Re: backend pid changing

From: Matthew Wakeling
Subject: Re: backend pid changing
Date: ,
Msg-id: Pine.LNX.4.64.0806041602150.3987@aragorn.flymine.org
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In response to: backend pid changing  (Lewis Kapell)
List: pgsql-performance

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backend pid changing  (Lewis Kapell, )
 Re: backend pid changing  (Matthew Wakeling, )
 Re: backend pid changing  (Tom Lane, )
  Re: backend pid changing  (Lewis Kapell, )
   PgPool parallel query performance rules of thumb  (John Beaver, )
    Re: PgPool parallel query performance rules of thumb  ("Mason Sharp", )

On Wed, 4 Jun 2008, Lewis Kapell wrote:
> The client sends its authorization information immediately before
> sending the data, and also with the data chunk.

Well, I have no idea why the backend pid is changing, but here it looks
like you have a classic concurrency problem caused by checking a variable
twice. It seems you have client-side error recovery on the initial check,
but not on the second check. The solution is to eliminate the first check,
and implement proper error recovery on the second check, so that the
client can just get a new hash and try again.

Matthew

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