Re: [HACKERS] pageinspect and hash indexes

On Fri, Mar 24, 2017 at 9:21 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> On Thu, Mar 23, 2017 at 6:46 PM, Ashutosh Sharma <ashu.coek88@gmail.com> wrote:
>>>
>>> Oh, okay, but my main objection was that we should not check hash page
>>> type (hasho_flag) without ensuring whether it is a hash page.  Can you
>>> try to adjust the above code so that this check can be moved after
>>> hasho_page_id check?
>>
>> Yes, I got your point. I have done that but then i had to remove the
>> check for PageIsEmpty(). Anyways, I think PageIsEmpty() condition will
>> only be true for one page in entire hash index table and can be
>> ignored. If you wish, I could mention about it in the documentation.
>>
>
> Yeah, I think it is worth adding a Note in docs, but we can do that
> separately if required.
>
>>>
>>>> To avoid
>>>> this, at the start of verify_hash_page function itself if we recognise
>>>> page as UNUSED page we return immediately.
>>>>
>>>>>
>>>>> 2.
>>>>> + /* Check if it is an empty hash page. */
>>>>> + if (PageIsEmpty(page))
>>>>> + ereport(ERROR,
>>>>> + (errcode(ERRCODE_INDEX_CORRUPTED),
>>>>> + errmsg("index table contains empty page")));
>>>>>
>>>>>
>>>>> Do we want to give a separate message for EMPTY and NEW pages?  Isn't
>>>>> it better that the same error message can be given for both of them as
>>>>> from user perspective there is not much difference between both the
>>>>> messages?
>>>>
>>>> I think we should show separate message because they are two different
>>>> type of pages. In the sense like, one is initialised whereas other is
>>>> completely zero.
>>>>
>>>
>>> I understand your point, but not sure if it makes any difference to user.
>>>
>>
>> okay, I have now anyways removed the check for PageIsEmpty. Please
>> refer to the attached '0002
>> allow_pageinspect_handle_UNUSED_hash_pages.patch'
>>
>
> +
>         if (pageopaque->hasho_page_id != HASHO_PAGE_ID)
>                 ereport(ERROR,
>
> spurious white space.
>
>>
>> Also, I have attached
>> '0001-Mark-freed-overflow-page-as-UNUSED-pagetype-v2.patch' that
>> handles your comment mentioned in [1].
>>
>
> In general, we have to initialize prevblock with max_bucket, but here
> it is okay, because we anyway initialize it after this page is
> allocated as overflow page.
>
> Your patches look good to me except for small white space change.

Thanks for reviewing my patch. I have removed the extra white space.
Attached are both the patches.

--
With Regards,
Ashutosh Sharma
EnterpriseDB:http://www.enterprisedb.com

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