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gist.c
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/*-------------------------------------------------------------------------
*
* gist.c
* interface routines for the postgres GiST index access method.
*
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/access/gist/gist.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "gist_private.h"
#include "gistscan.h"
#include "catalog/pg_collation.h"
#include "miscadmin.h"
#include "storage/lmgr.h"
#include "storage/predicate.h"
#include "nodes/execnodes.h"
#include "utils/builtins.h"
#include "utils/index_selfuncs.h"
#include "utils/memutils.h"
#include "utils/rel.h"
/* non-export function prototypes */
static void gistfixsplit(GISTInsertState *state, GISTSTATE *giststate);
static bool gistinserttuple(GISTInsertState *state, GISTInsertStack *stack,
GISTSTATE *giststate, IndexTuple tuple, OffsetNumber oldoffnum);
static bool gistinserttuples(GISTInsertState *state, GISTInsertStack *stack,
GISTSTATE *giststate,
IndexTuple *tuples, int ntup, OffsetNumber oldoffnum,
Buffer leftchild, Buffer rightchild,
bool unlockbuf, bool unlockleftchild, int ndeltup, OffsetNumber skipoffnum);
static void gistfinishsplit(GISTInsertState *state, GISTInsertStack *stack,
GISTSTATE *giststate, List *splitinfo, bool releasebuf);
static void gistprunepage(Relation rel, Page page, Buffer buffer,
Relation heapRel);
#define ROTATEDIST(d) do { \
SplitedPageLayout *tmp=(SplitedPageLayout*)palloc0(sizeof(SplitedPageLayout)); \
tmp->block.blkno = InvalidBlockNumber; \
tmp->buffer = InvalidBuffer; \
tmp->next = (d); \
(d)=tmp; \
} while(0)
PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(agshandler);
/*
* GiST handler function: return IndexAmRoutine with access method parameters
* and callbacks.
*/
Datum
agshandler(PG_FUNCTION_ARGS)
{
IndexAmRoutine *amroutine = makeNode(IndexAmRoutine);
amroutine->amstrategies = 0;
amroutine->amsupport = GISTNProcs;
amroutine->amcanorder = false;
amroutine->amcanorderbyop = true;
amroutine->amcanbackward = false;
amroutine->amcanunique = false;
amroutine->amcanmulticol = true;
amroutine->amoptionalkey = true;
amroutine->amsearcharray = false;
amroutine->amsearchnulls = true;
amroutine->amstorage = true;
amroutine->amclusterable = true;
amroutine->ampredlocks = true;
amroutine->amcanparallel = false;
amroutine->amcaninclude = true;
amroutine->amkeytype = InvalidOid;
amroutine->ambuild = gistbuild;
amroutine->ambuildempty = gistbuildempty;
amroutine->aminsert = gistinsert;
amroutine->ambulkdelete = gistbulkdelete;
amroutine->amvacuumcleanup = gistvacuumcleanup;
amroutine->amcanreturn = gistcanreturn;
amroutine->amcostestimate = gistcostestimate;
amroutine->amoptions = gistoptions;
amroutine->amproperty = gistproperty;
amroutine->ambuildphasename = NULL;
amroutine->amvalidate = gistvalidate;
amroutine->ambeginscan = gistbeginscan;
amroutine->amrescan = gistrescan;
amroutine->amgettuple = gistgettuple;
amroutine->amgetbitmap = gistgetbitmap;
amroutine->amendscan = gistendscan;
amroutine->ammarkpos = NULL;
amroutine->amrestrpos = NULL;
amroutine->amestimateparallelscan = NULL;
amroutine->aminitparallelscan = NULL;
amroutine->amparallelrescan = NULL;
PG_RETURN_POINTER(amroutine);
}
/*
* Create and return a temporary memory context for use by GiST. We
* _always_ invoke user-provided methods in a temporary memory
* context, so that memory leaks in those functions cannot cause
* problems. Also, we use some additional temporary contexts in the
* GiST code itself, to avoid the need to do some awkward manual
* memory management.
