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Reduce WAL activity for page splits:
> Currently, an index split writes all the data on the split page to > WAL. That's a lot of WAL traffic. The tuples that are copied to the > right page need to be WAL logged, but the tuples that stay on the > original page don't. Heikki Linnakangas
This commit is contained in:
Bruce Momjian
@ -8,7 +8,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.41 2007/02/01 19:10:25 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtxlog.c,v 1.42 2007/02/08 05:05:53 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -264,122 +264,165 @@ btree_xlog_split(bool onleft, bool isroot,
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{
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xl_btree_split *xlrec = (xl_btree_split *) XLogRecGetData(record);
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Relation reln;
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BlockNumber targetblk;
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OffsetNumber targetoff;
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BlockNumber leftsib;
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BlockNumber rightsib;
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BlockNumber downlink = 0;
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Buffer buffer;
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Page page;
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BTPageOpaque pageop;
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Buffer lbuf, rbuf;
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Page lpage, rpage;
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BTPageOpaque ropaque, lopaque;
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char *datapos;
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int datalen;
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bool bkp_left = record->xl_info & XLR_BKP_BLOCK_1;
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bool bkp_nextsib = record->xl_info & XLR_BKP_BLOCK_2;
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OffsetNumber newitemoff;
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Item newitem = NULL;
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Size newitemsz = 0;
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reln = XLogOpenRelation(xlrec->target.node);
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targetblk = ItemPointerGetBlockNumber(&(xlrec->target.tid));
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targetoff = ItemPointerGetOffsetNumber(&(xlrec->target.tid));
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leftsib = (onleft) ? targetblk : xlrec->otherblk;
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rightsib = (onleft) ? xlrec->otherblk : targetblk;
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reln = XLogOpenRelation(xlrec->node);
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/* Left (original) sibling */
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buffer = XLogReadBuffer(reln, leftsib, true);
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Assert(BufferIsValid(buffer));
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page = (Page) BufferGetPage(buffer);
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_bt_pageinit(page, BufferGetPageSize(buffer));
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pageop = (BTPageOpaque) PageGetSpecialPointer(page);
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pageop->btpo_prev = xlrec->leftblk;
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pageop->btpo_next = rightsib;
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pageop->btpo.level = xlrec->level;
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pageop->btpo_flags = (xlrec->level == 0) ? BTP_LEAF : 0;
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pageop->btpo_cycleid = 0;
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_bt_restore_page(page,
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(char *) xlrec + SizeOfBtreeSplit,
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xlrec->leftlen);
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if (onleft && xlrec->level > 0)
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{
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IndexTuple itup;
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/* extract downlink in the target tuple */
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itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, targetoff));
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downlink = ItemPointerGetBlockNumber(&(itup->t_tid));
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Assert(ItemPointerGetOffsetNumber(&(itup->t_tid)) == P_HIKEY);
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}
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PageSetLSN(page, lsn);
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PageSetTLI(page, ThisTimeLineID);
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MarkBufferDirty(buffer);
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UnlockReleaseBuffer(buffer);
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/* Right (new) sibling */
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buffer = XLogReadBuffer(reln, rightsib, true);
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Assert(BufferIsValid(buffer));
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page = (Page) BufferGetPage(buffer);
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_bt_pageinit(page, BufferGetPageSize(buffer));
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pageop = (BTPageOpaque) PageGetSpecialPointer(page);
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pageop->btpo_prev = leftsib;
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pageop->btpo_next = xlrec->rightblk;
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pageop->btpo.level = xlrec->level;
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pageop->btpo_flags = (xlrec->level == 0) ? BTP_LEAF : 0;
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pageop->btpo_cycleid = 0;
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_bt_restore_page(page,
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(char *) xlrec + SizeOfBtreeSplit + xlrec->leftlen,
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record->xl_len - SizeOfBtreeSplit - xlrec->leftlen);
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if (!onleft && xlrec->level > 0)
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{
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IndexTuple itup;
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/* extract downlink in the target tuple */
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itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, targetoff));
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downlink = ItemPointerGetBlockNumber(&(itup->t_tid));
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Assert(ItemPointerGetOffsetNumber(&(itup->t_tid)) == P_HIKEY);
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}
