关于原子引擎的交换声明是否为多个表提供原子能？

发布于 2025-02-03 09:41:53 字数 468 浏览 1 评论 0原文

文档声明原子质用于交换两个表格，但是多个表格呢？以下查询效果很好，并在表中执行交换a＆lt; =＆gt; b和c＆lt; =＆gt; D：

EXCHANGE TABLES "default"."A" AND "default"."B", "default"."C" AND "default"."D"

关于原子引擎的交换语句是否为多个表提供原子能吗？当a＆lt; =＆gt;时可能是情况。 b交换但c＆lt; =＆gt; D不是吗？原子性在整个交换查询上会传播吗？

原文

Documentation declares Atomicity for exchanging two tables, but what about multiple tables? Following query works well and perform exchanging within tables A <=> B and C <=> D:

EXCHANGE TABLES "default"."A" AND "default"."B", "default"."C" AND "default"."D"

Does EXCHANGE statement on Atomic engine provide atomic capabilities for multiple tables?
Can be situation when A <=> B exchanged but C <=> D not? Does atomicity spreads on whole EXCHANGE query?

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恏ㄋ傷疤忘ㄋ疼 2025-02-10 09:41:53

他们不是原子。

insert into a.x1 select 1;
insert into a.x1 select 2;

exchange tables a.x1 and a.x2, a.y1 and a.y2;

Received exception from server (version 22.6.1):
Code: 521. DB::Exception: Received from localhost:9000.DB::ErrnoException: Paths cannot be exchanged because /var/lib/clickhouse/store/209/209474d2-5d64-4ca0-8b45-9abf4109235a/y1.sql or /var/lib/clickhouse/store/209/209474d2-5d64-4ca0-8b45-9abf4109235a/y2.sql does not exist, errno: 2, strerror: No such file or directory. (ATOMIC_RENAME_FAIL)

select * from a.x1;
Ok.
0 rows in set. Elapsed: 0.002 sec.


select * from a.x2
┌─A─┐
│ 2 │
└───┘
┌─A─┐
│ 1 │
└───┘

原子与DML交易无关。这是关于选择的可见性。该查询没有看到中间状态，也不会投掷表。不存在...

They are not atomic.

insert into a.x1 select 1;
insert into a.x1 select 2;

exchange tables a.x1 and a.x2, a.y1 and a.y2;

Received exception from server (version 22.6.1):
Code: 521. DB::Exception: Received from localhost:9000.DB::ErrnoException: Paths cannot be exchanged because /var/lib/clickhouse/store/209/209474d2-5d64-4ca0-8b45-9abf4109235a/y1.sql or /var/lib/clickhouse/store/209/209474d2-5d64-4ca0-8b45-9abf4109235a/y2.sql does not exist, errno: 2, strerror: No such file or directory. (ATOMIC_RENAME_FAIL)

select * from a.x1;
Ok.
0 rows in set. Elapsed: 0.002 sec.


select * from a.x2
┌─A─┐
│ 2 │
└───┘
┌─A─┐
│ 1 │
└───┘

Atomicy is not about DML transactions. It's about visibility for selects. That queries do not see intermediate state and do not throw table . does not exists...

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