*/
MemoryContext
createTempGistContext(void)
{
return AllocSetContextCreate(CurrentMemoryContext,
"GiST temporary context",
ALLOCSET_DEFAULT_SIZES);
}
/*
* gistbuildempty() -- build an empty gist index in the initialization fork
*/
void
gistbuildempty(Relation index)
{
Buffer buffer;
/* Initialize the root page */
buffer = ReadBufferExtended(index, INIT_FORKNUM, P_NEW, RBM_NORMAL, NULL);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
/* Initialize and xlog buffer */
START_CRIT_SECTION();
GISTInitBuffer(buffer, F_LEAF);
MarkBufferDirty(buffer);
log_newpage_buffer(buffer, true);
END_CRIT_SECTION();
/* Unlock and release the buffer */
UnlockReleaseBuffer(buffer);
}
/*
* gistinsert -- wrapper for GiST tuple insertion.
*
* This is the public interface routine for tuple insertion in GiSTs.
* It doesn't do any work; just locks the relation and passes the buck.
*/
bool
gistinsert(Relation r, Datum *values, bool *isnull,
ItemPointer ht_ctid, Relation heapRel,
IndexUniqueCheck checkUnique,
IndexInfo *indexInfo)
{
GISTSTATE *giststate = (GISTSTATE *) indexInfo->ii_AmCache;
IndexTuple itup;
MemoryContext oldCxt;
/* Initialize GISTSTATE cache if first call in this statement */
if (giststate == NULL)
{
oldCxt = MemoryContextSwitchTo(indexInfo->ii_Context);
giststate = initGISTstate(r);
giststate->tempCxt = createTempGistContext();
indexInfo->ii_AmCache = (void *) giststate;
MemoryContextSwitchTo(oldCxt);
}
oldCxt = MemoryContextSwitchTo(giststate->tempCxt);
itup = gistFormTuple(giststate, r,
values, isnull, true /* size is currently bogus */ );
itup->t_tid = *ht_ctid;
gistdoinsert(r, itup, 0, giststate, heapRel, false);
/* cleanup */
MemoryContextSwitchTo(oldCxt);
MemoryContextReset(giststate->tempCxt);
return false;
}
/*
* Place tuples from 'itup' to 'buffer'. If 'oldoffnum' is valid, the tuple
* at that offset is atomically removed along with inserting the new tuples.
* This is used to replace a tuple with a new one.
*
* If 'leftchildbuf' is valid, we're inserting the downlink for the page
* to the right of 'leftchildbuf', or updating the downlink for 'leftchildbuf'.
* F_FOLLOW_RIGHT flag on 'leftchildbuf' is cleared and NSN is set.
*
* If 'markfollowright' is true and the page is split, the left child is
* marked with F_FOLLOW_RIGHT flag. That is the normal case. During buffered
* index build, however, there is no concurrent access and the page splitting
* is done in a slightly simpler fashion, and false is passed.
*
* If there is not enough room on the page, it is split. All the split
* pages are kept pinned and locked and returned in *splitinfo, the caller
* is responsible for inserting the downlinks for them. However, if
* 'buffer' is the root page and it needs to be split, gistplacetopage()
* performs the split as one atomic operation, and *splitinfo is set to NIL.
* In that case, we continue to hold the root page locked, and the child
* pages are released; note that new tuple(s) are *not* on the root page
* but in one of the new child pages.
*
* If 'newblkno' is not NULL, returns the block number of page the first
* new/updated tuple was inserted to. Usually it's the given page, but could
* be its right sibling if the page was split.
*
* Returns 'true' if the page was split, 'false' otherwise.
