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From:Øystein Grøvlen Date:June 16 2011 9:37am
Subject:Re: bzr commit into mysql-trunk branch (roy.lyseng:3385) Bug#12603200
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On 16/06/2011 11:25, Roy Lyseng wrote:
> On 16.06.11 11.21, Øystein Grøvlen wrote:
>> On 16/06/2011 10:48, Roy Lyseng wrote:
>>> On 16.06.11 10.03, Øystein Grøvlen wrote:
>>>> On 15/06/2011 15:57, Roy Lyseng wrote:
>>>>> #At file:///home/rl136806/mysql/repo/mysql-work0/ based on
>>>>> revid:jorgen.loland@stripped
>>>>>
>>>>> 3385 Roy Lyseng 2011-06-15
>>>>> Bug#12603200: Assert in QUICK_INDEX_MERGE_SELECT::need_sorted_output
>>>>>
>>>>> The problematic query is semi-join transformed and a LooseScan
>>>>> strategy is selected. setup_semijoin_dups_elimination() inspects
>>>>> the provided quick select object and attempts to set it to require
>>>>> ordering of output rows. However, the quick select object was not
>>>>> selected in the first place (see
>>>>> Loose_scan_opt::check_ref_access_part1()), hence there is a missing
>>>>> check that the index covered by the quick select matches the index
>>>>> selected for the loose scan access.
>>>>>
>>>>> Fixed by adding this check, and also deleting the quick select
> object
>>>>> if it was not chosen for accessing this table.
>>>>
>>>> Hi,
>>>>
>>>> Did you consider deleting the quick select object at the point where
>>>> it is
>>>> decided to not use it?
>>>
>>> IMHO this is the place where the decision is taken. Do you have another
>>> view?
>>>
>>
>> You say in it the commit comments that the quick select object was not
>> selected
>> in Loose_scan_opt::check_ref_access_part1(). Sounds to me like that is
>> where the
>> decision is made. Maybe that is where the need_sorted_output call
>> should have
>> been put in the first place.
>
> Loose_scan_opt::check_ref_access_part1( is called from
> best_access_part() which explores potential uses of various access
> methods. The quick object might be used in a different context later, so
> it would be wrong to delete it at this stage.
> setup_semijoin_dups_elimination() is called from make_join_readinfo()
> which finalizes the plan after the optimal order has been chosen, so I
> think this is the right place to either select or discard the quick object.

That's a very good point. My next question is then whether loose_scan is 
the only case where the quick object may not be selected, or should it 
be deleted in other cases, too?

-- 
Øystein
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