From a63250aa4645ff04f468160105da78ec0a69a3ea Mon Sep 17 00:00:00 2001 From: Peter Geoghegan Date: Mon, 13 May 2019 20:01:50 -0700 Subject: [PATCH] Overwrite lastright item with highkey in nbtsort.c. Using PageIndexTupleOverwrite() instead of deleting and re-inserting naively makes the code slightly simpler. It also saves us from having to shift every leaf page's line pointer array back and forth during index builds, which makes CREATE INDEX marginally faster. --- src/backend/access/nbtree/nbtsort.c | 21 ++++++--------------- 1 file changed, 6 insertions(+), 15 deletions(-) diff --git a/src/backend/access/nbtree/nbtsort.c b/src/backend/access/nbtree/nbtsort.c index d0b9013caf..0c93ba116b 100644 --- a/src/backend/access/nbtree/nbtsort.c +++ b/src/backend/access/nbtree/nbtsort.c @@ -943,7 +943,6 @@ _bt_buildadd(BTWriteState *wstate, BTPageState *state, IndexTuple itup) { IndexTuple lastleft; IndexTuple truncated; - Size truncsz; /* * Truncate away any unneeded attributes from high key on leaf @@ -961,26 +960,18 @@ _bt_buildadd(BTWriteState *wstate, BTPageState *state, IndexTuple itup) * choosing a split point here for a benefit that is bound to be * much smaller. * - * Since the truncated tuple is often smaller than the original - * tuple, it cannot just be copied in place (besides, we want to - * actually save space on the leaf page). We delete the original - * high key, and add our own truncated high key at the same - * offset. - * - * Note that the page layout won't be changed very much. oitup is - * already located at the physical beginning of tuple space, so we - * only shift the line pointer array back and forth, and overwrite - * the tuple space previously occupied by oitup. This is fairly - * cheap. + * Overwrite the old item with new truncated high key directly. + * oitup is already located at the physical beginning of tuple + * space, so this should directly reuse the existing tuple space. */ ii = PageGetItemId(opage, OffsetNumberPrev(last_off)); lastleft = (IndexTuple) PageGetItem(opage, ii); truncated = _bt_truncate(wstate->index, lastleft, oitup, wstate->inskey); - truncsz = IndexTupleSize(truncated); - PageIndexTupleDelete(opage, P_HIKEY); - _bt_sortaddtup(opage, truncsz, truncated, P_HIKEY); + if (!PageIndexTupleOverwrite(opage, P_HIKEY, (Item) truncated, + IndexTupleSize(truncated))) + elog(ERROR, "failed to add hikey to the index page"); pfree(truncated); /* oitup should continue to point to the page's high key */ -- 2.17.1