Horton

Re: Corrupted btree index on HEAD because of covering indexes

Teodor Sigaev <teodor@sigaev.ru>

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From: Teodor Sigaev <teodor@sigaev.ru>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Michael Paquier <michael@paquier.xyz>, Postgres hackers <pgsql-hackers@postgresql.org>, Anastasia Lubennikova <a.lubennikova@postgrespro.ru>
Date: 2018-04-19T16:42:59Z
Lists: pgsql-hackers

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> I'll take a look tomorrow.

Interesting, contrib/amcheck doesn't find any error in index. Seems, it's 
subject for further improvement.

Nevertheless, seems, I found. In _bt_mark_page_halfdead() we use truncated high 
key IndexTuple as a storage of blocknumber of top parent to remove. And sets 
BTreeTupleSetNAtts(&trunctuple, 0) - it's stored in ip_posid.

But some later, in _bt_unlink_halfdead_page() we check ItemPointer high key with 
ItemPointerIsValid macro - and it returns false, because offset is actually 
InvalidOffsetNumber - i.e. 0 which was set by BTreeTupleSetNAtts. And some wrong 
decisions are follows, I didn't look at that.

Trivial and naive fix is attached, but for me it looks a bit annoing that we 
store pointer (leafhikey) somewhere inside unlocked page.



-- 
Teodor Sigaev                                   E-mail: teodor@sigaev.ru
                                                    WWW: http://www.sigaev.ru/

Commits

  1. Add missing and dangling downlink checks to amcheck

  2. Fix wrong validation of top-parent pointer during page deletion in Btree.

  3. Add integrity-checking functions to pg_visibility.

  4. Make the handling of interrupted B-tree page splits more robust.