/* * _bt_initmetapage() -- Fill a page buffer with a correct metapage image */ void _bt_initmetapage(Page page, BlockNumber rootbknum, uint32 level) { BTMetaPageData *metad; BTPageOpaque metaopaque; _bt_pageinit(page, BLCKSZ); metad = BTPageGetMeta(page); metad->btm_magic = BTREE_MAGIC; metad->btm_version = BTREE_VERSION; metad->btm_root = rootbknum; metad->btm_level = level; metad->btm_fastroot = rootbknum; metad->btm_fastlevel = level; metaopaque = (BTPageOpaque) PageGetSpecialPointer(page); metaopaque->btpo_flags = BTP_META; /* * Set pd_lower just past the end of the metadata. This is not essential * but it makes the page look compressible to xlog.c. */ ((PageHeader) page)->pd_lower = ((char *) metad + sizeof(BTMetaPageData)) - (char *) page; }
static void _bt_restore_meta(XLogReaderState *record, uint8 block_id) { XLogRecPtr lsn = record->EndRecPtr; Buffer metabuf; Page metapg; BTMetaPageData *md; BTPageOpaque pageop; xl_btree_metadata *xlrec; char *ptr; Size len; metabuf = XLogInitBufferForRedo(record, block_id); ptr = XLogRecGetBlockData(record, block_id, &len); Assert(len == sizeof(xl_btree_metadata)); Assert(BufferGetBlockNumber(metabuf) == BTREE_METAPAGE); xlrec = (xl_btree_metadata *) ptr; metapg = BufferGetPage(metabuf); _bt_pageinit(metapg, BufferGetPageSize(metabuf)); md = BTPageGetMeta(metapg); md->btm_magic = BTREE_MAGIC; md->btm_version = BTREE_VERSION; md->btm_root = xlrec->root; md->btm_level = xlrec->level; md->btm_fastroot = xlrec->fastroot; md->btm_fastlevel = xlrec->fastlevel; pageop = (BTPageOpaque) PageGetSpecialPointer(metapg); pageop->btpo_flags = BTP_META; /* * Set pd_lower just past the end of the metadata. This is not essential * but it makes the page look compressible to xlog.c. */ ((PageHeader) metapg)->pd_lower = ((char *) md + sizeof(BTMetaPageData)) - (char *) metapg; PageSetLSN(metapg, lsn); MarkBufferDirty(metabuf); UnlockReleaseBuffer(metabuf); }
static void btree_xlog_newroot(XLogReaderState *record) { XLogRecPtr lsn = record->EndRecPtr; xl_btree_newroot *xlrec = (xl_btree_newroot *) XLogRecGetData(record); Buffer buffer; Page page; BTPageOpaque pageop; char *ptr; Size len; buffer = XLogInitBufferForRedo(record, 0); page = (Page) BufferGetPage(buffer); _bt_pageinit(page, BufferGetPageSize(buffer)); pageop = (BTPageOpaque) PageGetSpecialPointer(page); pageop->btpo_flags = BTP_ROOT; pageop->btpo_prev = pageop->btpo_next = P_NONE; pageop->btpo.level = xlrec->level; if (xlrec->level == 0) pageop->btpo_flags |= BTP_LEAF; pageop->btpo_cycleid = 0; if (xlrec->level > 0) { ptr = XLogRecGetBlockData(record, 0, &len); _bt_restore_page(page, ptr, len); /* Clear the incomplete-split flag in left child */ _bt_clear_incomplete_split(record, 1); } PageSetLSN(page, lsn); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); _bt_restore_meta(record, 2); }
/* * allocate workspace for a new, clean btree page, not linked to any siblings. */ static Page _bt_blnewpage(uint32 level) { Page page; BTPageOpaque opaque; page = (Page) palloc(BLCKSZ); /* Zero the page and set up standard page header info */ _bt_pageinit(page, BLCKSZ); /* Initialize BT opaque state */ opaque = (BTPageOpaque) PageGetSpecialPointer(page); opaque->btpo_prev = opaque->btpo_next = P_NONE; opaque->btpo.level = level; opaque->btpo_flags = (level > 0) ? 0 : BTP_LEAF; opaque->btpo_cycleid = 0; /* Make the P_HIKEY line pointer appear allocated */ ((PageHeader) page)->pd_lower += sizeof(ItemIdData); return page; }
