目录

pg_replication_slot_advance()

用于推进复制槽当前已确认位置的函数

pg_replication_slot_advance() 是一个系统函数，用于推进复制槽（物理或逻辑）当前已确认的位置。

pg_replication_slot_advance() 在 PostgreSQL 11 中引入。

用法

pg_replication_slot_advance ( slot_name name, upto_lsn pg_lsn ) →
        record ( slot_name name, end_lsn pg_lsn )

该槽不能向后移动，也不能移动到当前插入位置之外。

由于该槽的先前位置而保留的任何 WAL（写前日志）将在下一次 检查点 时被删除。

如果无法推进该槽，则会引发错误。

变更历史

示例

推进物理复制槽

postgres=# SELECT slot_name, slot_type, active, restart_lsn, confirmed_flush_lsn FROM pg_replication_slots\gx
-[ RECORD 1 ]-------+----------
slot_name           | node2
slot_type           | physical
active              | f
restart_lsn         | 0/301C4D8
confirmed_flush_lsn | 

postgres=# INSERT INTO foo VALUES (1, clock_timestamp());
INSERT 0 1

postgres=# SELECT * FROM pg_replication_slot_advance('node2', pg_current_wal_lsn());
 slot_name |  end_lsn  
-----------+-----------
 node2     | 0/301C5D8
(1 row)

postgres=# SELECT slot_name, slot_type, active, restart_lsn, confirmed_flush_lsn FROM pg_replication_slots\gx
-[ RECORD 1 ]-------+----------
slot_name           | node2
slot_type           | physical
active              | f
restart_lsn         | 0/301C5D8
confirmed_flush_lsn |

尝试推进一个因为从未使用或已失效而未保留 WAL 的槽

postgres=# SELECT * FROM pg_replication_slot_advance('physical_slot_1', '0/3002DE0');
ERROR:  replication slot "physical_slot_1" cannot be advanced
DETAIL:  This slot has never previously reserved WAL, or it has been invalidated.

尝试将复制槽重置到较早的位置

postgres=# SELECT * FROM pg_replication_slot_advance('test_slot_1', '0/301D4E0');
ERROR:  cannot advance replication slot to 0/301D4E0, minimum is 0/492C6A8

尝试将复制槽重置到无效的位置

postgres=# SELECT * FROM pg_replication_slot_advance('test_slot_1', '0/0');
ERROR:  invalid target WAL LSN

分类

复制, 复制槽, 系统函数, WAL

另请参阅

pg_replication_origin_advance()

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