On Wed, Apr 18, 2018 at 10:47 PM, Teodor Sigaev <teo...@sigaev.ru> wrote: > Thank you, pushed.
Thanks. I saw another preexisting issue, this time one that has been around since 2007. Commit bc292937 forgot to remove a comment above _bt_insertonpg() (the 'afteritem' stuff ended up being moved to the bottom of _bt_findinsertloc(), where it remains today). The attached patch fixes this, and in passing mentions the fact that _bt_insertonpg() only performs retail insertions, and specifically never inserts high key items. I don't think it's necessary to add something about negative infinity items to the same comment block. While it's true that _bt_insertonpg() cannot truncate downlinks to make new minus infinity items, I see that as a narrower issue. -- Peter Geoghegan
From dced00be29775965a45c7889ca99e19b96d9e4d0 Mon Sep 17 00:00:00 2001 From: Peter Geoghegan <p...@bowt.ie> Date: Wed, 18 Apr 2018 22:38:32 -0700 Subject: [PATCH] Adjust _bt_insertonpg() comments. Remove an obsolete reference to the 'afteritem' argument, which was removed by commit bc292937. Add a comment that clarifies how _bt_insertonpg() indirectly handles the insertion of high key items. Author: Peter Geoghegan --- src/backend/access/nbtree/nbtinsert.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c index dbd5c92..ecf4e53 100644 --- a/src/backend/access/nbtree/nbtinsert.c +++ b/src/backend/access/nbtree/nbtinsert.c @@ -817,18 +817,18 @@ _bt_findinsertloc(Relation rel, * insertion, and the buffer must be pinned and write-locked. On return, * we will have dropped both the pin and the lock on the buffer. * - * When inserting to a non-leaf page, 'cbuf' is the left-sibling of the - * page we're inserting the downlink for. This function will clear the + * This routine only performs retail tuple insertions. 'itup' should + * always be either a non-highkey leaf item, or a downlink (new high + * key items are created indirectly, when a page is split). When + * inserting to a non-leaf page, 'cbuf' is the left-sibling of the page + * we're inserting the downlink for. This function will clear the * INCOMPLETE_SPLIT flag on it, and release the buffer. * * The locking interactions in this code are critical. You should * grok Lehman and Yao's paper before making any changes. In addition, * you need to understand how we disambiguate duplicate keys in this * implementation, in order to be able to find our location using - * L&Y "move right" operations. Since we may insert duplicate user - * keys, and since these dups may propagate up the tree, we use the - * 'afteritem' parameter to position ourselves correctly for the - * insertion on internal pages. + * L&Y "move right" operations. *---------- */ static void -- 2.7.4