*/
bool
gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
Buffer buffer,
IndexTuple *itup, int ntup, OffsetNumber oldoffnum,
BlockNumber *newblkno,
Buffer leftchildbuf,
List **splitinfo,
bool markfollowright,
Relation heapRel,
bool is_build,
int ndeltup,
OffsetNumber skipoffnum)
{
BlockNumber blkno = BufferGetBlockNumber(buffer);
Page page = BufferGetPage(buffer);
bool is_leaf = (GistPageIsLeaf(page)) ? true : false;
XLogRecPtr recptr;
int i;
bool is_split;
/*
* Refuse to modify a page that's incompletely split. This should not
* happen because we finish any incomplete splits while we walk down the
* tree. However, it's remotely possible that another concurrent inserter
* splits a parent page, and errors out before completing the split. We
* will just throw an error in that case, and leave any split we had in
* progress unfinished too. The next insert that comes along will clean up
* the mess.
*/
if (GistFollowRight(page))
elog(ERROR, "concurrent GiST page split was incomplete");
*splitinfo = NIL;
/*
* if isupdate, remove old key: This node's key has been modified, either
* because a child split occurred or because we needed to adjust our key
* for an insert in a child node. Therefore, remove the old version of
* this node's key.
*
* for WAL replay, in the non-split case we handle this by setting up a
* one-element todelete array; in the split case, it's handled implicitly
* because the tuple vector passed to gistSplit won't include this tuple.
*/
is_split = gistnospace(page, itup, ntup, oldoffnum, freespace, ndeltup);
/*
* If leaf page is full, try at first to delete dead tuples. And then
* check again.
*/
if (is_split && GistPageIsLeaf(page) && GistPageHasGarbage(page))
{
gistprunepage(rel, page, buffer, heapRel);
is_split = gistnospace(page, itup, ntup, oldoffnum, freespace, ndeltup);
}
if (is_split)
{
/* no space for insertion */
IndexTuple *itvec;
int tlen;
SplitedPageLayout *dist = NULL,
*ptr;
BlockNumber oldrlink = InvalidBlockNumber;
GistNSN oldnsn = 0;
SplitedPageLayout rootpg;
bool is_rootsplit;
int npage;
is_rootsplit = (blkno == GIST_ROOT_BLKNO);
/*
* Form index tuples vector to split. If we're replacing an old tuple,
* remove the old version from the vector.
*/
itvec = gistextractpage(page, &tlen);
if (OffsetNumberIsValid(skipoffnum))
{
IndexTuple skiptuple = itvec[skipoffnum - FirstOffsetNumber];
int newskipgroupsize = GistTupleGetSkipCount(skiptuple) + ntup - ndeltup;
Assert(GistTupleIsSkip(skiptuple));
Assert(skipoffnum + newskipgroupsize <= PageGetMaxOffsetNumber(page) + ntup - ndeltup);
GistTupleSetSkipCount(skiptuple, newskipgroupsize);
}
if (OffsetNumberIsValid(oldoffnum) && ndeltup)
{
/* on inner page we should remove old tuples */
int pos = oldoffnum - FirstOffsetNumber;
tlen -= ndeltup;
if (pos != tlen)
memmove(itvec + pos, itvec + pos + ndeltup, sizeof(IndexTuple) * (tlen - pos));
}
itvec = gistjoinvector(itvec, &tlen, itup, ntup, oldoffnum);
if (GistTupleIsSkip(*itvec))
{
dist = gistSplitBySkipgroup(rel, page, itvec, tlen, giststate);
}
if (dist == NULL)
{
gistfiltervector(itvec, &tlen);
dist = gistSplit(rel, page, itvec, tlen, giststate);
}
/*
* Check that split didn't produce too many pages.
*/
npage = 0;
for (ptr = dist; ptr; ptr = ptr->next)
npage++;
/* in a root split, we'll add one more page to the list below */
if (is_rootsplit)
npage++;
if (npage > GIST_MAX_SPLIT_PAGES)
elog(ERROR, "GiST page split into too many halves (%d, maximum %d)",
npage, GIST_MAX_SPLIT_PAGES);
/*
* Set up pages to work with. Allocate new buffers for all but the
* leftmost page. The original page becomes the new leftmost page, and
* is just replaced with the new contents.
*
* For a root-split, allocate new buffers for all child pages, the
* original page is overwritten with new root page containing
* downlinks to the new child pages.
