Re: Parallel Bitmap Heap Scans segfaults due to (tbm->dsa==NULL) on PostgreSQL 10

On Thu, Oct 12, 2017 at 6:37 PM, Tomas Vondra
<tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>
>
> On 10/12/2017 02:40 PM, Dilip Kumar wrote:
>> On Thu, Oct 12, 2017 at 4:31 PM, Tomas Vondra
>> <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>>> Hi,
>>>
>>> It seems that Q19 from TPC-H is consistently failing with segfaults due
>>> to calling tbm_prepare_shared_iterate() with (tbm->dsa==NULL).
>>>
>>> I'm not very familiar with how the dsa is initialized and passed around,
>>> but I only see the failures when the bitmap is constructed by a mix of
>>> BitmapAnd and BitmapOr operations.
>>>
>> I think I have got the issue, bitmap_subplan_mark_shared is not
>> properly pushing the isshared flag to lower level bitmap index node,
>> and because of that tbm_create is passing NULL dsa while creating the
>> tidbitmap. So this problem will come in very specific combination of
>> BitmapOr and BitmapAnd when BitmapAnd is the first subplan for the
>> BitmapOr. If BitmapIndex is the first subplan under BitmapOr then
>> there is no problem because BitmapOr node will create the tbm by
>> itself and isshared is set for BitmapOr.
>>
>> Attached patch fixing the issue for me. I will thoroughly test this
>> patch with other scenario as well. Thanks for reporting.
>>
>
> Yep, this fixes the failures for me.
>
Thanks for confirming.

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com