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ee94300446
Backpatch certain files through 9.1
1865 lines
56 KiB
C
1865 lines
56 KiB
C
/*-------------------------------------------------------------------------
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*
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* nbtpage.c
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* BTree-specific page management code for the Postgres btree access
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* method.
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*
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* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/backend/access/nbtree/nbtpage.c
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*
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* NOTES
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* Postgres btree pages look like ordinary relation pages. The opaque
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* data at high addresses includes pointers to left and right siblings
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* and flag data describing page state. The first page in a btree, page
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* zero, is special -- it stores meta-information describing the tree.
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* Pages one and higher store the actual tree data.
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/nbtree.h"
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#include "access/transam.h"
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#include "access/xlog.h"
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#include "access/xloginsert.h"
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#include "miscadmin.h"
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#include "storage/indexfsm.h"
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#include "storage/lmgr.h"
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#include "storage/predicate.h"
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#include "utils/snapmgr.h"
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static bool _bt_mark_page_halfdead(Relation rel, Buffer buf, BTStack stack);
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static bool _bt_unlink_halfdead_page(Relation rel, Buffer leafbuf,
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bool *rightsib_empty);
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static bool _bt_lock_branch_parent(Relation rel, BlockNumber child,
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BTStack stack, Buffer *topparent, OffsetNumber *topoff,
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BlockNumber *target, BlockNumber *rightsib);
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static void _bt_log_reuse_page(Relation rel, BlockNumber blkno,
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TransactionId latestRemovedXid);
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/*
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* _bt_initmetapage() -- Fill a page buffer with a correct metapage image
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*/
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void
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_bt_initmetapage(Page page, BlockNumber rootbknum, uint32 level)
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{
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BTMetaPageData *metad;
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BTPageOpaque metaopaque;
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_bt_pageinit(page, BLCKSZ);
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metad = BTPageGetMeta(page);
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metad->btm_magic = BTREE_MAGIC;
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metad->btm_version = BTREE_VERSION;
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metad->btm_root = rootbknum;
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metad->btm_level = level;
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metad->btm_fastroot = rootbknum;
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metad->btm_fastlevel = level;
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metaopaque = (BTPageOpaque) PageGetSpecialPointer(page);
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metaopaque->btpo_flags = BTP_META;
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/*
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* Set pd_lower just past the end of the metadata. This is not essential
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* but it makes the page look compressible to xlog.c.
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*/
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((PageHeader) page)->pd_lower =
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((char *) metad + sizeof(BTMetaPageData)) - (char *) page;
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}
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/*
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* _bt_getroot() -- Get the root page of the btree.
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*
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* Since the root page can move around the btree file, we have to read
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* its location from the metadata page, and then read the root page
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* itself. If no root page exists yet, we have to create one. The
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* standard class of race conditions exists here; I think I covered
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* them all in the Hopi Indian rain dance of lock requests below.
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*
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* The access type parameter (BT_READ or BT_WRITE) controls whether
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* a new root page will be created or not. If access = BT_READ,
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* and no root page exists, we just return InvalidBuffer. For
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* BT_WRITE, we try to create the root page if it doesn't exist.
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* NOTE that the returned root page will have only a read lock set
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* on it even if access = BT_WRITE!
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*
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* The returned page is not necessarily the true root --- it could be
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* a "fast root" (a page that is alone in its level due to deletions).
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* Also, if the root page is split while we are "in flight" to it,
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* what we will return is the old root, which is now just the leftmost
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* page on a probably-not-very-wide level. For most purposes this is
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* as good as or better than the true root, so we do not bother to
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* insist on finding the true root. We do, however, guarantee to
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* return a live (not deleted or half-dead) page.
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*
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* On successful return, the root page is pinned and read-locked.
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* The metadata page is not locked or pinned on exit.
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*/
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Buffer
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_bt_getroot(Relation rel, int access)
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{
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Buffer metabuf;
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Page metapg;
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BTPageOpaque metaopaque;
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Buffer rootbuf;
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Page rootpage;
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BTPageOpaque rootopaque;
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BlockNumber rootblkno;
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uint32 rootlevel;
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BTMetaPageData *metad;
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/*
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* Try to use previously-cached metapage data to find the root. This
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* normally saves one buffer access per index search, which is a very
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* helpful savings in bufmgr traffic and hence contention.
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*/
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if (rel->rd_amcache != NULL)
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{
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metad = (BTMetaPageData *) rel->rd_amcache;
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/* We shouldn't have cached it if any of these fail */
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Assert(metad->btm_magic == BTREE_MAGIC);
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Assert(metad->btm_version == BTREE_VERSION);
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Assert(metad->btm_root != P_NONE);
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rootblkno = metad->btm_fastroot;
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Assert(rootblkno != P_NONE);
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rootlevel = metad->btm_fastlevel;
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rootbuf = _bt_getbuf(rel, rootblkno, BT_READ);
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rootpage = BufferGetPage(rootbuf);
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rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage);
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/*
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* Since the cache might be stale, we check the page more carefully
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* here than normal. We *must* check that it's not deleted. If it's
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* not alone on its level, then we reject too --- this may be overly
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* paranoid but better safe than sorry. Note we don't check P_ISROOT,
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* because that's not set in a "fast root".
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*/
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if (!P_IGNORE(rootopaque) &&
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rootopaque->btpo.level == rootlevel &&
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P_LEFTMOST(rootopaque) &&
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P_RIGHTMOST(rootopaque))
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{
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/* OK, accept cached page as the root */
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return rootbuf;
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}
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_bt_relbuf(rel, rootbuf);
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/* Cache is stale, throw it away */
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if (rel->rd_amcache)
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pfree(rel->rd_amcache);
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rel->rd_amcache = NULL;
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}
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metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_READ);
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metapg = BufferGetPage(metabuf);
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metaopaque = (BTPageOpaque) PageGetSpecialPointer(metapg);
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metad = BTPageGetMeta(metapg);
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/* sanity-check the metapage */
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if (!(metaopaque->btpo_flags & BTP_META) ||
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metad->btm_magic != BTREE_MAGIC)
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ereport(ERROR,
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(errcode(ERRCODE_INDEX_CORRUPTED),
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errmsg("index \"%s\" is not a btree",
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RelationGetRelationName(rel))));
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if (metad->btm_version != BTREE_VERSION)
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ereport(ERROR,
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(errcode(ERRCODE_INDEX_CORRUPTED),
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errmsg("version mismatch in index \"%s\": file version %d, code version %d",
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RelationGetRelationName(rel),
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metad->btm_version, BTREE_VERSION)));
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/* if no root page initialized yet, do it */
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if (metad->btm_root == P_NONE)
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{
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/* If access = BT_READ, caller doesn't want us to create root yet */
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if (access == BT_READ)
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{
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_bt_relbuf(rel, metabuf);
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return InvalidBuffer;
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}
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/* trade in our read lock for a write lock */
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LockBuffer(metabuf, BUFFER_LOCK_UNLOCK);
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LockBuffer(metabuf, BT_WRITE);
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/*
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* Race condition: if someone else initialized the metadata between
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* the time we released the read lock and acquired the write lock, we
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* must avoid doing it again.
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*/
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if (metad->btm_root != P_NONE)
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{
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/*
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* Metadata initialized by someone else. In order to guarantee no
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* deadlocks, we have to release the metadata page and start all
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* over again. (Is that really true? But it's hardly worth trying
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* to optimize this case.)
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*/
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_bt_relbuf(rel, metabuf);
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return _bt_getroot(rel, access);
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}
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/*
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* Get, initialize, write, and leave a lock of the appropriate type on
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* the new root page. Since this is the first page in the tree, it's
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* a leaf as well as the root.
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*/
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rootbuf = _bt_getbuf(rel, P_NEW, BT_WRITE);
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rootblkno = BufferGetBlockNumber(rootbuf);
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rootpage = BufferGetPage(rootbuf);
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rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage);
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rootopaque->btpo_prev = rootopaque->btpo_next = P_NONE;
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rootopaque->btpo_flags = (BTP_LEAF | BTP_ROOT);
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rootopaque->btpo.level = 0;
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rootopaque->btpo_cycleid = 0;
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/* NO ELOG(ERROR) till meta is updated */
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START_CRIT_SECTION();
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metad->btm_root = rootblkno;
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metad->btm_level = 0;
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metad->btm_fastroot = rootblkno;
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metad->btm_fastlevel = 0;
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MarkBufferDirty(rootbuf);
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MarkBufferDirty(metabuf);
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/* XLOG stuff */
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if (RelationNeedsWAL(rel))
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{
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xl_btree_newroot xlrec;
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XLogRecPtr recptr;
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xl_btree_metadata md;
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XLogBeginInsert();
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XLogRegisterBuffer(0, rootbuf, REGBUF_WILL_INIT);
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XLogRegisterBuffer(2, metabuf, REGBUF_WILL_INIT);
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md.root = rootblkno;
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md.level = 0;
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md.fastroot = rootblkno;
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md.fastlevel = 0;
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XLogRegisterBufData(2, (char *) &md, sizeof(xl_btree_metadata));
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xlrec.rootblk = rootblkno;
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xlrec.level = 0;
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XLogRegisterData((char *) &xlrec, SizeOfBtreeNewroot);
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recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_NEWROOT);
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PageSetLSN(rootpage, recptr);
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PageSetLSN(metapg, recptr);
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}
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END_CRIT_SECTION();
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/*
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* swap root write lock for read lock. There is no danger of anyone
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* else accessing the new root page while it's unlocked, since no one
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* else knows where it is yet.
