Обсуждение: why we need both the collector & buffer process
<p>hi,all hackers of postgres<p> when postmaster start as a service . another two processes(collector & buffer ) starttheir work at the same time.<p> I have read the code and I am wondering why we need two processes to do the work.I think one process can work as well. Are there something special you considered when you developed this feature?<p> Best wishes!<p> William<p><br /><p><br /><hr size="1" /><b>Do You Yahoo!?</b><br /><a href="http://rd.yahoo.com/mail_cn/tag/?http://ad.cn.doubleclick.net/clk;4983632;7740969;c?http://www.ibm.com/cn/promotion/optin/reg.shtml">"IBM优惠价特权，谁先来谁先得！"</a>
William.Jiang wrote: > > hi,all hackers of postgres > > when postmaster start as a service . another two > processes(collector & buffer ) start their work at the same > time. > > I have read the code and I am wondering why we need two > processes to do the work. I think one process can work as > well. Are there something special you considered when you > developed this feature? One collects statistics for the pg_stat tables, and the other does checkpoints. They are different functions. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001+ If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania19073
"William.Jiang" <jiang_sir@yahoo.com.cn> writes:
> I have read the code and I am wondering why we need two processes to do the work. I think one process can work as
well.Are there something special you considered when you developed this feature?
It's a buffering issue. Read the discussion in the pghackers archives
for details.
regards, tom lane
<p>Sorry to say that I cannot see which process is used to do checkpoints. I just see two main functions. <p> pgstat_recvbuffer():this function is to receive the information from the postgres .this function is the main body ofbuffer process <p>pgstat_min():this function is to do the job of getting information from the buffer process and writingthem to the file . and this is the main body of collector process. <p>Any function else to do the checkpoint job?<p>Best Wishes! <p>William <p> <b><i>Bruce Momjian <pgman@candle.pha.pa.us></i></b> wrote:<blockquote style="BORDER-LEFT:#1010ff 2px solid; MARGIN-LEFT: 5px; PADDING-LEFT: 5px">William.Jiang wrote:<br />> <br />> hi,allhackers of postgres<br />> <br />> when postmaster start as a service . another two<br />> processes(collector& buffer ) start their work at the same<br />> time.<br />> <br />> I have read the codeand I am wondering why we need two<br />> processes to do the work. I think one process can work as<br />> well.Are there something special you considered when you<br />> developed this feature?<br /><br />One collects statisticsfor the pg_stat tables, and the other does<br />checkpoints. They are different functions.<br /><br />--<br />BruceMomjian | http://candle.pha.pa.us<br />pgman@candle.pha.pa.us | (610) 359-1001<br />+ If your life is a hard drive,| 13 Roberts Road<br />+ Christ can be your backup. | Newtown Square, Pennsylvania 19073</blockquote><p><br /><hr size="1"/><b>Do You Yahoo!?</b><br /><a href="http://rd.yahoo.com/mail_cn/tag/?http://ad.cn.doubleclick.net/clk;4983632;7740969;c?http://www.ibm.com/cn/promotion/optin/reg.shtml">"IBM优惠价特权，谁先来谁先得！"</a>