*/
ptr = dist;
if (!is_rootsplit)
{
/* save old rightlink and NSN */
oldrlink = GistPageGetOpaque(page)->rightlink;
oldnsn = GistPageGetNSN(page);
dist->buffer = buffer;
dist->block.blkno = BufferGetBlockNumber(buffer);
dist->page = PageGetTempPageCopySpecial(BufferGetPage(buffer));
/* clean all flags except F_LEAF */
GistPageGetOpaque(dist->page)->flags = (is_leaf) ? F_LEAF : 0;
ptr = ptr->next;
}
for (; ptr; ptr = ptr->next)
{
/* Allocate new page */
ptr->buffer = gistNewBuffer(rel);
GISTInitBuffer(ptr->buffer, (is_leaf) ? F_LEAF : 0);
ptr->page = BufferGetPage(ptr->buffer);
ptr->block.blkno = BufferGetBlockNumber(ptr->buffer);
PredicateLockPageSplit(rel,
BufferGetBlockNumber(buffer),
BufferGetBlockNumber(ptr->buffer));
}
/*
* Now that we know which blocks the new pages go to, set up downlink
* tuples to point to them.
*/
for (ptr = dist; ptr; ptr = ptr->next)
{
ItemPointerSetBlockNumber(&(ptr->itup->t_tid), ptr->block.blkno);
GistTupleSetValid(ptr->itup);
}
/*
* If this is a root split, we construct the new root page with the
* downlinks here directly, instead of requiring the caller to insert
* them. Add the new root page to the list along with the child pages.
*/
if (is_rootsplit)
{
IndexTuple *downlinks;
int ndownlinks = 1;
int i;
rootpg.buffer = buffer;
rootpg.page = PageGetTempPageCopySpecial(BufferGetPage(rootpg.buffer));
GistPageGetOpaque(rootpg.page)->flags = 0;
/* Prepare a vector of all the downlinks */
for (ptr = dist; ptr; ptr = ptr->next)
ndownlinks++;
downlinks = palloc(sizeof(IndexTuple) * ndownlinks);
for (i = 1, ptr = dist; ptr; ptr = ptr->next)
downlinks[i++] = ptr->itup;
downlinks[0] = gistunion(rel,downlinks + 1, ndownlinks - 1, giststate);
GistTupleMakeSkip(downlinks[0]);
GistTupleSetSkipCount(downlinks[0], ndownlinks - 1);
rootpg.block.blkno = GIST_ROOT_BLKNO;
rootpg.block.num = ndownlinks;
rootpg.list = gistfillitupvec(downlinks, ndownlinks,
&(rootpg.lenlist));
rootpg.itup = NULL;
rootpg.next = dist;
dist = &rootpg;
}
else
{
/* Prepare split-info to be returned to caller */
for (ptr = dist; ptr; ptr = ptr->next)
{
GISTPageSplitInfo *si = palloc(sizeof(GISTPageSplitInfo));
si->buf = ptr->buffer;
si->downlink = ptr->itup;
*splitinfo = lappend(*splitinfo, si);
}
}
/*
* Fill all pages. All the pages are new, ie. freshly allocated empty
* pages, or a temporary copy of the old page.
*/
for (ptr = dist; ptr; ptr = ptr->next)
{
char *data = (char *) (ptr->list);
for (i = 0; i < ptr->block.num; i++)
{
IndexTuple thistup = (IndexTuple) data;
if (PageAddItem(ptr->page, (Item) data, IndexTupleSize(thistup), i + FirstOffsetNumber, false, false) == InvalidOffsetNumber)
elog(ERROR, "failed to add item to index page in \"%s\"", RelationGetRelationName(rel));
/*
* If this is the first inserted/updated tuple, let the caller
* know which page it landed on.
*/
if (newblkno && ItemPointerEquals(&thistup->t_tid, &(*itup)->t_tid))
*newblkno = ptr->block.blkno;
data += IndexTupleSize(thistup);
}
/* Set up rightlinks */
if (ptr->next && ptr->block.blkno != GIST_ROOT_BLKNO)
GistPageGetOpaque(ptr->page)->rightlink =
ptr->next->block.blkno;
else
GistPageGetOpaque(ptr->page)->rightlink = oldrlink;
/*
* Mark the all but the right-most page with the follow-right
* flag. It will be cleared as soon as the downlink is inserted
* into the parent, but this ensures that if we error out before
* that, the index is still consistent. (in buffering build mode,
* any error will abort the index build anyway, so this is not
* needed.)
