Use PageIndexTupleOverwrite() within nbtree.
Use the PageIndexTupleOverwrite() bufpage.c routine within nbtree instead of deleting a tuple and re-inserting its replacement. This makes the intent of affected code slightly clearer. It also makes CREATE INDEX slightly faster, since there is no longer a need to shift every leaf page's line pointer array back and forth during index builds. Author: Peter Geoghegan, Anastasia Lubennikova Reviewed-By: Anastasia Lubennikova Discussion: https://postgr.es/m/CAH2-Wz=Zk=B9+Vwm376WuO7YTjFc2SSskifQm4Nme3RRRPtOSQ@mail.gmail.com
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@ -1653,8 +1653,7 @@ _bt_mark_page_halfdead(Relation rel, Buffer leafbuf, BTStack stack)
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opaque = (BTPageOpaque) PageGetSpecialPointer(page);
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opaque->btpo_flags |= BTP_HALF_DEAD;
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PageIndexTupleDelete(page, P_HIKEY);
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Assert(PageGetMaxOffsetNumber(page) == 0);
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Assert(PageGetMaxOffsetNumber(page) == P_HIKEY);
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MemSet(&trunctuple, 0, sizeof(IndexTupleData));
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trunctuple.t_info = sizeof(IndexTupleData);
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if (target != leafblkno)
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@ -1662,9 +1661,9 @@ _bt_mark_page_halfdead(Relation rel, Buffer leafbuf, BTStack stack)
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else
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BTreeTupleSetTopParent(&trunctuple, InvalidBlockNumber);
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if (PageAddItem(page, (Item) &trunctuple, sizeof(IndexTupleData), P_HIKEY,
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false, false) == InvalidOffsetNumber)
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elog(ERROR, "could not add dummy high key to half-dead page");
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if (!PageIndexTupleOverwrite(page, P_HIKEY, (Item) &trunctuple,
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IndexTupleSize(&trunctuple)))
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elog(ERROR, "could not overwrite high key in half-dead page");
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/* Must mark buffers dirty before XLogInsert */
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MarkBufferDirty(topparent);
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@ -943,7 +943,6 @@ _bt_buildadd(BTWriteState *wstate, BTPageState *state, IndexTuple itup)
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{
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IndexTuple lastleft;
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IndexTuple truncated;
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Size truncsz;
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/*
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* Truncate away any unneeded attributes from high key on leaf
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@ -961,26 +960,18 @@ _bt_buildadd(BTWriteState *wstate, BTPageState *state, IndexTuple itup)
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* choosing a split point here for a benefit that is bound to be
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* much smaller.
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*
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* Since the truncated tuple is often smaller than the original
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* tuple, it cannot just be copied in place (besides, we want to
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* actually save space on the leaf page). We delete the original
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* high key, and add our own truncated high key at the same
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* offset.
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*
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* Note that the page layout won't be changed very much. oitup is
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* already located at the physical beginning of tuple space, so we
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* only shift the line pointer array back and forth, and overwrite
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* the tuple space previously occupied by oitup. This is fairly
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* cheap.
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* Overwrite the old item with new truncated high key directly.
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* oitup is already located at the physical beginning of tuple
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* space, so this should directly reuse the existing tuple space.
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*/
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ii = PageGetItemId(opage, OffsetNumberPrev(last_off));
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lastleft = (IndexTuple) PageGetItem(opage, ii);
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truncated = _bt_truncate(wstate->index, lastleft, oitup,
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wstate->inskey);
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truncsz = IndexTupleSize(truncated);
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PageIndexTupleDelete(opage, P_HIKEY);
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_bt_sortaddtup(opage, truncsz, truncated, P_HIKEY);
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if (!PageIndexTupleOverwrite(opage, P_HIKEY, (Item) truncated,
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IndexTupleSize(truncated)))
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elog(ERROR, "failed to add high key to the index page");
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pfree(truncated);
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/* oitup should continue to point to the page's high key */
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