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PageSetLSN(page, lsn);
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PageSetTLI(page, ThisTimeLineID);
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MarkBufferDirty(buffer);
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UnlockReleaseBuffer(buffer);
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/* Fix left-link of right (next) page */
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if (!(record->xl_info & XLR_BKP_BLOCK_1))
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{
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if (xlrec->rightblk != P_NONE)
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{
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buffer = XLogReadBuffer(reln, xlrec->rightblk, false);
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if (BufferIsValid(buffer))
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{
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page = (Page) BufferGetPage(buffer);
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if (XLByteLE(lsn, PageGetLSN(page)))
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{
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UnlockReleaseBuffer(buffer);
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}
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else
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{
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pageop = (BTPageOpaque) PageGetSpecialPointer(page);
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pageop->btpo_prev = rightsib;
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PageSetLSN(page, lsn);
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PageSetTLI(page, ThisTimeLineID);
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MarkBufferDirty(buffer);
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UnlockReleaseBuffer(buffer);
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}
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}
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}
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}
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datapos = (char *) xlrec + SizeOfBtreeSplit;
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datalen = record->xl_len - SizeOfBtreeSplit;
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/* Forget any split this insertion completes */
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if (xlrec->level > 0)
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forget_matching_split(xlrec->target.node, downlink, false);
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{
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BlockNumber downlink = BlockIdGetBlockNumber((BlockId) datapos);
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datapos += sizeof(BlockIdData);
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datalen -= sizeof(BlockIdData);
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forget_matching_split(xlrec->node, downlink, false);
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}
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/* Extract newitem and newitemoff */
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if (!bkp_left && onleft)
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{
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IndexTupleData itupdata;
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/* Extract the offset of the new tuple and it's contents */
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memcpy(&newitemoff, datapos, sizeof(OffsetNumber));
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datapos += sizeof(OffsetNumber);
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datalen -= sizeof(OffsetNumber);
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newitem = datapos;
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/* Need to copy tuple header due to alignment considerations */
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memcpy(&itupdata, datapos, sizeof(IndexTupleData));
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newitemsz = IndexTupleDSize(itupdata);
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newitemsz = MAXALIGN(newitemsz);
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datapos += newitemsz;
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datalen -= newitemsz;
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}
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/* Reconstruct right (new) sibling */
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rbuf = XLogReadBuffer(reln, xlrec->rightsib, true);
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Assert(BufferIsValid(rbuf));
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rpage = (Page) BufferGetPage(rbuf);
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_bt_pageinit(rpage, BufferGetPageSize(rbuf));
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ropaque = (BTPageOpaque) PageGetSpecialPointer(rpage);
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ropaque->btpo_prev = xlrec->leftsib;
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ropaque->btpo_next = xlrec->rnext;
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ropaque->btpo.level = xlrec->level;
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ropaque->btpo_flags = (xlrec->level == 0) ? BTP_LEAF : 0;
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ropaque->btpo_cycleid = 0;
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_bt_restore_page(rpage, datapos, datalen);
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PageSetLSN(rpage, lsn);
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PageSetTLI(rpage, ThisTimeLineID);
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MarkBufferDirty(rbuf);
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/* don't release the buffer yet, because reconstructing the left sibling
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* needs to access the data on the right page
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*/
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/* Reconstruct left (original) sibling */
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if(!bkp_left)
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{
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lbuf = XLogReadBuffer(reln, xlrec->leftsib, false);
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if (BufferIsValid(lbuf))
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{
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lpage = (Page) BufferGetPage(lbuf);
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lopaque = (BTPageOpaque) PageGetSpecialPointer(lpage);
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if (!XLByteLE(lsn, PageGetLSN(lpage)))
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{
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/* Remove the items from the left page that were copied to
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* right page, and add the new item if it was inserted to
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* left page.