/* * _bt_getbuf() -- Get a buffer by block number for read or write. * * blkno == P_NEW means to get an unallocated index page. The page * will be initialized before returning it. * * When this routine returns, the appropriate lock is set on the * requested buffer and its reference count has been incremented * (ie, the buffer is "locked and pinned"). Also, we apply * _bt_checkpage to sanity-check the page (except in P_NEW case). */ Buffer _bt_getbuf(Relation rel, BlockNumber blkno, int access) { Buffer buf; MIRROREDLOCK_BUFMGR_MUST_ALREADY_BE_HELD; if (blkno != P_NEW) { /* Read an existing block of the relation */ buf = ReadBuffer(rel, blkno); LockBuffer(buf, access); _bt_checkpage(rel, buf); } else { bool needLock; Page page; Assert(access == BT_WRITE); /* * First see if the FSM knows of any free pages. * * We can't trust the FSM's report unreservedly; we have to check that * the page is still free. (For example, an already-free page could * have been re-used between the time the last VACUUM scanned it and * the time the VACUUM made its FSM updates.) * * In fact, it's worse than that: we can't even assume that it's safe * to take a lock on the reported page. If somebody else has a lock * on it, or even worse our own caller does, we could deadlock. (The * own-caller scenario is actually not improbable. Consider an index * on a serial or timestamp column. Nearly all splits will be at the * rightmost page, so it's entirely likely that _bt_split will call us * while holding a lock on the page most recently acquired from FSM. A * VACUUM running concurrently with the previous split could well have * placed that page back in FSM.) * * To get around that, we ask for only a conditional lock on the * reported page. If we fail, then someone else is using the page, * and we may reasonably assume it's not free. (If we happen to be * wrong, the worst consequence is the page will be lost to use till * the next VACUUM, which is no big problem.) */ for (;;) { blkno = GetFreeIndexPage(&rel->rd_node); if (blkno == InvalidBlockNumber) break; buf = ReadBuffer(rel, blkno); if (ConditionalLockBuffer(buf)) { page = BufferGetPage(buf); if (_bt_page_recyclable(page)) { /* Okay to use page. Re-initialize and return it */ _bt_pageinit(page, BufferGetPageSize(buf)); return buf; } elog(DEBUG2, "FSM returned nonrecyclable page"); _bt_relbuf(rel, buf); } else { elog(DEBUG2, "FSM returned nonlockable page"); /* couldn't get lock, so just drop pin */ ReleaseBuffer(buf); } } /* * Extend the relation by one page. * * We have to use a lock to ensure no one else is extending the rel at * the same time, else we will both try to initialize the same new * page. We can skip locking for new or temp relations, however, * since no one else could be accessing them. */ needLock = !RELATION_IS_LOCAL(rel); if (needLock) LockRelationForExtension(rel, ExclusiveLock); buf = ReadBuffer(rel, P_NEW); /* Acquire buffer lock on new page */ LockBuffer(buf, BT_WRITE); /* * Release the file-extension lock; it's now OK for someone else to * extend the relation some more. Note that we cannot release this * lock before we have buffer lock on the new page, or we risk a race * condition against btvacuumscan --- see comments therein. */ if (needLock) UnlockRelationForExtension(rel, ExclusiveLock); /* Initialize the new page before returning it */ page = BufferGetPage(buf); Assert(PageIsNew((PageHeader) page)); _bt_pageinit(page, BufferGetPageSize(buf)); } /* ref count and lock type are correct */ return buf; }
static void btree_xlog_unlink_page(uint8 info, XLogReaderState *record) { XLogRecPtr lsn = record->EndRecPtr; xl_btree_unlink_page *xlrec = (xl_btree_unlink_page *) XLogRecGetData(record); BlockNumber leftsib; BlockNumber rightsib; Buffer buffer; Page page; BTPageOpaque pageop; leftsib = xlrec->leftsib; rightsib = xlrec->rightsib; /* * In normal operation, we would lock all the pages this WAL record * touches before changing any of them. In WAL replay, it should be okay * to lock just one page at a time, since no concurrent index updates can * be happening, and readers should not care whether they arrive at the * target page or not (since it's surely empty). */ /* Fix left-link of right sibling */ if (XLogReadBufferForRedo(record, 2, &buffer) == BLK_NEEDS_REDO) { page = (Page) BufferGetPage(buffer); pageop = (BTPageOpaque) PageGetSpecialPointer(page); pageop->btpo_prev = leftsib; PageSetLSN(page, lsn); MarkBufferDirty(buffer); } if (BufferIsValid(buffer)) UnlockReleaseBuffer(buffer); /* Fix right-link of left sibling, if any */ if (leftsib != P_NONE) { if (XLogReadBufferForRedo(record, 1, &buffer) == BLK_NEEDS_REDO) { page = (Page) BufferGetPage(buffer); pageop = (BTPageOpaque) PageGetSpecialPointer(page); pageop->btpo_next = rightsib; PageSetLSN(page, lsn); MarkBufferDirty(buffer); } if (BufferIsValid(buffer)) UnlockReleaseBuffer(buffer); } /* Rewrite target page as empty deleted page */ buffer = XLogInitBufferForRedo(record, 0); page = (Page) BufferGetPage(buffer); _bt_pageinit(page, BufferGetPageSize(buffer)); pageop = (BTPageOpaque) PageGetSpecialPointer(page); pageop->btpo_prev = leftsib; pageop->btpo_next = rightsib; pageop->btpo.xact = xlrec->btpo_xact; pageop->btpo_flags = BTP_DELETED; pageop->btpo_cycleid = 0; PageSetLSN(page, lsn); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); /* * If we deleted a parent of the targeted leaf page, instead of the leaf * itself, update the leaf to point to the next remaining child in the * branch. */ if (XLogRecHasBlockRef(record, 3)) { /* * There is no real data on the page, so we just re-create it from * scratch using the information from the WAL record. */ IndexTupleData trunctuple; buffer = XLogInitBufferForRedo(record, 3); page = (Page) BufferGetPage(buffer); pageop = (BTPageOpaque) PageGetSpecialPointer(page); _bt_pageinit(page, BufferGetPageSize(buffer)); pageop->btpo_flags = BTP_HALF_DEAD | BTP_LEAF; pageop->btpo_prev = xlrec->leafleftsib; pageop->btpo_next = xlrec->leafrightsib; pageop->btpo.level = 0; pageop->btpo_cycleid = 0; /* Add a dummy hikey item */ MemSet(&trunctuple, 0, sizeof(IndexTupleData)); trunctuple.t_info = sizeof(IndexTupleData); if (xlrec->topparent != InvalidBlockNumber) ItemPointerSet(&trunctuple.t_tid, xlrec->topparent, P_HIKEY); else ItemPointerSetInvalid(&trunctuple.t_tid); if (PageAddItem(page, (Item) &trunctuple, sizeof(IndexTupleData), P_HIKEY, false, false) == InvalidOffsetNumber) elog(ERROR, "could not add dummy high key to half-dead page"); PageSetLSN(page, lsn); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); } /* Update metapage if needed */ if (info == XLOG_BTREE_UNLINK_PAGE_META) _bt_restore_meta(record, 4); }
static void btree_xlog_mark_page_halfdead(uint8 info, XLogReaderState *record) { XLogRecPtr lsn = record->EndRecPtr; xl_btree_mark_page_halfdead *xlrec = (xl_btree_mark_page_halfdead *) XLogRecGetData(record); Buffer buffer; Page page; BTPageOpaque pageop; IndexTupleData trunctuple; /* * In normal operation, we would lock all the pages this WAL record * touches before changing any of them. In WAL replay, it should be okay * to lock just one page at a time, since no concurrent index updates can * be happening, and readers should not care whether they arrive at the * target page or not (since it's surely empty). */ /* parent page */ if (XLogReadBufferForRedo(record, 1, &buffer) == BLK_NEEDS_REDO) { OffsetNumber poffset; ItemId itemid; IndexTuple itup; OffsetNumber nextoffset; BlockNumber rightsib; page = (Page) BufferGetPage(buffer); pageop = (BTPageOpaque) PageGetSpecialPointer(page); poffset = xlrec->poffset; nextoffset = OffsetNumberNext(poffset); itemid = PageGetItemId(page, nextoffset); itup = (IndexTuple) PageGetItem(page, itemid); rightsib = ItemPointerGetBlockNumber(&itup->t_tid); itemid = PageGetItemId(page, poffset); itup = (IndexTuple) PageGetItem(page, itemid); ItemPointerSet(&(itup->t_tid), rightsib, P_HIKEY); nextoffset = OffsetNumberNext(poffset); PageIndexTupleDelete(page, nextoffset); PageSetLSN(page, lsn); MarkBufferDirty(buffer); } if (BufferIsValid(buffer)) UnlockReleaseBuffer(buffer); /* Rewrite the leaf page as a halfdead page */ buffer = XLogInitBufferForRedo(record, 0); page = (Page) BufferGetPage(buffer); _bt_pageinit(page, BufferGetPageSize(buffer)); pageop = (BTPageOpaque) PageGetSpecialPointer(page); pageop->btpo_prev = xlrec->leftblk; pageop->btpo_next = xlrec->rightblk; pageop->btpo.level = 0; pageop->btpo_flags = BTP_HALF_DEAD | BTP_LEAF; pageop->btpo_cycleid = 0; /* * Construct a dummy hikey item that points to the next parent to be * deleted (if any). */ MemSet(&trunctuple, 0, sizeof(IndexTupleData)); trunctuple.t_info = sizeof(IndexTupleData); if (xlrec->topparent != InvalidBlockNumber) ItemPointerSet(&trunctuple.t_tid, xlrec->topparent, P_HIKEY); else ItemPointerSetInvalid(&trunctuple.t_tid); if (PageAddItem(page, (Item) &trunctuple, sizeof(IndexTupleData), P_HIKEY, false, false) == InvalidOffsetNumber) elog(ERROR, "could not add dummy high key to half-dead page"); PageSetLSN(page, lsn); MarkBufferDirty(buffer); UnlockReleaseBuffer(buffer); }
static void btree_xlog_split(bool onleft, bool isroot, XLogReaderState *record) { XLogRecPtr lsn = record->EndRecPtr; xl_btree_split *xlrec = (xl_btree_split *) XLogRecGetData(record); bool isleaf = (xlrec->level == 0); Buffer lbuf; Buffer rbuf; Page rpage; BTPageOpaque ropaque; char *datapos; Size datalen; Item left_hikey = NULL; Size left_hikeysz = 0; BlockNumber leftsib; BlockNumber rightsib; BlockNumber rnext; XLogRecGetBlockTag(record, 0, NULL, NULL, &leftsib); XLogRecGetBlockTag(record, 1, NULL, NULL, &rightsib); if (!XLogRecGetBlockTag(record, 2, NULL, NULL, &rnext)) rnext = P_NONE; /* * Clear the incomplete split flag on the left sibling of the child page * this is a downlink for. (Like in btree_xlog_insert, this can be done * before locking the other pages) */ if (!isleaf) _bt_clear_incomplete_split(record, 3); /* Reconstruct right (new) sibling page from scratch */ rbuf = XLogInitBufferForRedo(record, 1); datapos = XLogRecGetBlockData(record, 1, &datalen); rpage = (Page) BufferGetPage(rbuf); _bt_pageinit(rpage, BufferGetPageSize(rbuf)); ropaque = (BTPageOpaque) PageGetSpecialPointer(rpage); ropaque->btpo_prev = leftsib; ropaque->btpo_next = rnext; ropaque->btpo.level = xlrec->level; ropaque->btpo_flags = isleaf ? BTP_LEAF : 0; ropaque->btpo_cycleid = 0; _bt_restore_page(rpage, datapos, datalen); /* * On leaf level, the high key of the left page is equal to the first key * on the right page. */ if (isleaf) { ItemId hiItemId = PageGetItemId(rpage, P_FIRSTDATAKEY(ropaque)); left_hikey = PageGetItem(rpage, hiItemId); left_hikeysz = ItemIdGetLength(hiItemId); } PageSetLSN(rpage, lsn); MarkBufferDirty(rbuf); /* don't release the buffer yet; we touch right page's first item below */ /* Now reconstruct left (original) sibling page */ if (XLogReadBufferForRedo(record, 0, &lbuf) == BLK_NEEDS_REDO) { /* * To retain the same physical order of the tuples that they had, we * initialize a temporary empty page for the left page and add all the * items to that in item number order. This mirrors how _bt_split() * works. It's not strictly required to retain the same physical * order, as long as the items are in the correct item number order, * but it helps debugging. See also _bt_restore_page(), which does * the same for the right page. */ Page lpage = (Page) BufferGetPage(lbuf); BTPageOpaque lopaque = (BTPageOpaque) PageGetSpecialPointer(lpage); OffsetNumber off; Item newitem = NULL; Size newitemsz = 0; Page newlpage; OffsetNumber leftoff; datapos = XLogRecGetBlockData(record, 0, &datalen); if (onleft) { newitem = (Item) datapos; newitemsz = MAXALIGN(IndexTupleSize(newitem)); datapos += newitemsz; datalen -= newitemsz; } /* Extract left hikey and its size (assuming 16-bit alignment) */ if (!isleaf) { left_hikey = (Item) datapos; left_hikeysz = MAXALIGN(IndexTupleSize(left_hikey)); datapos += left_hikeysz; datalen -= left_hikeysz; } Assert(datalen == 0); newlpage = PageGetTempPageCopySpecial(lpage); /* Set high key */ leftoff = P_HIKEY; if (PageAddItem(newlpage, left_hikey, left_hikeysz, P_HIKEY, false, false) == InvalidOffsetNumber) elog(PANIC, "failed