>> I think it is not just happening for freed overflow but also for newly
>> allocated bucket page. It would be good if we could mark freed
>> overflow page as UNUSED page rather than just initialising it's header
>> portion and leaving the page type in special area as it is. Attached
>> is the patch '0001-mark_freed_ovflpage_as_UNUSED_pagetype.patch' that
>> marks a freed overflow page as an unused page.
>>
>
> _hash_pageinit(ovflpage, BufferGetPageSize(ovflbuf));
> +
> + ovflopaque = (HashPageOpaque) PageGetSpecialPointer(ovflpage);
> +
> + ovflopaque->hasho_prevblkno = InvalidBlockNumber;
> + ovflopaque->hasho_nextblkno = InvalidBlockNumber;
> + ovflopaque->hasho_bucket = -1;
> + ovflopaque->hasho_flag = LH_UNUSED_PAGE;
> + ovflopaque->hasho_page_id = HASHO_PAGE_ID;
> +
>
> You need similar initialization in replay routine as well.
I will do that and share the patch shortly. Thanks.
>
>> Also, I have now changed pageinspect module to handle unused and empty
>> hash index page. Attached is the patch
>> (0002-allow_pageinspect_handle_UNUSED_OR_EMPTY_hash_pages.patch) for
>> the same.
>>
>
> 1.
> @@ -70,6 +70,17 @@ verify_hash_page(bytea *raw_page, int flags)
> pageopaque = (HashPageOpaque) PageGetSpecialPointer(page);
> +
> + /* Check if it is an unused hash page. */
> + if (pageopaque->hasho_flag == LH_UNUSED_PAGE)
> + return page;
>
>
> I don't see we need to have a separate check for unused page, why
> can't it be checked with other page types in below check.
>
> if (pagetype != LH_OVERFLOW_PAGE && pagetype != LH_BUCKET_PAGE &&
> pagetype != LH_BITMAP_PAGE && pagetype != LH_META_PAGE)
That is because UNUSED page is as good as an empty page except that
empty page doesn't have any pagetype. If we add condition for checking
UNUSED page in above if check it will never show unused page as an
unsed page rather it will always show it as an empty page. 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.
--
With Regards,
Ashutosh Sharma
EnterpriseDB:http://www.enterprisedb.com
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