On Fri, Mar 24, 2017 at 9:21 AM, Amit Kapila <amit.kapil...@gmail.com> wrote: > On Thu, Mar 23, 2017 at 6:46 PM, Ashutosh Sharma <ashu.coe...@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
From 86eb711ea80b495c9d2f5228558682d0e95c41eb Mon Sep 17 00:00:00 2001 From: ashu <ashu@localhost.localdomain> Date: Thu, 23 Mar 2017 16:47:17 +0530 Subject: [PATCH] Mark freed overflow page as UNUSED pagetype v2 --- src/backend/access/hash/hash_xlog.c | 9 +++++++++ src/backend/access/hash/hashovfl.c | 13 ++++++++++++- 2 files changed, 21 insertions(+), 1 deletion(-) diff --git a/src/backend/access/hash/hash_xlog.c b/src/backend/access/hash/hash_xlog.c index d9ac42c..2ccaf46 100644 --- a/src/backend/access/hash/hash_xlog.c +++ b/src/backend/access/hash/hash_xlog.c @@ -697,11 +697,20 @@ hash_xlog_squeeze_page(XLogReaderState *record) if (XLogReadBufferForRedo(record, 2, &ovflbuf) == BLK_NEEDS_REDO) { Page ovflpage; + HashPageOpaque ovflopaque; ovflpage = BufferGetPage(ovflbuf); _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; + PageSetLSN(ovflpage, lsn); MarkBufferDirty(ovflbuf); } diff --git a/src/backend/access/hash/hashovfl.c b/src/backend/access/hash/hashovfl.c index a3cae21..d3eaee0 100644 --- a/src/backend/access/hash/hashovfl.c +++ b/src/backend/access/hash/hashovfl.c @@ -591,9 +591,20 @@ _hash_freeovflpage(Relation rel, Buffer bucketbuf, Buffer ovflbuf, /* * Initialize the freed overflow page. Just zeroing the page won't work, * because WAL replay routines expect pages to be initialized. See - * explanation of RBM_NORMAL mode atop XLogReadBufferExtended. + * explanation of RBM_NORMAL mode atop XLogReadBufferExtended. Also, mark + * the page as UNUSED type and retain it's page id. This allows the tools + * like pageinspect to consider it as a hash 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; + MarkBufferDirty(ovflbuf); if (BufferIsValid(prevbuf)) -- 1.8.3.1
diff --git a/contrib/pageinspect/hashfuncs.c b/contrib/pageinspect/hashfuncs.c index 812a03f..6ba8847 100644 --- a/contrib/pageinspect/hashfuncs.c +++ b/contrib/pageinspect/hashfuncs.c @@ -70,6 +70,7 @@ verify_hash_page(bytea *raw_page, int flags) errmsg("index table contains corrupted page"))); pageopaque = (HashPageOpaque) PageGetSpecialPointer(page); + if (pageopaque->hasho_page_id != HASHO_PAGE_ID) ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), @@ -77,6 +78,10 @@ verify_hash_page(bytea *raw_page, int flags) errdetail("Expected %08x, got %08x.", HASHO_PAGE_ID, pageopaque->hasho_page_id))); + /* Check if it is an unused hash page. */ + if (pageopaque->hasho_flag == LH_UNUSED_PAGE) + return page; + /* Check that page type is sane. */ pagetype = pageopaque->hasho_flag & LH_PAGE_TYPE; if (pagetype != LH_OVERFLOW_PAGE && pagetype != LH_BUCKET_PAGE &&
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