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*/
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OffsetNumber off;
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OffsetNumber maxoff = PageGetMaxOffsetNumber(lpage);
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ItemId hiItemId;
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Item hiItem;
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for(off = maxoff ; off >= xlrec->firstright; off--)
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PageIndexTupleDelete(lpage, off);
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if (onleft)
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{
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if (PageAddItem(lpage, newitem, newitemsz, newitemoff,
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LP_USED) == InvalidOffsetNumber)
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elog(PANIC, "can't add new item to left sibling after split");
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}
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/* Set high key equal to the first key on the right page */
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hiItemId = PageGetItemId(rpage, P_FIRSTDATAKEY(ropaque));
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hiItem = PageGetItem(rpage, hiItemId);
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if(!P_RIGHTMOST(lopaque))
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{
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/* but remove the old high key first */
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PageIndexTupleDelete(lpage, P_HIKEY);
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}
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if(PageAddItem(lpage, hiItem, ItemIdGetLength(hiItemId),
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P_HIKEY, LP_USED) == InvalidOffsetNumber)
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elog(PANIC, "can't add high key after split to left page");
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/* Fix opaque fields */
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lopaque->btpo_flags = (xlrec->level == 0) ? BTP_LEAF : 0;
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lopaque->btpo_next = xlrec->rightsib;
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lopaque->btpo_cycleid = 0;
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PageSetLSN(lpage, lsn);
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PageSetTLI(lpage, ThisTimeLineID);
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MarkBufferDirty(lbuf);
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}
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UnlockReleaseBuffer(lbuf);
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}
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}
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/* we no longer need the right buffer. */
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UnlockReleaseBuffer(rbuf);
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/* Fix left-link of the page to the right of the new right sibling */
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if (!bkp_nextsib && xlrec->rnext != P_NONE)
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{
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Buffer buffer = XLogReadBuffer(reln, xlrec->rnext, false);
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if (BufferIsValid(buffer))
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{
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Page page = (Page) BufferGetPage(buffer);
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if (!XLByteLE(lsn, PageGetLSN(page)))
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{
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BTPageOpaque pageop = (BTPageOpaque) PageGetSpecialPointer(page);
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pageop->btpo_prev = xlrec->rightsib;
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PageSetLSN(page, lsn);
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PageSetTLI(page, ThisTimeLineID);
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MarkBufferDirty(buffer);
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}
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UnlockReleaseBuffer(buffer);
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}
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}
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/* The job ain't done till the parent link is inserted... */
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log_incomplete_split(xlrec->target.node,
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leftsib, rightsib, isroot);
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log_incomplete_split(xlrec->node,
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xlrec->leftsib, xlrec->rightsib, isroot);
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}
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static void
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@ -727,40 +770,48 @@ btree_desc(StringInfo buf, uint8 xl_info, char *rec)
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{
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xl_btree_split *xlrec = (xl_btree_split *) rec;
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appendStringInfo(buf, "split_l: ");
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out_target(buf, &(xlrec->target));
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appendStringInfo(buf, "; oth %u; rgh %u",
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xlrec->otherblk, xlrec->rightblk);
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appendStringInfo(buf, "split_l: rel %u/%u/%u ",
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xlrec->node.spcNode, xlrec->node.dbNode,
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xlrec->node.relNode);
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appendStringInfo(buf, "left %u, right %u off %u level %u",
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xlrec->leftsib, xlrec->rightsib,
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xlrec->firstright, xlrec->level);
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break;
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}
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case XLOG_BTREE_SPLIT_R:
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{
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xl_btree_split *xlrec = (xl_btree_split *) rec;
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appendStringInfo(buf, "split_r: ");
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out_target(buf, &(xlrec->target));
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appendStringInfo(buf, "; oth %u; rgh %u",
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xlrec->otherblk, xlrec->rightblk);
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appendStringInfo(buf, "split_r: rel %u/%u/%u ",
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xlrec->node.spcNode, xlrec->node.dbNode,
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xlrec->node.relNode);
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appendStringInfo(buf, "left %u, right %u off %u level %u",
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xlrec->leftsib, xlrec->rightsib,
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xlrec->firstright, xlrec->level);
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break;
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}
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case XLOG_BTREE_SPLIT_L_ROOT:
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{
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xl_btree_split *xlrec = (xl_btree_split *) rec;
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appendStringInfo(buf, "split_l_root: ");
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out_target(buf, &(xlrec->target));
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appendStringInfo(buf, "; oth %u; rgh %u",
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xlrec->otherblk, xlrec->rightblk);
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appendStringInfo(buf, "split_l_root: rel %u/%u/%u ",
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xlrec->node.spcNode, xlrec->node.dbNode,
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xlrec->node.relNode);
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appendStringInfo(buf, "left %u, right %u off %u level %u",
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xlrec->leftsib, xlrec->rightsib,
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xlrec->firstright, xlrec->level);
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break;
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}
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case XLOG_BTREE_SPLIT_R_ROOT:
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{
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xl_btree_split *xlrec = (xl_btree_split *) rec;
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appendStringInfo(buf, "split_r_root: ");
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out_target(buf, &(xlrec->target));
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appendStringInfo(buf, "; oth %u; rgh %u",
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xlrec->otherblk, xlrec->rightblk);
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appendStringInfo(buf, "split_r_root: rel %u/%u/%u ",
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xlrec->node.spcNode, xlrec->node.dbNode,
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xlrec->node.relNode);
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appendStringInfo(buf, "left %u, right %u off %u level %u",
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xlrec->leftsib, xlrec->rightsib,
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xlrec->firstright, xlrec->level);
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break;
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}
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case XLOG_BTREE_DELETE:
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