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*/
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LockBuffer(rootbuf, BUFFER_LOCK_UNLOCK);
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LockBuffer(rootbuf, BT_READ);
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/* okay, metadata is correct, release lock on it */
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_bt_relbuf(rel, metabuf);
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}
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else
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{
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rootblkno = metad->btm_fastroot;
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Assert(rootblkno != P_NONE);
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rootlevel = metad->btm_fastlevel;
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/*
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* Cache the metapage data for next time
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*/
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rel->rd_amcache = MemoryContextAlloc(rel->rd_indexcxt,
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sizeof(BTMetaPageData));
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memcpy(rel->rd_amcache, metad, sizeof(BTMetaPageData));
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/*
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* We are done with the metapage; arrange to release it via first
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* _bt_relandgetbuf call
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*/
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rootbuf = metabuf;
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for (;;)
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{
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rootbuf = _bt_relandgetbuf(rel, rootbuf, rootblkno, BT_READ);
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rootpage = BufferGetPage(rootbuf);
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rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage);
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if (!P_IGNORE(rootopaque))
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break;
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/* it's dead, Jim. step right one page */
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if (P_RIGHTMOST(rootopaque))
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elog(ERROR, "no live root page found in index \"%s\"",
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RelationGetRelationName(rel));
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rootblkno = rootopaque->btpo_next;
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}
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/* Note: can't check btpo.level on deleted pages */
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if (rootopaque->btpo.level != rootlevel)
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elog(ERROR, "root page %u of index \"%s\" has level %u, expected %u",
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rootblkno, RelationGetRelationName(rel),
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rootopaque->btpo.level, rootlevel);
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}
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/*
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* By here, we have a pin and read lock on the root page, and no lock set
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* on the metadata page. Return the root page's buffer.
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*/
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return rootbuf;
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}
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/*
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* _bt_gettrueroot() -- Get the true root page of the btree.
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*
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* This is the same as the BT_READ case of _bt_getroot(), except
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* we follow the true-root link not the fast-root link.
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*
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* By the time we acquire lock on the root page, it might have been split and
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* not be the true root anymore. This is okay for the present uses of this
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* routine; we only really need to be able to move up at least one tree level
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* from whatever non-root page we were at. If we ever do need to lock the
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* one true root page, we could loop here, re-reading the metapage on each
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* failure. (Note that it wouldn't do to hold the lock on the metapage while
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* moving to the root --- that'd deadlock against any concurrent root split.)
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*/
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Buffer
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_bt_gettrueroot(Relation rel)
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{
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Buffer metabuf;
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Page metapg;
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BTPageOpaque metaopaque;
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Buffer rootbuf;
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Page rootpage;
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BTPageOpaque rootopaque;
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BlockNumber rootblkno;
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uint32 rootlevel;
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BTMetaPageData *metad;
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/*
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* We don't try to use cached metapage data here, since (a) this path is
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* not performance-critical, and (b) if we are here it suggests our cache
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* is out-of-date anyway. In light of point (b), it's probably safest to
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* actively flush any cached metapage info.
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*/
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if (rel->rd_amcache)
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pfree(rel->rd_amcache);
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rel->rd_amcache = NULL;
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metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_READ);
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metapg = BufferGetPage(metabuf);
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metaopaque = (BTPageOpaque) PageGetSpecialPointer(metapg);
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metad = BTPageGetMeta(metapg);
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if (!(metaopaque->btpo_flags & BTP_META) ||
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metad->btm_magic != BTREE_MAGIC)
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ereport(ERROR,
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(errcode(ERRCODE_INDEX_CORRUPTED),
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errmsg("index \"%s\" is not a btree",
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RelationGetRelationName(rel))));
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if (metad->btm_version != BTREE_VERSION)
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ereport(ERROR,
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(errcode(ERRCODE_INDEX_CORRUPTED),
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errmsg("version mismatch in index \"%s\": file version %d, code version %d",
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RelationGetRelationName(rel),
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metad->btm_version, BTREE_VERSION)));
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/* if no root page initialized yet, fail */
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if (metad->btm_root == P_NONE)
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{
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_bt_relbuf(rel, metabuf);
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return InvalidBuffer;
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}
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rootblkno = metad->btm_root;
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rootlevel = metad->btm_level;
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|
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/*
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* We are done with the metapage; arrange to release it via first
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* _bt_relandgetbuf call
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*/
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rootbuf = metabuf;
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for (;;)
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{
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rootbuf = _bt_relandgetbuf(rel, rootbuf, rootblkno, BT_READ);
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rootpage = BufferGetPage(rootbuf);
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rootopaque = (BTPageOpaque) PageGetSpecialPointer(rootpage);
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|
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if (!P_IGNORE(rootopaque))
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break;
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|
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/* it's dead, Jim. step right one page */
|
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if (P_RIGHTMOST(rootopaque))
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elog(ERROR, "no live root page found in index \"%s\"",
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RelationGetRelationName(rel));
|
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rootblkno = rootopaque->btpo_next;
|
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}
|
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|
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/* Note: can't check btpo.level on deleted pages */
|
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if (rootopaque->btpo.level != rootlevel)
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elog(ERROR, "root page %u of index \"%s\" has level %u, expected %u",
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rootblkno, RelationGetRelationName(rel),
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rootopaque->btpo.level, rootlevel);
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return rootbuf;
|
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}
|
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|
|
/*
|
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* _bt_getrootheight() -- Get the height of the btree search tree.
|
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*
|
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* We return the level (counting from zero) of the current fast root.
|
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* This represents the number of tree levels we'd have to descend through
|
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* to start any btree index search.
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*
|
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* This is used by the planner for cost-estimation purposes. Since it's
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* only an estimate, slightly-stale data is fine, hence we don't worry
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* about updating previously cached data.
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*/
|
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int
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_bt_getrootheight(Relation rel)
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{
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BTMetaPageData *metad;
|
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|
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/*
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* We can get what we need from the cached metapage data. If it's not
|
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* cached yet, load it. Sanity checks here must match _bt_getroot().
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*/
|
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if (rel->rd_amcache == NULL)
|
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{
|
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Buffer metabuf;
|
|
Page metapg;
|
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BTPageOpaque metaopaque;
|
|
|
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metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_READ);
|
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metapg = BufferGetPage(metabuf);
|
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metaopaque = (BTPageOpaque) PageGetSpecialPointer(metapg);
|
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metad = BTPageGetMeta(metapg);
|
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|
|
/* sanity-check the metapage */
|
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if (!(metaopaque->btpo_flags & BTP_META) ||
|
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metad->btm_magic != BTREE_MAGIC)
|
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ereport(ERROR,
|
|
(errcode(ERRCODE_INDEX_CORRUPTED),
|
|
errmsg("index \"%s\" is not a btree",
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RelationGetRelationName(rel))));
|
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|
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if (metad->btm_version != BTREE_VERSION)
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ereport(ERROR,
|
|
(errcode(ERRCODE_INDEX_CORRUPTED),
|
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errmsg("version mismatch in index \"%s\": file version %d, code version %d",
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RelationGetRelationName(rel),
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metad->btm_version, BTREE_VERSION)));
|
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|
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/*
|
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* If there's no root page yet, _bt_getroot() doesn't expect a cache
|
|
* to be made, so just stop here and report the index height is zero.
|
|
* (XXX perhaps _bt_getroot() should be changed to allow this case.)