*/
if (ptr->next && !is_rootsplit && markfollowright)
GistMarkFollowRight(ptr->page);
else
GistClearFollowRight(ptr->page);
/*
* Copy the NSN of the original page to all pages. The
* F_FOLLOW_RIGHT flags ensure that scans will follow the
* rightlinks until the downlinks are inserted.
*/
GistPageSetNSN(ptr->page, oldnsn);
}
/*
* gistXLogSplit() needs to WAL log a lot of pages, prepare WAL
* insertion for that. NB: The number of pages and data segments
* specified here must match the calculations in gistXLogSplit()!
*/
if (!is_build && RelationNeedsWAL(rel))
XLogEnsureRecordSpace(npage, 1 + npage * 2);
START_CRIT_SECTION();
/*
* Must mark buffers dirty before XLogInsert, even though we'll still
* be changing their opaque fields below.
*/
for (ptr = dist; ptr; ptr = ptr->next)
MarkBufferDirty(ptr->buffer);
if (BufferIsValid(leftchildbuf))
MarkBufferDirty(leftchildbuf);
/*
* The first page in the chain was a temporary working copy meant to
* replace the old page. Copy it over the old page.
*/
PageRestoreTempPage(dist->page, BufferGetPage(dist->buffer));
dist->page = BufferGetPage(dist->buffer);
/*
* Write the WAL record.
*
* If we're building a new index, however, we don't WAL-log changes
* yet. The LSN-NSN interlock between parent and child requires that
* LSNs never move backwards, so set the LSNs to a value that's
* smaller than any real or fake unlogged LSN that might be generated
* later. (There can't be any concurrent scans during index build, so
* we don't need to be able to detect concurrent splits yet.)
*/
if (is_build)
recptr = GistBuildLSN;
else
{
if (RelationNeedsWAL(rel))
recptr = gistXLogSplit(is_leaf,
dist, oldrlink, oldnsn, leftchildbuf,
markfollowright);
else
recptr = gistGetFakeLSN(rel);
}
for (ptr = dist; ptr; ptr = ptr->next)
PageSetLSN(ptr->page, recptr);
/*
* Return the new child buffers to the caller.
*
* If this was a root split, we've already inserted the downlink
* pointers, in the form of a new root page. Therefore we can release
* all the new buffers, and keep just the root page locked.
*/
if (is_rootsplit)
{
for (ptr = dist->next; ptr; ptr = ptr->next)
UnlockReleaseBuffer(ptr->buffer);
}
}
else
{
/*
* Enough space. We always get here if ntup==0.
*/
START_CRIT_SECTION();
if (OffsetNumberIsValid(skipoffnum))
{
IndexTuple skiptuple = (IndexTuple) PageGetItem(page, PageGetItemId(page, skipoffnum));
int newskipgroupsize = GistTupleGetSkipCount(skiptuple) + ntup - ndeltup;
Assert(GistTupleIsSkip(skiptuple));
Assert(skipoffnum + newskipgroupsize <= PageGetMaxOffsetNumber(page) + ntup - ndeltup);
GistTupleSetSkipCount(skiptuple, newskipgroupsize);
}
/*
* Delete old tuple if any, then insert new tuple(s) if any. If
* possible, use the fast path of PageIndexTupleOverwrite.
