RE: Timeout parameters

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От MikalaiKeida@ibagroup.eu
Тема RE: Timeout parameters
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Msg-id OF8503B6B7.A2DC877F-ON432583BE.00275173-432583BE.0028ECF7@iba.by
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Ответ на RE: Timeout parameters  ("Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com>)
Ответы RE: Timeout parameters
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Hello Takayuki-san,

> Yes, so I think it would be necessary to describe how to set socket_timeout with relation to other timeout parameters -- socket_timeout > statement_timeout, emphasizing that socket_timeout is not for canceling long-running queries but for returning control to the client.

For me it does not look enough.
If you would like to implement the 'socket_timeout' parameter, could you pay attention on the Fabien Coelho comment?

> The fact that no answer data is received may mean that it takes time to
> compute the result, so cancelling seems appropriate to me, rather than
> severing the connection and starting a new one immediately, leaving the
> server loaded with its query.


This comment is very important to pay attention on.
Let's imagine once more:
1. end-user makes a query

2. the query has not completed within this timeout due to any reason: the query is too 'heavy', some problem with OS happened, PostgreSQL server terminated
3. if we simple close connection, the first case is negative by mistake. To avoid such a situation I think it would be better to call a PQcancel(). In case of failure PQcancel() terminates in 'socket_timeout'. So, control to the end-user in such a failure situation will be returned in 2 * 'socket_timeout' interval. It is much better than hanging forever in some specific cases. Moreover, such solution will not lead to the overloading of PostgreSQL server by abnormally ignored 'heavy' queries results by end-users.

What do you think about it?


Best regards,
Mikalai Keida

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