|
|
*/
|
|
if (metad->btm_root == P_NONE)
|
|
{
|
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_bt_relbuf(rel, metabuf);
|
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return 0;
|
|
}
|
|
|
|
/*
|
|
* Cache the metapage data for next time
|
|
*/
|
|
rel->rd_amcache = MemoryContextAlloc(rel->rd_indexcxt,
|
|
sizeof(BTMetaPageData));
|
|
memcpy(rel->rd_amcache, metad, sizeof(BTMetaPageData));
|
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|
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_bt_relbuf(rel, metabuf);
|
|
}
|
|
|
|
metad = (BTMetaPageData *) rel->rd_amcache;
|
|
/* We shouldn't have cached it if any of these fail */
|
|
Assert(metad->btm_magic == BTREE_MAGIC);
|
|
Assert(metad->btm_version == BTREE_VERSION);
|
|
Assert(metad->btm_fastroot != P_NONE);
|
|
|
|
return metad->btm_fastlevel;
|
|
}
|
|
|
|
/*
|
|
* _bt_checkpage() -- Verify that a freshly-read page looks sane.
|
|
*/
|
|
void
|
|
_bt_checkpage(Relation rel, Buffer buf)
|
|
{
|
|
Page page = BufferGetPage(buf);
|
|
|
|
/*
|
|
* ReadBuffer verifies that every newly-read page passes
|
|
* PageHeaderIsValid, which means it either contains a reasonably sane
|
|
* page header or is all-zero. We have to defend against the all-zero
|
|
* case, however.
|
|
*/
|
|
if (PageIsNew(page))
|
|
ereport(ERROR,
|
|
(errcode(ERRCODE_INDEX_CORRUPTED),
|
|
errmsg("index \"%s\" contains unexpected zero page at block %u",
|
|
RelationGetRelationName(rel),
|
|
BufferGetBlockNumber(buf)),
|
|
errhint("Please REINDEX it.")));
|
|
|
|
/*
|
|
* Additionally check that the special area looks sane.
|
|
*/
|
|
if (PageGetSpecialSize(page) != MAXALIGN(sizeof(BTPageOpaqueData)))
|
|
ereport(ERROR,
|
|
(errcode(ERRCODE_INDEX_CORRUPTED),
|
|
errmsg("index \"%s\" contains corrupted page at block %u",
|
|
RelationGetRelationName(rel),
|
|
BufferGetBlockNumber(buf)),
|
|
errhint("Please REINDEX it.")));
|
|
}
|
|
|
|
/*
|
|
* Log the reuse of a page from the FSM.
|
|
*/
|
|
static void
|
|
_bt_log_reuse_page(Relation rel, BlockNumber blkno, TransactionId latestRemovedXid)
|
|
{
|
|
xl_btree_reuse_page xlrec_reuse;
|
|
|
|
/*
|
|
* Note that we don't register the buffer with the record, because this
|
|
* operation doesn't modify the page. This record only exists to provide a
|
|
* conflict point for Hot Standby.
|
|
*/
|
|
|
|
/* XLOG stuff */
|
|
xlrec_reuse.node = rel->rd_node;
|
|
xlrec_reuse.block = blkno;
|
|
xlrec_reuse.latestRemovedXid = latestRemovedXid;
|
|
|
|
XLogBeginInsert();
|
|
XLogRegisterData((char *) &xlrec_reuse, SizeOfBtreeReusePage);
|
|
|
|
XLogInsert(RM_BTREE_ID, XLOG_BTREE_REUSE_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;
|
|
|
|
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);
|
|
if (blkno == InvalidBlockNumber)
|
|
break;
|
|
buf = ReadBuffer(rel, blkno);
|
|
if (ConditionalLockBuffer(buf))
|
|
{
|
|
page = BufferGetPage(buf);
|
|
if (_bt_page_recyclable(page))
|
|
{
|
|
/*
|
|
* If we are generating WAL for Hot Standby then create a
|
|
* WAL record that will allow us to conflict with queries
|
|
* running on standby.
|
|
*/
|
|
if (XLogStandbyInfoActive() && RelationNeedsWAL(rel))
|
|
{
|
|
BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
_bt_log_reuse_page(rel, blkno, opaque->btpo.xact);
|
|
}
|
|
|
|
/* 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(page));
|
|
_bt_pageinit(page, BufferGetPageSize(buf));
|
|
}
|
|
|
|
/* ref count and lock type are correct */
|
|
return buf;
|
|
}
|
|
|
|
/*
|
|
* _bt_relandgetbuf() -- release a locked buffer and get another one.
|
|
*
|
|
* This is equivalent to _bt_relbuf followed by _bt_getbuf, with the
|
|
* exception that blkno may not be P_NEW. Also, if obuf is InvalidBuffer
|
|
* then it reduces to just _bt_getbuf; allowing this case simplifies some
|
|
* callers.
|
|
*
|
|
* The original motivation for using this was to avoid two entries to the
|
|
* bufmgr when one would do. However, now it's mainly just a notational
|
|
* convenience. The only case where it saves work over _bt_relbuf/_bt_getbuf
|
|
* is when the target page is the same one already in the buffer.
|
|
*/
|
|
Buffer
|
|
_bt_relandgetbuf(Relation rel, Buffer obuf, BlockNumber blkno, int access)
|
|
{
|
|
Buffer buf;
|
|
|
|
Assert(blkno != P_NEW);
|
|
if (BufferIsValid(obuf))
|
|
LockBuffer(obuf, BUFFER_LOCK_UNLOCK);
|
|
buf = ReleaseAndReadBuffer(obuf, rel, blkno);
|
|
LockBuffer(buf, access);
|
|
_bt_checkpage(rel, buf);
|
|
return buf;
|
|
}
|
|
|
|
/*
|
|
* _bt_relbuf() -- release a locked buffer.
|
|
*
|
|
* Lock and pin (refcount) are both dropped.
|
|
*/
|
|
void
|
|
_bt_relbuf(Relation rel, Buffer buf)
|
|
{
|
|
UnlockReleaseBuffer(buf);
|
|
}
|
|
|
|
/*
|
|
* _bt_pageinit() -- Initialize a new page.
|
|
*
|
|
* On return, the page header is initialized; data space is empty;
|
|
* special space is zeroed out.
|
|
*/
|
|
void
|
|
_bt_pageinit(Page page, Size size)
|
|
{
|
|
PageInit(page, size, sizeof(BTPageOpaqueData));
|
|
}
|
|
|
|
/*
|
|
* _bt_page_recyclable() -- Is an existing page recyclable?
|
|
*
|
|
* This exists to make sure _bt_getbuf and btvacuumscan have the same
|
|
* policy about whether a page is safe to re-use.
|
|
*/
|
|
bool
|
|
_bt_page_recyclable(Page page)
|
|
{
|
|
BTPageOpaque opaque;
|
|
|
|
/*
|
|
* It's possible to find an all-zeroes page in an index --- for example, a
|
|
* backend might successfully extend the relation one page and then crash
|
|
* before it is able to make a WAL entry for adding the page. If we find a
|
|
* zeroed page then reclaim it.
|
|
*/
|
|
if (PageIsNew(page))
|
|
return true;
|
|
|
|
/*
|
|
* Otherwise, recycle if deleted and too old to have any processes
|
|
* interested in it.
|
|
*/
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
if (P_ISDELETED(opaque) &&
|
|
TransactionIdPrecedes(opaque->btpo.xact, RecentGlobalXmin))
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* Delete item(s) from a btree page during VACUUM.
|
|
*
|
|
* This must only be used for deleting leaf items. Deleting an item on a
|
|
* non-leaf page has to be done as part of an atomic action that includes
|
|
* deleting the page it points to.
|
|
*
|
|
* This routine assumes that the caller has pinned and locked the buffer.
|
|
* Also, the given itemnos *must* appear in increasing order in the array.
|
|
*
|
|
* We record VACUUMs and b-tree deletes differently in WAL. InHotStandby
|
|
* we need to be able to pin all of the blocks in the btree in physical
|
|
* order when replaying the effects of a VACUUM, just as we do for the
|
|
* original VACUUM itself. lastBlockVacuumed allows us to tell whether an
|
|
* intermediate range of blocks has had no changes at all by VACUUM,
|
|
* and so must be scanned anyway during replay. We always write a WAL record
|
|
* for the last block in the index, whether or not it contained any items
|
|
* to be removed. This allows us to scan right up to end of index to
|
|
* ensure correct locking.
|
|
*/
|
|
void
|
|
_bt_delitems_vacuum(Relation rel, Buffer buf,
|
|
OffsetNumber *itemnos, int nitems,
|
|
BlockNumber lastBlockVacuumed)
|
|
{
|
|
Page page = BufferGetPage(buf);
|
|
BTPageOpaque opaque;
|
|
|
|
/* No ereport(ERROR) until changes are logged */
|
|
START_CRIT_SECTION();
|
|
|
|
/* Fix the page */
|
|
if (nitems > 0)
|
|
PageIndexMultiDelete(page, itemnos, nitems);
|
|
|
|
/*
|
|
* We can clear the vacuum cycle ID since this page has certainly been
|
|
* processed by the current vacuum scan.
