Re: [BUGS] BUG #14691: Isolation failure in deferrable transactionconcurrent with schema change
| От | David G. Johnston |
|---|---|
| Тема | Re: [BUGS] BUG #14691: Isolation failure in deferrable transactionconcurrent with schema change |
| Дата | |
| Msg-id | CAKFQuwZayi_XSjgR+xoB+Sogv51fYrV5vghgwxVTkbY15nS_Tg@mail.gmail.com обсуждение исходный текст |
| Ответ на | [BUGS] BUG #14691: Isolation failure in deferrable transaction concurrentwith schema change (cpacejo@clearskydata.com) |
| Ответы |
Re: [BUGS] BUG #14691: Isolation failure in deferrable transactionconcurrent with schema change
Re: [BUGS] BUG #14691: Isolation failure in deferrable transactionconcurrent with schema change |
| Список | pgsql-bugs |
The following bug has been logged on the website:
Bug reference: 14691
Logged by: Chris Pacejo
Email address: cpacejo@clearskydata.com
PostgreSQL version: 9.5.7
Operating system: CentOS 7
Description:
Hi, issuing a SERIALIZABLE DEFERRABLE READ ONLY read from a table to which a
column is being added results in an isolation failure.
me=> BEGIN; ALTER TABLE foo ADD COLUMN y integer DEFAULT 0;
me=> BEGIN; ALTER TABLE foo ADD COLUMN y integer; UPDATE foo SET y = 0;
x | y
---+---
1 |
2 |
3 |
(3 rows)
This is a documented limitation.
"Some DDL commands, currently only TRUNCATE and the table-rewriting forms of ALTER TABLE, are not MVCC-safe."
The first command is "table-rewriting".
The second ALTER TABLE doesn't rewrite the table but does change its structure - so you get rows but the newly added column is null. This would seem to be a reasonable behavior.
David J.
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