to add high key to left page after split"); leftoff = OffsetNumberNext(leftoff); for (off = P_FIRSTDATAKEY(lopaque); off < xlrec->firstright; off++) { ItemId itemid; Size itemsz; Item item; /* add the new item if it was inserted on left page */ if (onleft && off == xlrec->newitemoff) { if (PageAddItem(newlpage, newitem, newitemsz, leftoff, false, false) == InvalidOffsetNumber) elog(ERROR, "failed to add new item to left page after split"); leftoff = OffsetNumberNext(leftoff); } itemid = PageGetItemId(lpage, off); itemsz = ItemIdGetLength(itemid); item = PageGetItem(lpage, itemid); if (PageAddItem(newlpage, item, itemsz, leftoff, false, false) == InvalidOffsetNumber) elog(ERROR, "failed to add old item to left page after split"); leftoff = OffsetNumberNext(leftoff); } /* cope with possibility that newitem goes at the end */ if (onleft && off == xlrec->newitemoff) { if (PageAddItem(newlpage, newitem, newitemsz, leftoff, false, false) == InvalidOffsetNumber) elog(ERROR, "failed to add new item to left page after split"); leftoff = OffsetNumberNext(leftoff); } PageRestoreTempPage(newlpage, lpage); /* Fix opaque fields */ lopaque->btpo_flags = BTP_INCOMPLETE_SPLIT; if (isleaf) lopaque->btpo_flags |= BTP_LEAF; lopaque->btpo_next = rightsib; lopaque->btpo_cycleid = 0; PageSetLSN(lpage, lsn); MarkBufferDirty(lbuf); } /* We no longer need the buffers */ if (BufferIsValid(lbuf)) UnlockReleaseBuffer(lbuf); UnlockReleaseBuffer(rbuf); /* * Fix left-link of the page to the right of the new right sibling. * * Note: in normal operation, we do this while still holding lock on the * two split pages. However, that's not necessary for correctness in WAL * replay, because no other index update can be in progress, and readers * will cope properly when following an obsolete left-link. */ if (rnext != P_NONE) { Buffer buffer; if (XLogReadBufferForRedo(record, 2, &buffer) == BLK_NEEDS_REDO) { Page page = (Page) BufferGetPage(buffer); BTPageOpaque pageop = (BTPageOpaque) PageGetSpecialPointer(page); pageop->btpo_prev = rightsib; PageSetLSN(page, lsn); MarkBufferDirty(buffer); } if (BufferIsValid(buffer)) UnlockReleaseBuffer(buffer); } }
/* * _bt_getroot() -- Get the root page of the btree. * * Since the root page can move around the btree file, we have to read * its location from the metadata page, and then read the root page * itself. If no root page exists yet, we have to create one. The * standard class of race conditions exists here; I think I covered * them all in the Hopi Indian rain dance of lock requests below. * * The access type parameter (BT_READ or BT_WRITE) controls whether * a new root page will be created or not. If access = BT_READ, * and no root page exists, we just return InvalidBuffer. For * BT_WRITE, we try to create the root page if it doesn't exist. * NOTE that the returned root page will have only a read lock set * on it even if access = BT_WRITE! * * The returned page is not necessarily the true root --- it could be * a "fast root" (a page that is alone in its level due to deletions). * Also, if the root page is split while we are "in flight" to it, * what we will return is the old root, which is now just the leftmost * page on a probably-not-very-wide level. For most purposes this is * as good as or better than the true root, so we do not bother to * insist on finding the true root. We do, however, guarantee to * return a live (not deleted or half-dead) page. * * On successful return, the root page is pinned and read-locked. * The metadata page is not locked or pinned on exit. */ Buffer _bt_getroot(Relation rel, int access) { Buffer metabuf; Page metapg; BTPageOpaque metaopaque; Buffer rootbuf; Page rootpage; BTPageOpaque rootopaque; BlockNumber rootblkno; uint32 rootlevel; BTMetaPageData *metad; metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_READ); metapg = BufferGetPage(metabuf); metaopaque = (BTPageOpaque) PageGetSpecialPointer(metapg); metad = BTPageGetMeta(metapg); /* sanity-check the metapage */ if (!