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From:Karen Abgarian Date:May 8 2012 6:51pm
Subject:Re: 回复: 回复
: 回复: Why is creating
indexes faster after inserting massive data rows?
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Hi, 

If MyISAM tables were being written directly to disk, the MyISAM tables would be so slow
that nobody would ever use them.    That's the cornerstone of their performance, that the
writes do not wait for the physical I/O to complete!



On May 8, 2012, at 3:07 AM, Johan De Meersman wrote:

> ----- Original Message -----
>> From: "Zhangzhigang" <zzgang_2008@stripped>
>> 
>> As i known, the mysql writes the data to disk directly but does not
>> use the Os cache when the table is updating.
> 
> If it were to use the OS cache for reading but not writing, then the OS cache would
> be inconsistent with the underlying filesystem as soon as you wrote a block, and you'd
> need some complicated logic to figure out which of the two was correct.
> 
> No, the MyISAM engine will simply yield to whatever the kernel/VFS wants to do with
> the blocks; whereas InnoDB explicitly opens the files with O_SYNC and bypasses the OS
> cache entirely, because it manages it's own buffer cache.
> 
>> If it writes to the Os cache, which leads to massive system invoking,
>> when the table is inserted a lot of rows one by one.
> 
> From the code's point of view, you simply request a read or a write. Wether or not
> the OS cache gets in between is entirely a matter for the kernel to decide, assuming you
> specified no specific options at file open time.
> 
> 
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Thread
Why is creating indexes faster after inserting massive data rows?Zhangzhigang7 May
  • Re: Why is creating indexes faster after inserting massive data rows?Ananda Kumar7 May
    • 回复: Why is creating indexes faster after inserting massive data rows?Zhangzhigang7 May
  • Re: Why is creating indexes faster after inserting massive data rows?Johan De Meersman7 May
    • 回复: Why is creating indexes faster after inserting massive data rows?Zhangzhigang7 May
      • Re: 回复: Why is creating indexes faster after inserting massive data rows?Alex Schaft7 May
        • 回复: 回复: Why is creating indexes faster after inserting massive data rows?Zhangzhigang7 May
          • Re: 回复: 回复: Why is creating indexes faster after inserting massive data rows?Claudio Nanni7 May
            • too nice not to share it!hsv2 Oct
          • Re: 回复: 回复: Why is creating indexes faster after inserting massive data rows?Mihamina Rakotomandimby30 May
      • Re: 回复: Why is creating indexes faster after inserting massive data rows?Claudio Nanni7 May
        • 回复: 回复: Why is creating indexes faster after inserting massive data rows?Zhangzhigang7 May
      • Re: 回复: Why is creating indexes faster after inserting massive data rows?Johan De Meersman7 May
        • RE: 回复: Why is creating indexes faster after inserting massive data rows?Rick James7 May
        • Re: 回复: Why is creating indexes faster after inserting massive data rows?Karen Abgarian7 May
          • 回复: 回复: Why is creating indexes faster after inserting massive data rows?Zhangzhigang8 May
            • Re: 回复: 回复: Why is creating indexes faster after inserting massive data rows?Karen Abgarian8 May
              • 回复: 回复: 回复: Why is creating indexes faster after inserting massive data rows?Zhangzhigang8 May
                • Re: 回复: 回复: 回复: Why is creating indexes faster after inserting massive data rows?Johan De Meersman8 May
                  • 回复: 回复: 回复: 回复: Why is creating indexes faster after inserting massive data rows?Zhangzhigang8 May
                  • Re: 回复: 回复: 回复: Why is creating indexes faster after inserting massive data rows?Karen Abgarian8 May
                    • 回复: 回复: 回复: 回复: Why is creating indexes faster after inserting massive data rows?Zhangzhigang9 May
              • RE: 回复: 回复: Why is creating indexes faster after inserting massive data rows?Rick James10 May
            • Re: 回复: 回复: Why is creating indexes faster after inserting massive data rows?Johan De Meersman8 May
        • Re: 回复: Why is creating indexes faster after inserting massive data rows?Karen Abgarian7 May
    • RE: Why is creating indexes faster after inserting massive datarows?Rick James7 May
      • 回复: Why is creating indexes faster after inserting massive data rows?Zhangzhigang9 May
        • RE: 回复: Why is creating indexes faster after inserting massive data rows?Rick James9 May
          • Re: 回复: Why is creating indexes faster after inserting massive data rows?Claudio Nanni9 May
          • 回复: 回复: Why is creating indexes faster after inserting massive data rows?Zhangzhigang10 May