От: Kevin Grittner
Тема: Re: the XID question
Дата: ,
Msg-id: 4D36A35302000025000397CC@gw.wicourts.gov
(см: обсуждение, исходный текст)
Ответ на: Re: the XID question  (Filip Rembiałkowski)
Список: pgsql-performance

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the XID question  ("Charles.Hou", )
 Re: the XID question  ("Charles.Hou", )
 Re: the XID question  (Filip Rembiałkowski, )
  Re: the XID question  ("Kevin Grittner", )
 Re: the XID question  (Chris Browne, )
  Re: the XID question  (Andres Freund, )
   Re: the XID question  ("Kevin Grittner", )
    Re: the XID question  (Greg Smith, )
 Re: the XID question  ("Charles.Hou", )
  Re: the XID question  ("Kevin Grittner", )
   Re: the XID question  (Robert Haas, )
 Re: the XID question  ("Charles.Hou", )

Filip Rembia*kowski<> wrote:
> 2011/1/19 Charles.Hou <>:

>> " select * from mybook" SQL command also increase the XID ?
>
> Yes. Single SELECT is a transaction. Hence, it needs a transaction
> ID.

No, not in recent versions of PostgreSQL.  There's virtual
transaction ID, too; which is all that's needed unless the
transaction writes something.

Also, as a fine point, if you use explicit database transactions
(with BEGIN or START TRANSACTION) then you normally get one XID for
the entire transaction, unless you use SAVEPOINTs.

-Kevin


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