|
|
*/
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
opaque->btpo_cycleid = 0;
|
|
|
|
/*
|
|
* Mark the page as not containing any LP_DEAD items. This is not
|
|
* certainly true (there might be some that have recently been marked, but
|
|
* weren't included in our target-item list), but it will almost always be
|
|
* true and it doesn't seem worth an additional page scan to check it.
|
|
* Remember that BTP_HAS_GARBAGE is only a hint anyway.
|
|
*/
|
|
opaque->btpo_flags &= ~BTP_HAS_GARBAGE;
|
|
|
|
MarkBufferDirty(buf);
|
|
|
|
/* XLOG stuff */
|
|
if (RelationNeedsWAL(rel))
|
|
{
|
|
XLogRecPtr recptr;
|
|
xl_btree_vacuum xlrec_vacuum;
|
|
|
|
xlrec_vacuum.lastBlockVacuumed = lastBlockVacuumed;
|
|
|
|
XLogBeginInsert();
|
|
XLogRegisterBuffer(0, buf, REGBUF_STANDARD);
|
|
XLogRegisterData((char *) &xlrec_vacuum, SizeOfBtreeVacuum);
|
|
|
|
/*
|
|
* The target-offsets array is not in the buffer, but pretend that it
|
|
* is. When XLogInsert stores the whole buffer, the offsets array
|
|
* need not be stored too.
|
|
*/
|
|
if (nitems > 0)
|
|
XLogRegisterBufData(0, (char *) itemnos, nitems * sizeof(OffsetNumber));
|
|
|
|
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_VACUUM);
|
|
|
|
PageSetLSN(page, recptr);
|
|
}
|
|
|
|
END_CRIT_SECTION();
|
|
}
|
|
|
|
/*
|
|
* Delete item(s) from a btree page during single-page cleanup.
|
|
*
|
|
* As above, must only be used on leaf pages.
|
|
*
|
|
* This routine assumes that the caller has pinned and locked the buffer.
|
|
* Also, the given itemnos *must* appear in increasing order in the array.
|
|
*
|
|
* This is nearly the same as _bt_delitems_vacuum as far as what it does to
|
|
* the page, but the WAL logging considerations are quite different. See
|
|
* comments for _bt_delitems_vacuum.
|
|
*/
|
|
void
|
|
_bt_delitems_delete(Relation rel, Buffer buf,
|
|
OffsetNumber *itemnos, int nitems,
|
|
Relation heapRel)
|
|
{
|
|
Page page = BufferGetPage(buf);
|
|
BTPageOpaque opaque;
|
|
|
|
/* Shouldn't be called unless there's something to do */
|
|
Assert(nitems > 0);
|
|
|
|
/* No ereport(ERROR) until changes are logged */
|
|
START_CRIT_SECTION();
|
|
|
|
/* Fix the page */
|
|
PageIndexMultiDelete(page, itemnos, nitems);
|
|
|
|
/*
|
|
* Unlike _bt_delitems_vacuum, we *must not* clear the vacuum cycle ID,
|
|
* because this is not called by VACUUM.
|
|
*/
|
|
|
|
/*
|
|
* Mark the page as not containing any LP_DEAD items. This is not
|
|
* certainly true (there might be some that have recently been marked, but
|
|
* weren't included in our target-item list), but it will almost always be
|
|
* true and it doesn't seem worth an additional page scan to check it.
|
|
* Remember that BTP_HAS_GARBAGE is only a hint anyway.
|
|
*/
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
opaque->btpo_flags &= ~BTP_HAS_GARBAGE;
|
|
|
|
MarkBufferDirty(buf);
|
|
|
|
/* XLOG stuff */
|
|
if (RelationNeedsWAL(rel))
|
|
{
|
|
XLogRecPtr recptr;
|
|
xl_btree_delete xlrec_delete;
|
|
|
|
xlrec_delete.hnode = heapRel->rd_node;
|
|
xlrec_delete.nitems = nitems;
|
|
|
|
XLogBeginInsert();
|
|
XLogRegisterBuffer(0, buf, REGBUF_STANDARD);
|
|
XLogRegisterData((char *) &xlrec_delete, SizeOfBtreeDelete);
|
|
|
|
/*
|
|
* We need the target-offsets array whether or not we store the whole
|
|
* buffer, to allow us to find the latestRemovedXid on a standby
|
|
* server.
|
|
*/
|
|
XLogRegisterData((char *) itemnos, nitems * sizeof(OffsetNumber));
|
|
|
|
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_DELETE);
|
|
|
|
PageSetLSN(page, recptr);
|
|
}
|
|
|
|
END_CRIT_SECTION();
|
|
}
|
|
|
|
/*
|
|
* Returns true, if the given block has the half-dead flag set.
|
|
*/
|
|
static bool
|
|
_bt_is_page_halfdead(Relation rel, BlockNumber blk)
|
|
{
|
|
Buffer buf;
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
bool result;
|
|
|
|
buf = _bt_getbuf(rel, blk, BT_READ);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
result = P_ISHALFDEAD(opaque);
|
|
_bt_relbuf(rel, buf);
|
|
|
|
return result;
|
|
}
|
|
|
|
/*
|
|
* Subroutine to find the parent of the branch we're deleting. This climbs
|
|
* up the tree until it finds a page with more than one child, i.e. a page
|
|
* that will not be totally emptied by the deletion. The chain of pages below
|
|
* it, with one downlink each, will form the branch that we need to delete.
|
|
*
|
|
* If we cannot remove the downlink from the parent, because it's the
|
|
* rightmost entry, returns false. On success, *topparent and *topoff are set
|
|
* to the buffer holding the parent, and the offset of the downlink in it.
|
|
* *topparent is write-locked, the caller is responsible for releasing it when
|
|
* done. *target is set to the topmost page in the branch to-be-deleted, i.e.
|
|
* the page whose downlink *topparent / *topoff point to, and *rightsib to its
|
|
* right sibling.
|
|
*
|
|
* "child" is the leaf page we wish to delete, and "stack" is a search stack
|
|
* leading to it (approximately). Note that we will update the stack
|
|
* entry(s) to reflect current downlink positions --- this is harmless and
|
|
* indeed saves later search effort in _bt_pagedel. The caller should
|
|
* initialize *target and *rightsib to the leaf page and its right sibling.
|
|
*
|
|
* Note: it's OK to release page locks on any internal pages between the leaf
|
|
* and *topparent, because a safe deletion can't become unsafe due to
|
|
* concurrent activity. An internal page can only acquire an entry if the
|
|
* child is split, but that cannot happen as long as we hold a lock on the
|
|
* leaf.
|
|
*/
|
|
static bool
|
|
_bt_lock_branch_parent(Relation rel, BlockNumber child, BTStack stack,
|
|
Buffer *topparent, OffsetNumber *topoff,
|
|
BlockNumber *target, BlockNumber *rightsib)
|
|
{
|
|
BlockNumber parent;
|
|
OffsetNumber poffset,
|
|
maxoff;
|
|
Buffer pbuf;
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
BlockNumber leftsib;
|
|
|
|
/*
|
|
* Locate the downlink of "child" in the parent (updating the stack entry
|
|
* if needed)
|
|
*/
|
|
ItemPointerSet(&(stack->bts_btentry.t_tid), child, P_HIKEY);
|
|
pbuf = _bt_getstackbuf(rel, stack, BT_WRITE);
|
|
if (pbuf == InvalidBuffer)
|
|
elog(ERROR, "failed to re-find parent key in index \"%s\" for deletion target page %u",
|
|
RelationGetRelationName(rel), child);
|
|
parent = stack->bts_blkno;
|
|
poffset = stack->bts_offset;
|
|
|
|
page = BufferGetPage(pbuf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
maxoff = PageGetMaxOffsetNumber(page);
|
|
|
|
/*
|
|
* If the target is the rightmost child of its parent, then we can't
|
|
* delete, unless it's also the only child.
|
|
*/
|
|
if (poffset >= maxoff)
|
|
{
|
|
/* It's rightmost child... */
|
|
if (poffset == P_FIRSTDATAKEY(opaque))
|
|
{
|
|
/*
|
|
* It's only child, so safe if parent would itself be removable.
|
|
* We have to check the parent itself, and then recurse to test
|
|
* the conditions at the parent's parent.
