Adding upstream version 14.5.upstream/14.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 803 insertions, 0 deletions

diff --git a/src/backend/access/gist/gistget.c b/src/backend/access/gist/gistget.c
new file mode 100644
index 0000000..c8f7e78
--- /dev/null
+++ b/src/backend/access/gist/gistget.c
@@ -0,0 +1,803 @@
+/*-------------------------------------------------------------------------
+ *
+ * gistget.c
+ *	  fetch tuples from a GiST scan.
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/backend/access/gist/gistget.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/genam.h"
+#include "access/gist_private.h"
+#include "access/relscan.h"
+#include "lib/pairingheap.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "storage/lmgr.h"
+#include "storage/predicate.h"
+#include "utils/float.h"
+#include "utils/memutils.h"
+#include "utils/rel.h"
+
+/*
+ * gistkillitems() -- set LP_DEAD state for items an indexscan caller has
+ * told us were killed.
+ *
+ * We re-read page here, so it's important to check page LSN. If the page
+ * has been modified since the last read (as determined by LSN), we cannot
+ * flag any entries because it is possible that the old entry was vacuumed
+ * away and the TID was re-used by a completely different heap tuple.
+ */
+static void
+gistkillitems(IndexScanDesc scan)
+{
+	GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
+	Buffer		buffer;
+	Page		page;
+	OffsetNumber offnum;
+	ItemId		iid;
+	int			i;
+	bool		killedsomething = false;
+
+	Assert(so->curBlkno != InvalidBlockNumber);
+	Assert(!XLogRecPtrIsInvalid(so->curPageLSN));
+	Assert(so->killedItems != NULL);
+
+	buffer = ReadBuffer(scan->indexRelation, so->curBlkno);
+	if (!BufferIsValid(buffer))
+		return;
+
+	LockBuffer(buffer, GIST_SHARE);
+	gistcheckpage(scan->indexRelation, buffer);
+	page = BufferGetPage(buffer);
+
+	/*
+	 * If page LSN differs it means that the page was modified since the last
+	 * read. killedItems could be not valid so LP_DEAD hints applying is not
+	 * safe.
+	 */
+	if (BufferGetLSNAtomic(buffer) != so->curPageLSN)
+	{
+		UnlockReleaseBuffer(buffer);
+		so->numKilled = 0;		/* reset counter */
+		return;
+	}
+
+	Assert(GistPageIsLeaf(page));
+
+	/*
+	 * Mark all killedItems as dead. We need no additional recheck, because,
+	 * if page was modified, curPageLSN must have changed.
+	 */
+	for (i = 0; i < so->numKilled; i++)
+	{
+		offnum = so->killedItems[i];
+		iid = PageGetItemId(page, offnum);
+		ItemIdMarkDead(iid);
+		killedsomething = true;
+	}
+
+	if (killedsomething)
+	{
+		GistMarkPageHasGarbage(page);
+		MarkBufferDirtyHint(buffer, true);
+	}
+
+	UnlockReleaseBuffer(buffer);
+
+	/*
+	 * Always reset the scan state, so we don't look for same items on other
+	 * pages.
+	 */
+	so->numKilled = 0;
+}
+
+/*
+ * gistindex_keytest() -- does this index tuple satisfy the scan key(s)?
+ *
+ * The index tuple might represent either a heap tuple or a lower index page,
+ * depending on whether the containing page is a leaf page or not.
+ *
+ * On success return for a heap tuple, *recheck_p is set to indicate whether
+ * the quals need to be rechecked.  We recheck if any of the consistent()
+ * functions request it.  recheck is not interesting when examining a non-leaf
+ * entry, since we must visit the lower index page if there's any doubt.
+ * Similarly, *recheck_distances_p is set to indicate whether the distances
+ * need to be rechecked, and it is also ignored for non-leaf entries.
+ *
+ * If we are doing an ordered scan, so->distances[] is filled with distance
+ * data from the distance() functions before returning success.
+ *
+ * We must decompress the key in the IndexTuple before passing it to the
+ * sk_funcs (which actually are the opclass Consistent or Distance methods).