*/
if (OffsetNumberIsValid(oldoffnum))
{
int noverwrite = Min(ntup,ndeltup);
for (i = 0; i < noverwrite; i++)
{
if (!PageIndexTupleOverwrite(page, oldoffnum + i, (Item) itup[i],
IndexTupleSize(itup[i])))
elog(ERROR, "failed to add item to index page in \"%s\"",
RelationGetRelationName(rel));
}
for (i = noverwrite; i < ndeltup; i++)
{
PageIndexTupleDelete(page, oldoffnum + i);
}
gistfillbuffer(page, itup + noverwrite, ntup - noverwrite, oldoffnum + noverwrite);
}
else
{
/* Just append new tuples at the end of the page */
gistfillbuffer(page, itup, ntup, InvalidOffsetNumber);
}
MarkBufferDirty(buffer);
if (BufferIsValid(leftchildbuf))
MarkBufferDirty(leftchildbuf);
if (is_build)
recptr = GistBuildLSN;
else
{
if (RelationNeedsWAL(rel))
{
OffsetNumber ndeloffs = 0,
deloffs[BLCKSZ /sizeof(ItemIdData)];
if (OffsetNumberIsValid(oldoffnum))
{
for (i = 0; i < ndeltup; i++)
deloffs[i] = oldoffnum + i;
ndeloffs = ndeltup;
}
recptr = gistXLogUpdate(buffer,
deloffs, ndeloffs, itup, ntup,
leftchildbuf, skipoffnum);
}
else
recptr = gistGetFakeLSN(rel);
}
PageSetLSN(page, recptr);
if (newblkno)
*newblkno = blkno;
}
/*
* If we inserted the downlink for a child page, set NSN and clear
* F_FOLLOW_RIGHT flag on the left child, so that concurrent scans know to
* follow the rightlink if and only if they looked at the parent page
* before we inserted the downlink.
*
* Note that we do this *after* writing the WAL record. That means that
* the possible full page image in the WAL record does not include these
* changes, and they must be replayed even if the page is restored from
* the full page image. There's a chicken-and-egg problem: if we updated
* the child pages first, we wouldn't know the recptr of the WAL record
* we're about to write.
*/
if (BufferIsValid(leftchildbuf))
{
Page leftpg = BufferGetPage(leftchildbuf);
GistPageSetNSN(leftpg, recptr);
GistClearFollowRight(leftpg);
PageSetLSN(leftpg, recptr);
}
END_CRIT_SECTION();
return is_split;
}
/*
* Workhouse routine for doing insertion into a GiST index. Note that
* this routine assumes it is invoked in a short-lived memory context,
* so it does not bother releasing palloc'd allocations.
*/
void
gistdoinsert(Relation r, IndexTuple itup, Size freespace,
GISTSTATE *giststate, Relation heapRel, bool is_build)
{
ItemId iid;
IndexTuple idxtuple;
GISTInsertStack firststack;
GISTInsertStack *stack;
GISTInsertState state;
bool xlocked = false;
memset(&state, 0, sizeof(GISTInsertState));
state.freespace = freespace;
state.r = r;
state.heapRel = heapRel;
state.is_build = is_build;
/* Start from the root */
firststack.blkno = GIST_ROOT_BLKNO;
firststack.lsn = 0;
firststack.parent = NULL;
firststack.downlinkoffnum = InvalidOffsetNumber;
state.stack = stack = &firststack;
/*
* Walk down along the path of smallest penalty, updating the parent
* pointers with the key we're inserting as we go. If we crash in the
* middle, the tree is consistent, although the possible parent updates
* were a waste.
*/
for (;;)
{
if (XLogRecPtrIsInvalid(stack->lsn))
stack->buffer = ReadBuffer(state.r, stack->blkno);
/*
* Be optimistic and grab shared lock first. Swap it for an exclusive
* lock later if we need to update the page.
*/
if (!xlocked)
{
LockBuffer(stack->buffer, GIST_SHARE);
gistcheckpage(state.r, stack->buffer);
}
stack->page = (Page) BufferGetPage(stack->buffer);
stack->lsn = xlocked ?
PageGetLSN(stack->page) : BufferGetLSNAtomic(stack->buffer);
Assert(!RelationNeedsWAL(state.r) || !XLogRecPtrIsInvalid(stack->lsn));
/*
* If this page was split but the downlink was never inserted to the
* parent because the inserting backend crashed before doing that, fix
* that now.