|
|
*/
|
|
if (P_RIGHTMOST(opaque) || P_ISROOT(opaque) ||
|
|
P_INCOMPLETE_SPLIT(opaque))
|
|
{
|
|
_bt_relbuf(rel, pbuf);
|
|
return false;
|
|
}
|
|
|
|
*target = parent;
|
|
*rightsib = opaque->btpo_next;
|
|
leftsib = opaque->btpo_prev;
|
|
|
|
_bt_relbuf(rel, pbuf);
|
|
|
|
/*
|
|
* Like in _bt_pagedel, check that the left sibling is not marked
|
|
* with INCOMPLETE_SPLIT flag. That would mean that there is no
|
|
* downlink to the page to be deleted, and the page deletion
|
|
* algorithm isn't prepared to handle that.
|
|
*/
|
|
if (leftsib != P_NONE)
|
|
{
|
|
Buffer lbuf;
|
|
Page lpage;
|
|
BTPageOpaque lopaque;
|
|
|
|
lbuf = _bt_getbuf(rel, leftsib, BT_READ);
|
|
lpage = BufferGetPage(lbuf);
|
|
lopaque = (BTPageOpaque) PageGetSpecialPointer(lpage);
|
|
|
|
/*
|
|
* If the left sibling was concurrently split, so that its
|
|
* next-pointer doesn't point to the current page anymore, the
|
|
* split that created the current page must be completed. (We
|
|
* don't allow splitting an incompletely split page again
|
|
* until the previous split has been completed)
|
|
*/
|
|
if (lopaque->btpo_next == parent &&
|
|
P_INCOMPLETE_SPLIT(lopaque))
|
|
{
|
|
_bt_relbuf(rel, lbuf);
|
|
return false;
|
|
}
|
|
_bt_relbuf(rel, lbuf);
|
|
}
|
|
|
|
/*
|
|
* Perform the same check on this internal level that
|
|
* _bt_mark_page_halfdead performed on the leaf level.
|
|
*/
|
|
if (_bt_is_page_halfdead(rel, *rightsib))
|
|
{
|
|
elog(DEBUG1, "could not delete page %u because its right sibling %u is half-dead",
|
|
parent, *rightsib);
|
|
return false;
|
|
}
|
|
|
|
return _bt_lock_branch_parent(rel, parent, stack->bts_parent,
|
|
topparent, topoff, target, rightsib);
|
|
}
|
|
else
|
|
{
|
|
/* Unsafe to delete */
|
|
_bt_relbuf(rel, pbuf);
|
|
return false;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/* Not rightmost child, so safe to delete */
|
|
*topparent = pbuf;
|
|
*topoff = poffset;
|
|
return true;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* _bt_pagedel() -- Delete a page from the b-tree, if legal to do so.
|
|
*
|
|
* This action unlinks the page from the b-tree structure, removing all
|
|
* pointers leading to it --- but not touching its own left and right links.
|
|
* The page cannot be physically reclaimed right away, since other processes
|
|
* may currently be trying to follow links leading to the page; they have to
|
|
* be allowed to use its right-link to recover. See nbtree/README.
|
|
*
|
|
* On entry, the target buffer must be pinned and locked (either read or write
|
|
* lock is OK). This lock and pin will be dropped before exiting.
|
|
*
|
|
* Returns the number of pages successfully deleted (zero if page cannot
|
|
* be deleted now; could be more than one if parent or sibling pages were
|
|
* deleted too).
|
|
*
|
|
* NOTE: this leaks memory. Rather than trying to clean up everything
|
|
* carefully, it's better to run it in a temp context that can be reset
|
|
* frequently.
|
|
*/
|
|
int
|
|
_bt_pagedel(Relation rel, Buffer buf)
|
|
{
|
|
int ndeleted = 0;
|
|
BlockNumber rightsib;
|
|
bool rightsib_empty;
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
|
|
/*
|
|
* "stack" is a search stack leading (approximately) to the target page.
|
|
* It is initially NULL, but when iterating, we keep it to avoid
|
|
* duplicated search effort.
|
|
*
|
|
* Also, when "stack" is not NULL, we have already checked that the
|
|
* current page is not the right half of an incomplete split, i.e. the
|
|
* left sibling does not have its INCOMPLETE_SPLIT flag set.
|
|
*/
|
|
BTStack stack = NULL;
|
|
|
|
for (;;)
|
|
{
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
/*
|
|
* Internal pages are never deleted directly, only as part of deleting
|
|
* the whole branch all the way down to leaf level.
|
|
*/
|
|
if (!P_ISLEAF(opaque))
|
|
{
|
|
/*
|
|
* Pre-9.4 page deletion only marked internal pages as half-dead,
|
|
* but now we only use that flag on leaf pages. The old algorithm
|
|
* was never supposed to leave half-dead pages in the tree, it was
|
|
* just a transient state, but it was nevertheless possible in
|
|
* error scenarios. We don't know how to deal with them here. They
|
|
* are harmless as far as searches are considered, but inserts
|
|
* into the deleted keyspace could add out-of-order downlinks in
|
|
* the upper levels. Log a notice, hopefully the admin will notice
|
|
* and reindex.
|
|
*/
|
|
if (P_ISHALFDEAD(opaque))
|
|
ereport(LOG,
|
|
(errcode(ERRCODE_INDEX_CORRUPTED),
|
|
errmsg("index \"%s\" contains a half-dead internal page",
|
|
RelationGetRelationName(rel)),
|
|
errhint("This can be caused by an interrupted VACUUM in version 9.3 or older, before upgrade. Please REINDEX it.")));
|
|
_bt_relbuf(rel, buf);
|
|
return ndeleted;
|
|
}
|
|
|
|
/*
|
|
* We can never delete rightmost pages nor root pages. While at it,
|
|
* check that page is not already deleted and is empty.
|
|
*
|
|
* To keep the algorithm simple, we also never delete an incompletely
|
|
* split page (they should be rare enough that this doesn't make any
|
|
* meaningful difference to disk usage):
|
|
*
|
|
* The INCOMPLETE_SPLIT flag on the page tells us if the page is the
|
|
* left half of an incomplete split, but ensuring that it's not the
|
|
* right half is more complicated. For that, we have to check that
|
|
* the left sibling doesn't have its INCOMPLETE_SPLIT flag set. On
|
|
* the first iteration, we temporarily release the lock on the current
|
|
* page, and check the left sibling and also construct a search stack
|
|
* to. On subsequent iterations, we know we stepped right from a page
|
|
* that passed these tests, so it's OK.
|
|
*/
|
|
if (P_RIGHTMOST(opaque) || P_ISROOT(opaque) || P_ISDELETED(opaque) ||
|
|
P_FIRSTDATAKEY(opaque) <= PageGetMaxOffsetNumber(page) ||
|
|
P_INCOMPLETE_SPLIT(opaque))
|
|
{
|
|
/* Should never fail to delete a half-dead page */
|
|
Assert(!P_ISHALFDEAD(opaque));
|
|
|
|
_bt_relbuf(rel, buf);
|
|
return ndeleted;
|
|
}
|
|
|
|
/*
|
|
* First, remove downlink pointing to the page (or a parent of the
|
|
* page, if we are going to delete a taller branch), and mark the page
|
|
* as half-dead.
|
|
*/
|
|
if (!P_ISHALFDEAD(opaque))
|
|
{
|
|
/*
|
|
* We need an approximate pointer to the page's parent page. We
|
|
* use the standard search mechanism to search for the page's high
|
|
* key; this will give us a link to either the current parent or
|
|
* someplace to its left (if there are multiple equal high keys).
|
|
*
|
|
* Also check if this is the right-half of an incomplete split
|
|
* (see comment above).
|
|
*/
|
|
if (!stack)
|
|
{
|
|
ScanKey itup_scankey;
|
|
ItemId itemid;
|
|
IndexTuple targetkey;
|
|
Buffer lbuf;
|
|
BlockNumber leftsib;
|
|
|
|
itemid = PageGetItemId(page, P_HIKEY);
|
|
targetkey = CopyIndexTuple((IndexTuple) PageGetItem(page, itemid));
|
|
|
|
leftsib = opaque->btpo_prev;
|
|
|
|
/*
|
|
* To avoid deadlocks, we'd better drop the leaf page lock
|
|
* before going further.
|
|
*/
|
|
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
|
|
|
|
/*
|
|
* Fetch the left sibling, to check that it's not marked with
|
|
* INCOMPLETE_SPLIT flag. That would mean that the page
|
|
* to-be-deleted doesn't have a downlink, and the page
|
|
* deletion algorithm isn't prepared to handle that.
