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b89e151054
This feature, building on previous commits, allows the write-ahead log stream to be decoded into a series of logical changes; that is, inserts, updates, and deletes and the transactions which contain them. It is capable of handling decoding even across changes to the schema of the effected tables. The output format is controlled by a so-called "output plugin"; an example is included. To make use of this in a real replication system, the output plugin will need to be modified to produce output in the format appropriate to that system, and to perform filtering. Currently, information can be extracted from the logical decoding system only via SQL; future commits will add the ability to stream changes via walsender. Andres Freund, with review and other contributions from many other people, including Álvaro Herrera, Abhijit Menon-Sen, Peter Gheogegan, Kevin Grittner, Robert Haas, Heikki Linnakangas, Fujii Masao, Abhijit Menon-Sen, Michael Paquier, Simon Riggs, Craig Ringer, and Steve Singer.
108 lines
3.9 KiB
Plaintext
108 lines
3.9 KiB
Plaintext
-- predictability
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SET synchronous_commit = on;
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DROP TABLE IF EXISTS replication_example;
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SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
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?column?
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----------
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init
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(1 row)
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CREATE TABLE replication_example(id SERIAL PRIMARY KEY, somedata int, text varchar(120));
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INSERT INTO replication_example(somedata) VALUES (1);
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SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0');
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data
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----------------------------------------------------------------------------------------------------------
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BEGIN
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COMMIT
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BEGIN
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table public.replication_example: INSERT: id[integer]:1 somedata[integer]:1 text[character varying]:null
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COMMIT
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(5 rows)
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BEGIN;
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INSERT INTO replication_example(somedata) VALUES (2);
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ALTER TABLE replication_example ADD COLUMN testcolumn1 int;
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INSERT INTO replication_example(somedata, testcolumn1) VALUES (3, 1);
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COMMIT;
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BEGIN;
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INSERT INTO replication_example(somedata) VALUES (3);
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ALTER TABLE replication_example ADD COLUMN testcolumn2 int;
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INSERT INTO replication_example(somedata, testcolumn1, testcolumn2) VALUES (4, 2, 1);
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COMMIT;
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VACUUM FULL pg_am;
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VACUUM FULL pg_amop;
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VACUUM FULL pg_proc;
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VACUUM FULL pg_opclass;
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VACUUM FULL pg_type;
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VACUUM FULL pg_index;
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VACUUM FULL pg_database;
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-- repeated rewrites that fail
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BEGIN;
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CLUSTER pg_class USING pg_class_oid_index;
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CLUSTER pg_class USING pg_class_oid_index;
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ROLLBACK;
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-- repeated rewrites that succeed
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BEGIN;
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CLUSTER pg_class USING pg_class_oid_index;
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CLUSTER pg_class USING pg_class_oid_index;
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CLUSTER pg_class USING pg_class_oid_index;
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COMMIT;
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-- repeated rewrites in different transactions
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VACUUM FULL pg_class;
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VACUUM FULL pg_class;
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INSERT INTO replication_example(somedata, testcolumn1) VALUES (5, 3);
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BEGIN;
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INSERT INTO replication_example(somedata, testcolumn1) VALUES (6, 4);
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ALTER TABLE replication_example ADD COLUMN testcolumn3 int;
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INSERT INTO replication_example(somedata, testcolumn1, testcolumn3) VALUES (7, 5, 1);
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COMMIT;
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-- make old files go away
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CHECKPOINT;
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SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0');
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data
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----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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BEGIN
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table public.replication_example: INSERT: id[integer]:2 somedata[integer]:2 text[character varying]:null
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table public.replication_example: INSERT: id[integer]:3 somedata[integer]:3 text[character varying]:null testcolumn1[integer]:1
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COMMIT
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BEGIN
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table public.replication_example: INSERT: id[integer]:4 somedata[integer]:3 text[character varying]:null testcolumn1[integer]:null
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table public.replication_example: INSERT: id[integer]:5 somedata[integer]:4 text[character varying]:null testcolumn1[integer]:2 testcolumn2[integer]:1
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COMMIT
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BEGIN
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COMMIT
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BEGIN
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COMMIT
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BEGIN
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COMMIT
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BEGIN
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COMMIT
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BEGIN
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COMMIT
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BEGIN
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COMMIT
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BEGIN
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COMMIT
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BEGIN
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COMMIT
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BEGIN
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COMMIT
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BEGIN
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COMMIT
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BEGIN
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table public.replication_example: INSERT: id[integer]:6 somedata[integer]:5 text[character varying]:null testcolumn1[integer]:3 testcolumn2[integer]:null
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COMMIT
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BEGIN
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table public.replication_example: INSERT: id[integer]:7 somedata[integer]:6 text[character varying]:null testcolumn1[integer]:4 testcolumn2[integer]:null
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table public.replication_example: INSERT: id[integer]:8 somedata[integer]:7 text[character varying]:null testcolumn1[integer]:5 testcolumn2[integer]:null testcolumn3[integer]:1
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COMMIT
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(35 rows)
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SELECT pg_drop_replication_slot('regression_slot');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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DROP TABLE IF EXISTS replication_example;
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