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From:Jorgen Loland Date:June 28 2011 6:55am
Subject:Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200
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On 06/27/2011 03:18 PM, Martin Hansson wrote:
> Øystein Grøvlen skrev 2011-06-16 12.18:
>> My question is not whether ordered access is required or not, but whether this
>> is the only case where select-> quick is set, but not used.
>>
> I'm sorry for the late answer. I'm also sorry to say I don't know. It's on my
> todo list to look this up, but I haven't gotten around to it yet.

The general rule in the code seems to be that if there is a quick, it will be 
used. Unfortunately there are at least a few exceptions. 
test_if_skip_sort_order() may e.g. destroy a previously created quick and 
replace it with either a new quick or ref access.

I think it works like this when we reach JOIN::exec():
* If JOIN_TAB->type == JT_ALL and select->quick is set, range access is used.
* If JOIN_TAB->type == JT_REF ref access is used even if select->quick is set

But the optimizer may reconsider many times before that.

-- 
Jørgen Løland | Senior Software Engineer | +47 73842138
Oracle MySQL
Trondheim, Norway
Thread
bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Roy Lyseng16 Jun
  • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Øystein Grøvlen16 Jun
    • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Roy Lyseng16 Jun
      • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Øystein Grøvlen16 Jun
        • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Roy Lyseng16 Jun
          • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Øystein Grøvlen16 Jun
  • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Øystein Grøvlen19 Jun
    • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Roy Lyseng21 Jun
  • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Jorgen Loland20 Jun
Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Roy Lyseng16 Jun
  • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Øystein Grøvlen16 Jun
    • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Martin Hansson27 Jun
      • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Jorgen Loland28 Jun
        • Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200Jorgen Loland28 Jun