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2633dae2e4
This commit standardizes the output format for LSNs to ensure consistent representation across various tools and messages. Previously, LSNs were inconsistently printed as `%X/%X` in some contexts, while others used zero-padding. This often led to confusion when comparing. To address this, the LSN format is now uniformly set to `%X/%08X`, ensuring the lower 32-bit part is always zero-padded to eight hexadecimal digits. Author: Japin Li <japinli@hotmail.com> Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com> Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de> Discussion: https://postgr.es/m/ME0P300MB0445CA53CA0E4B8C1879AF84B641A@ME0P300MB0445.AUSP300.PROD.OUTLOOK.COM
65 lines
2.3 KiB
Plaintext
65 lines
2.3 KiB
Plaintext
<!-- doc/src/sgml/test-decoding.sgml -->
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<sect1 id="test-decoding" xreflabel="test_decoding">
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<title>test_decoding — SQL-based test/example module for WAL logical decoding</title>
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<indexterm zone="test-decoding">
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<primary>test_decoding</primary>
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</indexterm>
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<para>
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<filename>test_decoding</filename> is an example of a logical decoding
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output plugin. It doesn't do anything especially useful, but can serve as
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a starting point for developing your own output plugin.
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</para>
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<para>
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<filename>test_decoding</filename> receives WAL through the logical decoding
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mechanism and decodes it into text representations of the operations
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performed.
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</para>
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<para>
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Typical output from this plugin, used over the SQL logical decoding
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interface, might be:
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<programlisting>
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postgres=# SELECT * FROM pg_logical_slot_get_changes('test_slot', NULL, NULL, 'include-xids', '0');
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lsn | xid | data
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------------+-----+--------------------------------------------------
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0/016D30F8 | 691 | BEGIN
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0/016D32A0 | 691 | table public.data: INSERT: id[int4]:2 data[text]:'arg'
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0/016D32A0 | 691 | table public.data: INSERT: id[int4]:3 data[text]:'demo'
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0/016D32A0 | 691 | COMMIT
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0/016D32D8 | 692 | BEGIN
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0/016D3398 | 692 | table public.data: DELETE: id[int4]:2
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0/016D3398 | 692 | table public.data: DELETE: id[int4]:3
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0/016D3398 | 692 | COMMIT
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(8 rows)
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</programlisting>
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</para>
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<para>
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We can also get the changes of the in-progress transaction, and the typical
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output might be:
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<programlisting>
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postgres[33712]=#* SELECT * FROM pg_logical_slot_get_changes('test_slot', NULL, NULL, 'stream-changes', '1');
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lsn | xid | data
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------------+-----+--------------------------------------------------
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0/016B21F8 | 503 | opening a streamed block for transaction TXN 503
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0/016B21F8 | 503 | streaming change for TXN 503
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0/016B2300 | 503 | streaming change for TXN 503
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0/016B2408 | 503 | streaming change for TXN 503
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0/016BEBA0 | 503 | closing a streamed block for transaction TXN 503
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0/016B21F8 | 503 | opening a streamed block for transaction TXN 503
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0/016BECA8 | 503 | streaming change for TXN 503
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0/016BEDB0 | 503 | streaming change for TXN 503
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0/016BEEB8 | 503 | streaming change for TXN 503
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0/016BEBA0 | 503 | closing a streamed block for transaction TXN 503
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(10 rows)
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</programlisting>
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</para>
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</sect1>
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