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Correct obsolete nbtsort.c minimum key comment. 

It is no longer possible under any circumstances for nbtree code to
reconstruct a strict lower bound key (parent page's pivot tuple key) for
a right sibling page by retrieving the first item in the right sibling
page.
This commit is contained in:
Peter Geoghegan 2019-05-07 21:42:12 -07:00
parent e5f9786317
commit d65b5ccad6
1 changed files with 4 additions and 6 deletions
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10
src/backend/access/nbtree/nbtsort.c
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@ -1007,9 +1007,8 @@ _bt_buildadd(BTWriteState *wstate, BTPageState *state, IndexTuple itup)
pfree(state->btps_minkey); pfree(state->btps_minkey);
/* /*
* Save a copy of the minimum key for the new page. We have to copy * Save a copy of the high key from the old page. It is also used as
* it off the old page, not the new one, in case we are not at leaf * the minimum key for the new page.
* level.
*/ */
state->btps_minkey = CopyIndexTuple(oitup); state->btps_minkey = CopyIndexTuple(oitup);
@ -1045,9 +1044,8 @@ _bt_buildadd(BTWriteState *wstate, BTPageState *state, IndexTuple itup)
* If the new item is the first for its page, stash a copy for later. Note * If the new item is the first for its page, stash a copy for later. Note
* this will only happen for the first item on a level; on later pages, * this will only happen for the first item on a level; on later pages,
* the first item for a page is copied from the prior page in the code * the first item for a page is copied from the prior page in the code
* above. Since the minimum key for an entire level is only used as a * above. The minimum key for an entire level is nothing more than a
* minus infinity downlink, and never as a high key, there is no need to * minus infinity (downlink only) pivot tuple placeholder.
* truncate away suffix attributes at this point.
*/ */
if (last_off == P_HIKEY) if (last_off == P_HIKEY)
{ {