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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.
91 lines
4.2 KiB
Plaintext
91 lines
4.2 KiB
Plaintext
-- predictability
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SET synchronous_commit = on;
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DROP TABLE IF EXISTS xpto;
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NOTICE: table "xpto" does not exist, skipping
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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 SEQUENCE xpto_rand_seq START 79 INCREMENT 1499; -- portable "random"
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CREATE TABLE xpto (
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id serial primary key,
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toasted_col1 text,
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rand1 float8 DEFAULT nextval('xpto_rand_seq'),
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toasted_col2 text,
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rand2 float8 DEFAULT nextval('xpto_rand_seq')
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);
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-- uncompressed external toast data
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INSERT INTO xpto (toasted_col1, toasted_col2) SELECT string_agg(g.i::text, ''), string_agg((g.i*2)::text, '') FROM generate_series(1, 2000) g(i);
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-- compressed external toast data
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INSERT INTO xpto (toasted_col2) SELECT repeat(string_agg(to_char(g.i, 'FM0000'), ''), 50) FROM generate_series(1, 500) g(i);
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-- update of existing column
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UPDATE xpto SET toasted_col1 = (SELECT string_agg(g.i::text, '') FROM generate_series(1, 2000) g(i)) WHERE id = 1;
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UPDATE xpto SET rand1 = 123.456 WHERE id = 1;
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DELETE FROM xpto WHERE id = 1;
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DROP TABLE IF EXISTS toasted_key;
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NOTICE: table "toasted_key" does not exist, skipping
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CREATE TABLE toasted_key (
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id serial,
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toasted_key text PRIMARY KEY,
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toasted_col1 text,
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toasted_col2 text
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);
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ALTER TABLE toasted_key ALTER COLUMN toasted_key SET STORAGE EXTERNAL;
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ALTER TABLE toasted_key ALTER COLUMN toasted_col1 SET STORAGE EXTERNAL;
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INSERT INTO toasted_key(toasted_key, toasted_col1) VALUES(repeat('1234567890', 200), repeat('9876543210', 200));
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-- test update of a toasted key without changing it
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UPDATE toasted_key SET toasted_col2 = toasted_col1;
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-- test update of a toasted key, changing it
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UPDATE toasted_key SET toasted_key = toasted_key || '1';
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DELETE FROM toasted_key;
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SELECT substr(data, 1, 200) FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0');
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substr
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----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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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.xpto: INSERT: id[integer]:1 toasted_col1[text]:'1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374
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COMMIT
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BEGIN
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table public.xpto: INSERT: id[integer]:2 toasted_col1[text]:null rand1[double precision]:3077 toasted_col2[text]:'00010002000300040005000600070008000900100011001200130014001500160017001800190020002100
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COMMIT
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BEGIN
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table public.xpto: UPDATE: id[integer]:1 toasted_col1[text]:'1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374
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COMMIT
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BEGIN
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table public.xpto: UPDATE: id[integer]:1 toasted_col1[text]:unchanged-toast-datum rand1[double precision]:123.456 toasted_col2[text]:unchanged-toast-datum rand2[double precision]:1578
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COMMIT
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BEGIN
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table public.xpto: DELETE: id[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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table public.toasted_key: INSERT: id[integer]:1 toasted_key[text]:'1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123
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COMMIT
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BEGIN
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table public.toasted_key: UPDATE: id[integer]:1 toasted_key[text]:unchanged-toast-datum toasted_col1[text]:unchanged-toast-datum toasted_col2[text]:'987654321098765432109876543210987654321098765432109
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COMMIT
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BEGIN
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table public.toasted_key: UPDATE: old-key: toasted_key[text]:'123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678
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COMMIT
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BEGIN
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table public.toasted_key: DELETE: toasted_key[text]:'123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567
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COMMIT
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(37 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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