');
SELECT pg_drop_replication_slot('copied_slot2_no_change');
SELECT pg_drop_replication_slot('copied_slot2_notemp');