(metaopaque->btpo_flags & BTP_META) || metad->btm_magic != BTREE_MAGIC) ereport(ERROR, (errcode(ERRCODE_INDEX_CORRUPTED), errmsg("index \"%s\" is not a btree", RelationGetRelationName(rel)))); if (metad->btm_version != BTREE_VERSION) ereport(ERROR, (errcode(ERRCODE_INDEX_CORRUPTED), errmsg("version mismatch in index \"%s\": file version %d, code version %d", RelationGetRelationName(rel), metad->btm_version, BTREE_VERSION))); /* if no root page initialized yet, do it */ if (metad->btm_root == P_NONE) { /* If access = BT_READ, caller doesn't want us to create root yet */ if (access == BT_READ) { _bt_relbuf(rel, metabuf); return InvalidBuffer; } /* trade in our read lock for a write lock */ LockBuffer(metabuf, BUFFER_LOCK_UNLOCK); LockBuffer(metabuf, BT_WRITE); /* * Race condition: if someone else initialized the metadata between * the time we released the read lock and acquired the write lock, we * must avoid doing it again. */ if (metad->btm_root != P_NONE) { /* * Metadata initialized by someone else. In order to guarantee no * deadlocks, we have to release the metadata page and start all * over again. (Is that really true? But it's hardly worth trying * to optimize this case.) */ _bt_relbuf(rel, metabuf); return _bt_getroot(rel, access); } /* * Get, initialize, write, and leave a lock of the appropriate type on * the new root page. Since this is the first page in the tree, it's * a leaf as well as the root. */ rootbuf = _bt_getbuf(rel, P_NEW, BT_WRITE); rootblkno = BufferGetBlockNumber(rootbuf); rootpage = BufferGetPage(rootbuf); _bt_pageinit(rootpage, BufferGetPageSize(rootbuf)); rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage); rootopaque->btpo_prev = rootopaque->btpo_next = P_NONE; rootopaque->btpo_flags = (BTP_LEAF | BTP_ROOT); rootopaque->btpo.level = 0; /* NO ELOG(ERROR) till meta is updated */ START_CRIT_SECTION(); metad->btm_root = rootblkno; metad->btm_level = 0; metad->btm_fastroot = rootblkno; metad->btm_fastlevel = 0; /* XLOG stuff */ if (!rel->rd_istemp) { xl_btree_newroot xlrec; XLogRecPtr recptr; XLogRecData rdata; xlrec.node = rel->rd_node; xlrec.rootblk = rootblkno; xlrec.level = 0; rdata.data = (char *) &xlrec; rdata.len = SizeOfBtreeNewroot; rdata.buffer = InvalidBuffer; rdata.next = NULL; recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_NEWROOT, &rdata); PageSetLSN(rootpage, recptr); PageSetTLI(rootpage, ThisTimeLineID); PageSetLSN(metapg, recptr); PageSetTLI(metapg, ThisTimeLineID); } END_CRIT_SECTION(); _bt_wrtnorelbuf(rel, rootbuf); /* * swap root write lock for read lock. There is no danger of anyone * else accessing the new root page while it's unlocked, since no one * else knows where it is yet. */ LockBuffer(rootbuf, BUFFER_LOCK_UNLOCK); LockBuffer(rootbuf, BT_READ); /* okay, metadata is correct, write and release it */ _bt_wrtbuf(rel, metabuf); } else { rootblkno = metad->btm_fastroot; Assert(rootblkno != P_NONE); rootlevel = metad->btm_fastlevel; /* * We are done with the metapage; arrange to release it via first * _bt_relandgetbuf call */ rootbuf = metabuf; for (;;) { rootbuf = _bt_relandgetbuf(rel, rootbuf, rootblkno, BT_READ); rootpage = BufferGetPage(rootbuf); rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage); if (!P_IGNORE(rootopaque)) break; /* it's dead, Jim. step right one page */ if (P_RIGHTMOST(rootopaque)) elog(ERROR, "no live root page found in \"%s\"", RelationGetRelationName(rel)); rootblkno = rootopaque->btpo_next; } /* Note: can't check btpo.level on deleted pages */ if (rootopaque->btpo.level != rootlevel) elog(ERROR, "root page %u of \"%s\" has level %u, expected %u", rootblkno, RelationGetRelationName(rel), rootopaque->btpo.level, rootlevel); } /* * By here, we have a pin and read lock on the root page, and no lock set * on the metadata page. Return the root page's buffer. */ return rootbuf; }