|
|
*/
|
|
if (!P_LEFTMOST(opaque))
|
|
{
|
|
BTPageOpaque lopaque;
|
|
Page lpage;
|
|
|
|
lbuf = _bt_getbuf(rel, leftsib, BT_READ);
|
|
lpage = BufferGetPage(lbuf);
|
|
lopaque = (BTPageOpaque) PageGetSpecialPointer(lpage);
|
|
|
|
/*
|
|
* If the left sibling is split again by another backend,
|
|
* after we released the lock, we know that the first
|
|
* split must have finished, because we don't allow an
|
|
* incompletely-split page to be split again. So we don't
|
|
* need to walk right here.
|
|
*/
|
|
if (lopaque->btpo_next == BufferGetBlockNumber(buf) &&
|
|
P_INCOMPLETE_SPLIT(lopaque))
|
|
{
|
|
ReleaseBuffer(buf);
|
|
_bt_relbuf(rel, lbuf);
|
|
return ndeleted;
|
|
}
|
|
_bt_relbuf(rel, lbuf);
|
|
}
|
|
|
|
/* we need an insertion scan key for the search, so build one */
|
|
itup_scankey = _bt_mkscankey(rel, targetkey);
|
|
/* find the leftmost leaf page containing this key */
|
|
stack = _bt_search(rel, rel->rd_rel->relnatts, itup_scankey,
|
|
false, &lbuf, BT_READ);
|
|
/* don't need a pin on the page */
|
|
_bt_relbuf(rel, lbuf);
|
|
|
|
/*
|
|
* Re-lock the leaf page, and start over, to re-check that the
|
|
* page can still be deleted.
|
|
*/
|
|
LockBuffer(buf, BT_WRITE);
|
|
continue;
|
|
}
|
|
|
|
if (!_bt_mark_page_halfdead(rel, buf, stack))
|
|
{
|
|
_bt_relbuf(rel, buf);
|
|
return ndeleted;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Then unlink it from its siblings. Each call to
|
|
* _bt_unlink_halfdead_page unlinks the topmost page from the branch,
|
|
* making it shallower. Iterate until the leaf page is gone.
|
|
*/
|
|
rightsib_empty = false;
|
|
while (P_ISHALFDEAD(opaque))
|
|
{
|
|
if (!_bt_unlink_halfdead_page(rel, buf, &rightsib_empty))
|
|
{
|
|
_bt_relbuf(rel, buf);
|
|
return ndeleted;
|
|
}
|
|
ndeleted++;
|
|
}
|
|
|
|
rightsib = opaque->btpo_next;
|
|
|
|
_bt_relbuf(rel, buf);
|
|
|
|
/*
|
|
* The page has now been deleted. If its right sibling is completely
|
|
* empty, it's possible that the reason we haven't deleted it earlier
|
|
* is that it was the rightmost child of the parent. Now that we
|
|
* removed the downlink for this page, the right sibling might now be
|
|
* the only child of the parent, and could be removed. It would be
|
|
* picked up by the next vacuum anyway, but might as well try to
|
|
* remove it now, so loop back to process the right sibling.
|
|
*/
|
|
if (!rightsib_empty)
|
|
break;
|
|
|
|
buf = _bt_getbuf(rel, rightsib, BT_WRITE);
|
|
}
|
|
|
|
return ndeleted;
|
|
}
|
|
|
|
/*
|
|
* First stage of page deletion. Remove the downlink to the top of the
|
|
* branch being deleted, and mark the leaf page as half-dead.
|
|
*/
|
|
static bool
|
|
_bt_mark_page_halfdead(Relation rel, Buffer leafbuf, BTStack stack)
|
|
{
|
|
BlockNumber leafblkno;
|
|
BlockNumber leafrightsib;
|
|
BlockNumber target;
|
|
BlockNumber rightsib;
|
|
ItemId itemid;
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
Buffer topparent;
|
|
OffsetNumber topoff;
|
|
OffsetNumber nextoffset;
|
|
IndexTuple itup;
|
|
IndexTupleData trunctuple;
|
|
|
|
page = BufferGetPage(leafbuf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
Assert(!P_RIGHTMOST(opaque) && !P_ISROOT(opaque) && !P_ISDELETED(opaque) &&
|
|
!P_ISHALFDEAD(opaque) && P_ISLEAF(opaque) &&
|
|
P_FIRSTDATAKEY(opaque) > PageGetMaxOffsetNumber(page));
|
|
|
|
/*
|
|
* Save info about the leaf page.
|
|
*/
|
|
leafblkno = BufferGetBlockNumber(leafbuf);
|
|
leafrightsib = opaque->btpo_next;
|
|
|
|
/*
|
|
* Before attempting to lock the parent page, check that the right sibling
|
|
* is not in half-dead state. A half-dead right sibling would have no
|
|
* downlink in the parent, which would be highly confusing later when we
|
|
* delete the downlink that follows the current page's downlink. (I
|
|
* believe the deletion would work correctly, but it would fail the
|
|
* cross-check we make that the following downlink points to the right
|
|
* sibling of the delete page.)
|
|
*/
|
|
if (_bt_is_page_halfdead(rel, leafrightsib))
|
|
{
|
|
elog(DEBUG1, "could not delete page %u because its right sibling %u is half-dead",
|
|
leafblkno, leafrightsib);
|
|
return false;
|
|
}
|
|
|
|
/*
|
|
* We cannot delete a page that is the rightmost child of its immediate
|
|
* parent, unless it is the only child --- in which case the parent has to
|
|
* be deleted too, and the same condition applies recursively to it. We
|
|
* have to check this condition all the way up before trying to delete,
|
|
* and lock the final parent of the to-be-deleted branch.
|
|
*/
|
|
rightsib = leafrightsib;
|
|
target = leafblkno;
|
|
if (!_bt_lock_branch_parent(rel, leafblkno, stack,
|
|
&topparent, &topoff, &target, &rightsib))
|
|
return false;
|
|
|
|
/*
|
|
* Check that the parent-page index items we're about to delete/overwrite
|
|
* contain what we expect. This can fail if the index has become corrupt
|
|
* for some reason. We want to throw any error before entering the
|
|
* critical section --- otherwise it'd be a PANIC.
|
|
*
|
|
* The test on the target item is just an Assert because
|
|
* _bt_lock_branch_parent should have guaranteed it has the expected
|
|
* contents. The test on the next-child downlink is known to sometimes
|
|
* fail in the field, though.
|
|
*/
|
|
page = BufferGetPage(topparent);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
#ifdef USE_ASSERT_CHECKING
|
|
itemid = PageGetItemId(page, topoff);
|
|
itup = (IndexTuple) PageGetItem(page, itemid);
|
|
Assert(ItemPointerGetBlockNumber(&(itup->t_tid)) == target);
|
|
#endif
|
|
|
|
nextoffset = OffsetNumberNext(topoff);
|
|
itemid = PageGetItemId(page, nextoffset);
|
|
itup = (IndexTuple) PageGetItem(page, itemid);
|
|
if (ItemPointerGetBlockNumber(&(itup->t_tid)) != rightsib)
|
|
elog(ERROR, "right sibling %u of block %u is not next child %u of block %u in index \"%s\"",
|
|
rightsib, target, ItemPointerGetBlockNumber(&(itup->t_tid)),
|
|
BufferGetBlockNumber(topparent), RelationGetRelationName(rel));
|
|
|
|
/*
|
|
* Any insert which would have gone on the leaf block will now go to its
|
|
* right sibling.
|
|
*/
|
|
PredicateLockPageCombine(rel, leafblkno, leafrightsib);
|
|
|
|
/* No ereport(ERROR) until changes are logged */
|
|
START_CRIT_SECTION();
|
|
|
|
/*
|
|
* Update parent. The normal case is a tad tricky because we want to
|
|
* delete the target's downlink and the *following* key. Easiest way is
|
|
* to copy the right sibling's downlink over the target downlink, and then
|
|
* delete the following item.
|
|
*/
|
|
page = BufferGetPage(topparent);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
itemid = PageGetItemId(page, topoff);
|
|
itup = (IndexTuple) PageGetItem(page, itemid);
|
|
ItemPointerSet(&(itup->t_tid), rightsib, P_HIKEY);
|
|
|
|
nextoffset = OffsetNumberNext(topoff);
|
|
PageIndexTupleDelete(page, nextoffset);
|
|
|
|
/*
|
|
* Mark the leaf page as half-dead, and stamp it with a pointer to the
|
|
* highest internal page in the branch we're deleting. We use the tid of
|
|
* the high key to store it.