*/
if (GistFollowRight(stack->page))
{
if (!xlocked)
{
LockBuffer(stack->buffer, GIST_UNLOCK);
LockBuffer(stack->buffer, GIST_EXCLUSIVE);
xlocked = true;
/* someone might've completed the split when we unlocked */
if (!GistFollowRight(stack->page))
continue;
}
gistfixsplit(&state, giststate);
UnlockReleaseBuffer(stack->buffer);
xlocked = false;
state.stack = stack = stack->parent;
continue;
}
if (stack->blkno != GIST_ROOT_BLKNO &&
stack->parent->lsn < GistPageGetNSN(stack->page))
{
/*
* Concurrent split detected. There's no guarantee that the
* downlink for this page is consistent with the tuple we're
* inserting anymore, so go back to parent and rechoose the best
* child.
*/
UnlockReleaseBuffer(stack->buffer);
xlocked = false;
state.stack = stack = stack->parent;
continue;
}
if (!GistPageIsLeaf(stack->page))
{
OffsetNumber skipoffnum;
/*
* This is an internal page so continue to walk down the tree.
* Find the child node that has the minimum insertion penalty.
*/
BlockNumber childblkno;
IndexTuple newtup;
GISTInsertStack *item;
OffsetNumber downlinkoffnum;
/* currently, internal pages are never deleted */
Assert(!GistPageIsDeleted(stack->page));
downlinkoffnum = gistchoose(state.r, stack->page, itup, giststate, &skipoffnum);
if (OffsetNumberIsValid(skipoffnum))
{
iid = PageGetItemId(stack->page, skipoffnum);
idxtuple = (IndexTuple) PageGetItem(stack->page, iid);
Assert(GistTupleIsSkip(idxtuple));
/*
* Check that the key representing the target child node is
* consistent with the key we're inserting. Update it if it's not.
*/
newtup = gistgetadjusted(state.r, idxtuple, itup, giststate);
if (newtup)
{
/*
* Swap shared lock for an exclusive one. Beware, the page may
* change while we unlock/lock the page...
*/
if (!xlocked)
{
LockBuffer(stack->buffer, GIST_UNLOCK);
LockBuffer(stack->buffer, GIST_EXCLUSIVE);
xlocked = true;
stack->page = (Page) BufferGetPage(stack->buffer);
if (PageGetLSN(stack->page) != stack->lsn)
{
/* the page was changed while we unlocked it, retry */
continue;
}
}
/*
* Update the tuple.
*
* We still hold the lock after gistinserttuple(), but it
* might have to split the page to make the updated tuple fit.
* In that case the updated tuple might migrate to the other
* half of the split, so we have to go back to the parent and
* descend back to the half that's a better fit for the new
* tuple.
*/
if (gistinserttuple(&state, stack, giststate, newtup,
skipoffnum))
{
/*
* If this was a root split, the root page continues to be
* the parent and the updated tuple went to one of the
* child pages, so we just need to retry from the root
* page.
*/
if (stack->blkno != GIST_ROOT_BLKNO)
{
UnlockReleaseBuffer(stack->buffer);
xlocked = false;
state.stack = stack = stack->parent;
}
continue;
}
}
}
iid = PageGetItemId(stack->page, downlinkoffnum);
idxtuple = (IndexTuple) PageGetItem(stack->page, iid);
Assert(!GistTupleIsSkip(idxtuple));
childblkno = ItemPointerGetBlockNumber(&(idxtuple->t_tid));
/*
* Check that it's not a leftover invalid tuple from pre-9.1
*/
if (GistTupleIsInvalid(idxtuple))
ereport(ERROR,
(errmsg("index \"%s\" contains an inner tuple marked as invalid",
RelationGetRelationName(r)),
errdetail("This is caused by an incomplete page split at crash recovery before upgrading to PostgreSQL 9.1."),
errhint("Please REINDEX it.")));
/*
* Check that the key representing the target child node is
* consistent with the key we're inserting. Update it if it's not.
