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The original titles only had the module name, which is not very useful when scanning the list. By adding a very brief description to each title, the table of contents becomes friendlier. Also amend the introduction in the "additional modules" appendix, using the word "Extension" more extensively. Nowadays, almost all contrib modules are extensions, so this is also helpful. Author: Karl O. Pinc <kop@karlpinc.com> Reviewed-by: Brar Piening <brar@gmx.de> Discussion: https://postgr.es/m/20230102180015.372995a9@slate.karlpinc.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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0/16D30F8 | 691 | BEGIN
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0/16D32A0 | 691 | table public.data: INSERT: id[int4]:2 data[text]:'arg'
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0/16D32A0 | 691 | table public.data: INSERT: id[int4]:3 data[text]:'demo'
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0/16D32A0 | 691 | COMMIT
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0/16D32D8 | 692 | BEGIN
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0/16D3398 | 692 | table public.data: DELETE: id[int4]:2
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0/16D3398 | 692 | table public.data: DELETE: id[int4]:3
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0/16D3398 | 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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0/16B21F8 | 503 | opening a streamed block for transaction TXN 503
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0/16B21F8 | 503 | streaming change for TXN 503
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0/16B2300 | 503 | streaming change for TXN 503
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0/16B2408 | 503 | streaming change for TXN 503
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0/16BEBA0 | 503 | closing a streamed block for transaction TXN 503
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0/16B21F8 | 503 | opening a streamed block for transaction TXN 503
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0/16BECA8 | 503 | streaming change for TXN 503
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0/16BEDB0 | 503 | streaming change for TXN 503
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0/16BEEB8 | 503 | streaming change for TXN 503
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0/16BEBA0 | 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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