|
|
*/
|
|
page = BufferGetPage(leafbuf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
opaque->btpo_flags |= BTP_HALF_DEAD;
|
|
|
|
PageIndexTupleDelete(page, P_HIKEY);
|
|
Assert(PageGetMaxOffsetNumber(page) == 0);
|
|
MemSet(&trunctuple, 0, sizeof(IndexTupleData));
|
|
trunctuple.t_info = sizeof(IndexTupleData);
|
|
if (target != leafblkno)
|
|
ItemPointerSet(&trunctuple.t_tid, target, 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");
|
|
|
|
/* Must mark buffers dirty before XLogInsert */
|
|
MarkBufferDirty(topparent);
|
|
MarkBufferDirty(leafbuf);
|
|
|
|
/* XLOG stuff */
|
|
if (RelationNeedsWAL(rel))
|
|
{
|
|
xl_btree_mark_page_halfdead xlrec;
|
|
XLogRecPtr recptr;
|
|
|
|
xlrec.poffset = topoff;
|
|
xlrec.leafblk = leafblkno;
|
|
if (target != leafblkno)
|
|
xlrec.topparent = target;
|
|
else
|
|
xlrec.topparent = InvalidBlockNumber;
|
|
|
|
XLogBeginInsert();
|
|
XLogRegisterBuffer(0, leafbuf, REGBUF_WILL_INIT);
|
|
XLogRegisterBuffer(1, topparent, REGBUF_STANDARD);
|
|
|
|
page = BufferGetPage(leafbuf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
xlrec.leftblk = opaque->btpo_prev;
|
|
xlrec.rightblk = opaque->btpo_next;
|
|
|
|
XLogRegisterData((char *) &xlrec, SizeOfBtreeMarkPageHalfDead);
|
|
|
|
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_MARK_PAGE_HALFDEAD);
|
|
|
|
page = BufferGetPage(topparent);
|
|
PageSetLSN(page, recptr);
|
|
page = BufferGetPage(leafbuf);
|
|
PageSetLSN(page, recptr);
|
|
}
|
|
|
|
END_CRIT_SECTION();
|
|
|
|
_bt_relbuf(rel, topparent);
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* Unlink a page in a branch of half-dead pages from its siblings.
|
|
*
|
|
* If the leaf page still has a downlink pointing to it, unlinks the highest
|
|
* parent in the to-be-deleted branch instead of the leaf page. To get rid
|
|
* of the whole branch, including the leaf page itself, iterate until the
|
|
* leaf page is deleted.
|
|
*
|
|
* Returns 'false' if the page could not be unlinked (shouldn't happen).
|
|
* If the (new) right sibling of the page is empty, *rightsib_empty is set
|
|
* to true.
|
|
*/
|
|
static bool
|
|
_bt_unlink_halfdead_page(Relation rel, Buffer leafbuf, bool *rightsib_empty)
|
|
{
|
|
BlockNumber leafblkno = BufferGetBlockNumber(leafbuf);
|
|
BlockNumber leafleftsib;
|
|
BlockNumber leafrightsib;
|
|
BlockNumber target;
|
|
BlockNumber leftsib;
|
|
BlockNumber rightsib;
|
|
Buffer lbuf = InvalidBuffer;
|
|
Buffer buf;
|
|
Buffer rbuf;
|
|
Buffer metabuf = InvalidBuffer;
|
|
Page metapg = NULL;
|
|
BTMetaPageData *metad = NULL;
|
|
ItemId itemid;
|
|
Page page;
|
|
BTPageOpaque opaque;
|
|
bool rightsib_is_rightmost;
|
|
int targetlevel;
|
|
ItemPointer leafhikey;
|
|
BlockNumber nextchild;
|
|
|
|
page = BufferGetPage(leafbuf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
Assert(P_ISLEAF(opaque) && P_ISHALFDEAD(opaque));
|
|
|
|
/*
|
|
* Remember some information about the leaf page.
|
|
*/
|
|
itemid = PageGetItemId(page, P_HIKEY);
|
|
leafhikey = &((IndexTuple) PageGetItem(page, itemid))->t_tid;
|
|
leafleftsib = opaque->btpo_prev;
|
|
leafrightsib = opaque->btpo_next;
|
|
|
|
LockBuffer(leafbuf, BUFFER_LOCK_UNLOCK);
|
|
|
|
/*
|
|
* If the leaf page still has a parent pointing to it (or a chain of
|
|
* parents), we don't unlink the leaf page yet, but the topmost remaining
|
|
* parent in the branch.
|
|
*/
|
|
if (ItemPointerIsValid(leafhikey))
|
|
{
|
|
target = ItemPointerGetBlockNumber(leafhikey);
|
|
|
|
/* fetch the block number of the topmost parent's left sibling */
|
|
buf = _bt_getbuf(rel, target, BT_READ);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
leftsib = opaque->btpo_prev;
|
|
targetlevel = opaque->btpo.level;
|
|
|
|
/*
|
|
* To avoid deadlocks, we'd better drop the target page lock before
|
|
* going further.
|
|
*/
|
|
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
|
|
}
|
|
else
|
|
{
|
|
target = leafblkno;
|
|
|
|
buf = leafbuf;
|
|
leftsib = opaque->btpo_prev;
|
|
targetlevel = 0;
|
|
}
|
|
|
|
/*
|
|
* We have to lock the pages we need to modify in the standard order:
|
|
* moving right, then up. Else we will deadlock against other writers.
|
|
*
|
|
* So, first lock the leaf page, if it's not the target. Then find and
|
|
* write-lock the current left sibling of the target page. The sibling
|
|
* that was current a moment ago could have split, so we may have to move
|
|
* right. This search could fail if either the sibling or the target page
|
|
* was deleted by someone else meanwhile; if so, give up. (Right now,
|
|
* that should never happen, since page deletion is only done in VACUUM
|
|
* and there shouldn't be multiple VACUUMs concurrently on the same
|
|
* table.)
|
|
*/
|
|
if (target != leafblkno)
|
|
LockBuffer(leafbuf, BT_WRITE);
|
|
if (leftsib != P_NONE)
|
|
{
|
|
lbuf = _bt_getbuf(rel, leftsib, BT_WRITE);
|
|
page = BufferGetPage(lbuf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
while (P_ISDELETED(opaque) || opaque->btpo_next != target)
|
|
{
|
|
/* step right one page */
|
|
leftsib = opaque->btpo_next;
|
|
_bt_relbuf(rel, lbuf);
|
|
if (leftsib == P_NONE)
|
|
{
|
|
elog(LOG, "no left sibling (concurrent deletion?) in \"%s\"",
|
|
RelationGetRelationName(rel));
|
|
return false;
|
|
}
|
|
lbuf = _bt_getbuf(rel, leftsib, BT_WRITE);
|
|
page = BufferGetPage(lbuf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
}
|
|
}
|
|
else
|
|
lbuf = InvalidBuffer;
|
|
|
|
/*
|
|
* Next write-lock the target page itself. It should be okay to take just
|
|
* a write lock not a superexclusive lock, since no scans would stop on an
|
|
* empty page.
|
|
*/
|
|
LockBuffer(buf, BT_WRITE);
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
|
|
/*
|
|
* Check page is still empty etc, else abandon deletion. This is just for
|
|
* paranoia's sake; a half-dead page cannot resurrect because there can be
|
|
* only one vacuum process running at a time.
|
|
*/
|
|
if (P_RIGHTMOST(opaque) || P_ISROOT(opaque) || P_ISDELETED(opaque))
|
|
{
|
|
elog(ERROR, "half-dead page changed status unexpectedly in block %u of index \"%s\"",
|
|
target, RelationGetRelationName(rel));
|
|
}
|
|
if (opaque->btpo_prev != leftsib)
|
|
elog(ERROR, "left link changed unexpectedly in block %u of index \"%s\"",
|
|
target, RelationGetRelationName(rel));
|
|
|
|
if (target == leafblkno)
|
|
{
|
|
if (P_FIRSTDATAKEY(opaque) <= PageGetMaxOffsetNumber(page) ||
|
|
!P_ISLEAF(opaque) || !P_ISHALFDEAD(opaque))
|
|
elog(ERROR, "half-dead page changed status unexpectedly in block %u of index \"%s\"",
|
|
target, RelationGetRelationName(rel));
|
|
nextchild = InvalidBlockNumber;
|
|
}
|
|
else
|
|
{
|
|
if (P_FIRSTDATAKEY(opaque) != PageGetMaxOffsetNumber(page) ||
|
|
P_ISLEAF(opaque))
|
|
elog(ERROR, "half-dead page changed status unexpectedly in block %u of index \"%s\"",
|
|
target, RelationGetRelationName(rel));
|
|
|
|
/* remember the next non-leaf child down in the branch. */
|
|
itemid = PageGetItemId(page, P_FIRSTDATAKEY(opaque));
|
|
nextchild = ItemPointerGetBlockNumber(&((IndexTuple) PageGetItem(page, itemid))->t_tid);
|
|
if (nextchild == leafblkno)
|
|
nextchild = InvalidBlockNumber;
|
|
}
|
|
|
|
/*
|
|
* And next write-lock the (current) right sibling.