*/
newtup = gistgetadjusted(state.r, idxtuple, itup, giststate);
if (newtup)
{
/*
* Swap shared lock for an exclusive one. Beware, the page may
* change while we unlock/lock the page...
*/
if (!xlocked)
{
LockBuffer(stack->buffer, GIST_UNLOCK);
LockBuffer(stack->buffer, GIST_EXCLUSIVE);
xlocked = true;
stack->page = (Page) BufferGetPage(stack->buffer);
if (PageGetLSN(stack->page) != stack->lsn)
{
/* the page was changed while we unlocked it, retry */
continue;
}
}
/*
* Update the tuple.
*
* We still hold the lock after gistinserttuple(), but it
* might have to split the page to make the updated tuple fit.
* In that case the updated tuple might migrate to the other
* half of the split, so we have to go back to the parent and
* descend back to the half that's a better fit for the new
* tuple.
*/
if (gistinserttuple(&state, stack, giststate, newtup,
downlinkoffnum))
{
/*
* If this was a root split, the root page continues to be
* the parent and the updated tuple went to one of the
* child pages, so we just need to retry from the root
* page.
*/
if (stack->blkno != GIST_ROOT_BLKNO)
{
UnlockReleaseBuffer(stack->buffer);
xlocked = false;
state.stack = stack = stack->parent;
}
continue;
}
}
LockBuffer(stack->buffer, GIST_UNLOCK);
xlocked = false;
/* descend to the chosen child */
item = (GISTInsertStack *) palloc0(sizeof(GISTInsertStack));
item->blkno = childblkno;
item->parent = stack;
item->downlinkoffnum = downlinkoffnum;
item->skipoffnum = skipoffnum;
state.stack = stack = item;
}
else
{
/*
* Leaf page. Insert the new key. We've already updated all the
* parents on the way down, but we might have to split the page if
* it doesn't fit. gistinserthere() will take care of that.
*/
/*
* Swap shared lock for an exclusive one. Be careful, the page may
* change while we unlock/lock the page...
*/
if (!xlocked)
{
LockBuffer(stack->buffer, GIST_UNLOCK);
LockBuffer(stack->buffer, GIST_EXCLUSIVE);
xlocked = true;
stack->page = (Page) BufferGetPage(stack->buffer);
stack->lsn = PageGetLSN(stack->page);
if (stack->blkno == GIST_ROOT_BLKNO)
{
/*
* the only page that can become inner instead of leaf is
* the root page, so for root we should recheck it
*/
if (!GistPageIsLeaf(stack->page))
{
/*
* very rare situation: during unlock/lock index with
* number of pages = 1 was increased
*/
LockBuffer(stack->buffer, GIST_UNLOCK);
xlocked = false;
continue;
}
/*
* we don't need to check root split, because checking
* leaf/inner is enough to recognize split for root
*/
}
else if (GistFollowRight(stack->page) ||
stack->parent->lsn < GistPageGetNSN(stack->page))
{
/*
* The page was split while we momentarily unlocked the
* page. Go back to parent.
*/
UnlockReleaseBuffer(stack->buffer);
xlocked = false;
state.stack = stack = stack->parent;
continue;
}
}
/*
* The page might have been deleted after we scanned the parent
* and saw the downlink.
*/
if (GistPageIsDeleted(stack->page))
{
UnlockReleaseBuffer(stack->buffer);
xlocked = false;
state.stack = stack = stack->parent;
continue;
}
/* now state.stack->(page, buffer and blkno) points to leaf page */
gistinserttuple(&state, stack, giststate, itup,
InvalidOffsetNumber);
LockBuffer(stack->buffer, GIST_UNLOCK);
/* Release any pins we might still hold before exiting */
for (; stack; stack = stack->parent)
ReleaseBuffer(stack->buffer);
break;
}
}
}
/*
* Traverse the tree to find path from root page to specified "child" block.
*
* returns a new insertion stack, starting from the parent of "child", up
* to the root. *downlinkoffnum is set to the offset of the downlink in the
* direct parent of child.
*
* To prevent deadlocks, this should lock only one page at a time.
*/
static GISTInsertStack *