Re: BUG #17245: Index corruption involving deduplicated entries

During investigation, `SELECT
bt_index_parent_check('mediawiki.page_main_title', true, true);`
displayed no errors.

I have installed the same build of 14.0 in a VM and started it with the
data directory before reindex. pg_amcheck does report errors, but these
are not related to the index in question (page_main_title):

$ ./pg_amcheck -U postgres --heapallindexed --parent-check --rootdescend
azurlane_wiki
btree index "azurlane_wiki.mediawiki.page_redirect_namespace_len":
    ERROR:  posting list contains misplaced TID in index
"page_redirect_namespace_len"
    DETAIL:  Index tid=(14,9) posting list offset=110 page lsn=2/2C4F7CD8.
btree index "azurlane_wiki.mediawiki.page_len":
    ERROR:  posting list contains misplaced TID in index "page_len"
    DETAIL:  Index tid=(1,2) posting list offset=34 page lsn=2/2DDA2378.
btree index "azurlane_wiki.mediawiki.transcode_key_idx":
    ERROR:  posting list contains misplaced TID in index
"transcode_key_idx"
    DETAIL:  Index tid=(1,9) posting list offset=5 page lsn=2/2B53AED8.

This instance displays the same behaviour with page_main_title:

azurlane_wiki=# select ctid, page_title from mediawiki.page WHERE
page_title = 'Isokaze' and page_namespace = 0;
   ctid   | page_title
----------+------------
 (181,53) | Ying_Swei
 (722,3)  | Isokaze
(2 rows)

azurlane_wiki=# select ctid, page_title from mediawiki.page WHERE
page_title = 'Kaga' and page_namespace = 0;
   ctid   | page_title
----------+------------
 (446,32) | Belfast
 (720,53) | Kaga

(2 rows)

After REINDEX'ing the three indices listed by pg_amcheck, there is no
apparent change to the state of the page_main_title index:

azurlane_wiki=# reindex index mediawiki.page_redirect_namespace_len;
REINDEX
azurlane_wiki=# reindex index mediawiki.page_len;
REINDEX
azurlane_wiki=# reindex index mediawiki.transcode_key_idx;
REINDEX

[xiatian(at)freebsd pg_amcheck]$ ./pg_amcheck -U postgres --heapallindexed
--parent-check --rootdescend azurlane_wiki
[xiatian(at)freebsd pg_amcheck]$

azurlane_wiki=# select ctid, page_title from mediawiki.page WHERE
page_title = 'Kaga' and page_namespace = 0;
   ctid   | page_title
----------+------------
 (446,32) | Belfast
 (720,53) | Kaga
(2 rows)

P. S. My previous copy of this e-mail was sent from an invalid address;
I apologise for the possible noise.

--
K. R.