|
|
*/
|
|
rightsib = opaque->btpo_next;
|
|
rbuf = _bt_getbuf(rel, rightsib, BT_WRITE);
|
|
page = BufferGetPage(rbuf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
if (opaque->btpo_prev != target)
|
|
elog(ERROR, "right sibling's left-link doesn't match: "
|
|
"block %u links to %u instead of expected %u in index \"%s\"",
|
|
rightsib, opaque->btpo_prev, target,
|
|
RelationGetRelationName(rel));
|
|
rightsib_is_rightmost = P_RIGHTMOST(opaque);
|
|
*rightsib_empty = (P_FIRSTDATAKEY(opaque) > PageGetMaxOffsetNumber(page));
|
|
|
|
/*
|
|
* If we are deleting the next-to-last page on the target's level, then
|
|
* the rightsib is a candidate to become the new fast root. (In theory, it
|
|
* might be possible to push the fast root even further down, but the odds
|
|
* of doing so are slim, and the locking considerations daunting.)
|
|
*
|
|
* We don't support handling this in the case where the parent is becoming
|
|
* half-dead, even though it theoretically could occur.
|
|
*
|
|
* We can safely acquire a lock on the metapage here --- see comments for
|
|
* _bt_newroot().
|
|
*/
|
|
if (leftsib == P_NONE && rightsib_is_rightmost)
|
|
{
|
|
page = BufferGetPage(rbuf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
if (P_RIGHTMOST(opaque))
|
|
{
|
|
/* rightsib will be the only one left on the level */
|
|
metabuf = _bt_getbuf(rel, BTREE_METAPAGE, BT_WRITE);
|
|
metapg = BufferGetPage(metabuf);
|
|
metad = BTPageGetMeta(metapg);
|
|
|
|
/*
|
|
* The expected case here is btm_fastlevel == targetlevel+1; if
|
|
* the fastlevel is <= targetlevel, something is wrong, and we
|
|
* choose to overwrite it to fix it.
|
|
*/
|
|
if (metad->btm_fastlevel > targetlevel + 1)
|
|
{
|
|
/* no update wanted */
|
|
_bt_relbuf(rel, metabuf);
|
|
metabuf = InvalidBuffer;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Here we begin doing the deletion.
|
|
*/
|
|
|
|
/* No ereport(ERROR) until changes are logged */
|
|
START_CRIT_SECTION();
|
|
|
|
/*
|
|
* Update siblings' side-links. Note the target page's side-links will
|
|
* continue to point to the siblings. Asserts here are just rechecking
|
|
* things we already verified above.
|
|
*/
|
|
if (BufferIsValid(lbuf))
|
|
{
|
|
page = BufferGetPage(lbuf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
Assert(opaque->btpo_next == target);
|
|
opaque->btpo_next = rightsib;
|
|
}
|
|
page = BufferGetPage(rbuf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
Assert(opaque->btpo_prev == target);
|
|
opaque->btpo_prev = leftsib;
|
|
|
|
/*
|
|
* 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 (target != leafblkno)
|
|
{
|
|
if (nextchild == InvalidBlockNumber)
|
|
ItemPointerSetInvalid(leafhikey);
|
|
else
|
|
ItemPointerSet(leafhikey, nextchild, P_HIKEY);
|
|
}
|
|
|
|
/*
|
|
* Mark the page itself deleted. It can be recycled when all current
|
|
* transactions are gone. Storing GetTopTransactionId() would work, but
|
|
* we're in VACUUM and would not otherwise have an XID. Having already
|
|
* updated links to the target, ReadNewTransactionId() suffices as an
|
|
* upper bound. Any scan having retained a now-stale link is advertising
|
|
* in its PGXACT an xmin less than or equal to the value we read here. It
|
|
* will continue to do so, holding back RecentGlobalXmin, for the duration
|
|
* of that scan.
|
|
*/
|
|
page = BufferGetPage(buf);
|
|
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
|
|
opaque->btpo_flags &= ~BTP_HALF_DEAD;
|
|
opaque->btpo_flags |= BTP_DELETED;
|
|
opaque->btpo.xact = ReadNewTransactionId();
|
|
|
|
/* And update the metapage, if needed */
|
|
if (BufferIsValid(metabuf))
|
|
{
|
|
metad->btm_fastroot = rightsib;
|
|
metad->btm_fastlevel = targetlevel;
|
|
MarkBufferDirty(metabuf);
|
|
}
|
|
|
|
/* Must mark buffers dirty before XLogInsert */
|
|
MarkBufferDirty(rbuf);
|
|
MarkBufferDirty(buf);
|
|
if (BufferIsValid(lbuf))
|
|
MarkBufferDirty(lbuf);
|
|
if (target != leafblkno)
|
|
MarkBufferDirty(leafbuf);
|
|
|
|
/* XLOG stuff */
|
|
if (RelationNeedsWAL(rel))
|
|
{
|
|
xl_btree_unlink_page xlrec;
|
|
xl_btree_metadata xlmeta;
|
|
uint8 xlinfo;
|
|
XLogRecPtr recptr;
|
|
|
|
XLogBeginInsert();
|
|
|
|
XLogRegisterBuffer(0, buf, REGBUF_WILL_INIT);
|
|
if (BufferIsValid(lbuf))
|
|
XLogRegisterBuffer(1, lbuf, REGBUF_STANDARD);
|
|
XLogRegisterBuffer(2, rbuf, REGBUF_STANDARD);
|
|
if (target != leafblkno)
|
|
XLogRegisterBuffer(3, leafbuf, REGBUF_WILL_INIT);
|
|
|
|
/* information on the unlinked block */
|
|
xlrec.leftsib = leftsib;
|
|
xlrec.rightsib = rightsib;
|
|
xlrec.btpo_xact = opaque->btpo.xact;
|
|
|
|
/* information needed to recreate the leaf block (if not the target) */
|
|
xlrec.leafleftsib = leafleftsib;
|
|
xlrec.leafrightsib = leafrightsib;
|
|
xlrec.topparent = nextchild;
|
|
|
|
XLogRegisterData((char *) &xlrec, SizeOfBtreeUnlinkPage);
|
|
|
|
if (BufferIsValid(metabuf))
|
|
{
|
|
XLogRegisterBuffer(4, metabuf, REGBUF_WILL_INIT);
|
|
|
|
xlmeta.root = metad->btm_root;
|
|
xlmeta.level = metad->btm_level;
|
|
xlmeta.fastroot = metad->btm_fastroot;
|
|
xlmeta.fastlevel = metad->btm_fastlevel;
|
|
|
|
XLogRegisterBufData(4, (char *) &xlmeta, sizeof(xl_btree_metadata));
|
|
xlinfo = XLOG_BTREE_UNLINK_PAGE_META;
|
|
}
|
|
else
|
|
xlinfo = XLOG_BTREE_UNLINK_PAGE;
|
|
|
|
recptr = XLogInsert(RM_BTREE_ID, xlinfo);
|
|
|
|
if (BufferIsValid(metabuf))
|
|
{
|
|
PageSetLSN(metapg, recptr);
|
|
}
|
|
page = BufferGetPage(rbuf);
|
|
PageSetLSN(page, recptr);
|
|
page = BufferGetPage(buf);
|
|
PageSetLSN(page, recptr);
|
|
if (BufferIsValid(lbuf))
|
|
{
|
|
page = BufferGetPage(lbuf);
|
|
PageSetLSN(page, recptr);
|
|
}
|
|
if (target != leafblkno)
|
|
{
|
|
page = BufferGetPage(leafbuf);
|
|
PageSetLSN(page, recptr);
|
|
}
|
|
}
|
|
|
|
END_CRIT_SECTION();
|
|
|
|
/* release metapage */
|
|
if (BufferIsValid(metabuf))
|
|
_bt_relbuf(rel, metabuf);
|
|
|
|
/* release siblings */
|
|
if (BufferIsValid(lbuf))
|
|
_bt_relbuf(rel, lbuf);
|
|
_bt_relbuf(rel, rbuf);
|
|
|
|
/*
|
|
* Release the target, if it was not the leaf block. The leaf is always
|
|
* kept locked.
|
|
*/
|
|
if (target != leafblkno)
|
|
_bt_relbuf(rel, buf);
|
|
|
|
return true;
|
|
}
|