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PostgreSQL禁止的异象是什么

发表于：2024-09-22 作者：千家信息网编辑

千家信息网最后更新 2024年09月22日，这篇文章主要讲解了"PostgreSQL禁止的异象是什么"，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习"PostgreSQL禁止的异象是什么"吧！测试数

千家信息网最后更新 2024年09月22日PostgreSQL禁止的异象是什么

这篇文章主要讲解了"PostgreSQL禁止的异象是什么"，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习"PostgreSQL禁止的异象是什么"吧！

测试数据

数据表idx，在id列上有索引，数据库默认的隔离级别为可串行化

15:44:16 [local:/data/run/pg12]:5120 pg12@testdb=# \d+ idx                                         Table "public.idx" Column |       Type        | Collation | Nullable | Default | Storage  | Statstarget | Description--------+-------------------+-----------+----------+---------+----------+--------------+------------- id     | integer           |           |          |         | plain    |       | c1     | character varying |           |          |         | extended |       |Indexes:    "idx_id" btree (id)Access method: heap[pg12@localhost pg122db]$ grep 'isolation' postgresql.confdefault_transaction_isolation = 'SERIALIZABLE'

Write触发

操作序列如下：

时间点	T1	T2	T3
t1	begin;
t2	select * from idx where id = 1;
t3		begin;
t4		select * from idx where id = 10000;
t5			begin;
t6			update idx set c1 = 'x' where id = 10000;
t7			commit;
t8		update idx set c1 = 'x' where id = 1;

session 2（T2）在执行update操作时会报错

-- session 215:46:52 [local:/data/run/pg12]:5120 pg12@testdb=#* update idx set c1 = 'x' where id = 1;ERROR:  could not serialize access due to read/write dependencies among transactionsDETAIL:  Reason code: Canceled on identification as a pivot, during write.HINT:  The transaction might succeed if retried.15:47:10 [local:/data/run/pg12]:5120 pg12@testdb=#!

Read触发

操作序列如下：

时间点	T1	T2	T3
t1	begin;
t2	select * from idx where id = 1;
t3		begin;
t4		update idx set c1 = 'x1' where id = 1;
t5			begin;
t6			update idx set c1 = 'x' where id = 10000;
t7			commit;
t8		select * from idx where id = 10000;

session 2（T2）在执行select操作时会报错

15:54:41 [local:/data/run/pg12]:5120 pg12@testdb=#* select * from idx where id = 10000;ERROR:  could not serialize access due to read/write dependencies among transactionsDETAIL:  Reason code: Canceled on conflict out to pivot 423284, during read.HINT:  The transaction might succeed if retried.15:55:16 [local:/data/run/pg12]:5120 pg12@testdb=#!

commit触发

操作序列如下：

时间点	T1	T2
t1	begin;
t2	select * from idx where id = 1;
t3	update tbl set c1 = 'x' where id = 10000;
t4		begin;
t5		select * from idx where id = 10000;
t6		update idx set c1 = 'x' where id = 1;
t7		commit;
t8	commit;

T1执行commit的时候会报错：

16:07:50 [local:/data/run/pg12]:5120 pg12@testdb=#* commit;ERROR:  could not serialize access due to read/write dependencies among transactionsDETAIL:  Reason code: Canceled on identification as a pivot, during commit attempt.HINT:  The transaction might succeed if retried.

感谢各位的阅读，以上就是"PostgreSQL禁止的异象是什么"的内容了，经过本文的学习后，相信大家对PostgreSQL禁止的异象是什么这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是，小编将为大家推送更多相关知识点的文章，欢迎关注！

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