Postgresql 中文操作指南
F.45. test_decoding — SQL-based test/example module for WAL logical decoding #
test_decoding 是逻辑解码输出插件的一个示例。它没有什么特别的用处,但可以作为开发您自己的输出插件的起点。
test_decoding 通过逻辑解码机制接收 WAL,并将其解码为所执行操作的文本表示。
此插件的典型输出(在 SQL 逻辑解码接口上使用)可能是:
postgres=# SELECT * FROM pg_logical_slot_get_changes('test_slot', NULL, NULL, 'include-xids', '0');
lsn | xid | data
-----------+-----+--------------------------------------------------
0/16D30F8 | 691 | BEGIN
0/16D32A0 | 691 | table public.data: INSERT: id[int4]:2 data[text]:'arg'
0/16D32A0 | 691 | table public.data: INSERT: id[int4]:3 data[text]:'demo'
0/16D32A0 | 691 | COMMIT
0/16D32D8 | 692 | BEGIN
0/16D3398 | 692 | table public.data: DELETE: id[int4]:2
0/16D3398 | 692 | table public.data: DELETE: id[int4]:3
0/16D3398 | 692 | COMMIT
(8 rows)
也可以获取进行中的事务的更改,并且典型的输出可能是:
postgres[33712]=#* SELECT * FROM pg_logical_slot_get_changes('test_slot', NULL, NULL, 'stream-changes', '1');
lsn | xid | data
-----------+-----+--------------------------------------------------
0/16B21F8 | 503 | opening a streamed block for transaction TXN 503
0/16B21F8 | 503 | streaming change for TXN 503
0/16B2300 | 503 | streaming change for TXN 503
0/16B2408 | 503 | streaming change for TXN 503
0/16BEBA0 | 503 | closing a streamed block for transaction TXN 503
0/16B21F8 | 503 | opening a streamed block for transaction TXN 503
0/16BECA8 | 503 | streaming change for TXN 503
0/16BEDB0 | 503 | streaming change for TXN 503
0/16BEEB8 | 503 | streaming change for TXN 503
0/16BEBA0 | 503 | closing a streamed block for transaction TXN 503
(10 rows)