+ *
+ * Note that this function is always invoked in a short-lived memory context,
+ * so we don't need to worry about cleaning up allocated memory, either here
+ * or in the implementation of any Consistent or Distance methods.
+ */
+static bool
+gistindex_keytest(IndexScanDesc scan,
+				  IndexTuple tuple,
+				  Page page,
+				  OffsetNumber offset,
+				  bool *recheck_p,
+				  bool *recheck_distances_p)
+{
+	GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
+	GISTSTATE  *giststate = so->giststate;
+	ScanKey		key = scan->keyData;
+	int			keySize = scan->numberOfKeys;
+	IndexOrderByDistance *distance_p;
+	Relation	r = scan->indexRelation;
+
+	*recheck_p = false;
+	*recheck_distances_p = false;
+
+	/*
+	 * If it's a leftover invalid tuple from pre-9.1, treat it as a match with
+	 * minimum possible distances.  This means we'll always follow it to the
+	 * referenced page.
+	 */
+	if (GistTupleIsInvalid(tuple))
+	{
+		int			i;
+
+		if (GistPageIsLeaf(page))	/* shouldn't happen */
+			elog(ERROR, "invalid GiST tuple found on leaf page");
+		for (i = 0; i < scan->numberOfOrderBys; i++)
+		{
+			so->distances[i].value = -get_float8_infinity();
+			so->distances[i].isnull = false;
+		}
+		return true;
+	}
+
+	/* Check whether it matches according to the Consistent functions */
+	while (keySize > 0)
+	{
+		Datum		datum;
+		bool		isNull;
+
+		datum = index_getattr(tuple,
+							  key->sk_attno,
+							  giststate->leafTupdesc,
+							  &isNull);
+
+		if (key->sk_flags & SK_ISNULL)
+		{
+			/*
+			 * On non-leaf page we can't conclude that child hasn't NULL
+			 * values because of assumption in GiST: union (VAL, NULL) is VAL.
+			 * But if on non-leaf page key IS NULL, then all children are
+			 * NULL.
+			 */
+			if (key->sk_flags & SK_SEARCHNULL)
+			{
+				if (GistPageIsLeaf(page) && !isNull)
+					return false;
+			}
+			else
+			{
+				Assert(key->sk_flags & SK_SEARCHNOTNULL);
+				if (isNull)
+					return false;
+			}
+		}
+		else if (isNull)
+		{
+			return false;
+		}
+		else
+		{
+			Datum		test;
+			bool		recheck;
+			GISTENTRY	de;
+
+			gistdentryinit(giststate, key->sk_attno - 1, &de,
+						   datum, r, page, offset,
+						   false, isNull);
+
+			/*
+			 * Call the Consistent function to evaluate the test.  The
+			 * arguments are the index datum (as a GISTENTRY*), the comparison
+			 * datum, the comparison operator's strategy number and subtype
+			 * from pg_amop, and the recheck flag.
+			 *
+			 * (Presently there's no need to pass the subtype since it'll
+			 * always be zero, but might as well pass it for possible future
+			 * use.)
+			 *
+			 * We initialize the recheck flag to true (the safest assumption)
+			 * in case the Consistent function forgets to set it.
+			 */
+			recheck = true;
+
+			test = FunctionCall5Coll(&key->sk_func,
+									 key->sk_collation,
+									 PointerGetDatum(&de),
+									 key->sk_argument,
+									 Int16GetDatum(key->sk_strategy),
+									 ObjectIdGetDatum(key->sk_subtype),
+									 PointerGetDatum(&recheck));
+
+			if (!DatumGetBool(test))
+				return false;
+			*recheck_p |= recheck;
+		}
+
+		key++;
+		keySize--;
+	}
+
+	/* OK, it passes --- now let's compute the distances */
+	key = scan->orderByData;
+	distance_p = so->distances;
+	keySize = scan->numberOfOrderBys;
+	while (keySize > 0)
+	{
+		Datum		datum;
+		bool		isNull;
+
+		datum = index_getattr(tuple,
+							  key->sk_attno,
+							  giststate->leafTupdesc,
+							  &isNull);
+
+		if ((key->sk_flags & SK_ISNULL) || isNull)
+		{
+			/* Assume distance computes as null */
+			distance_p->value = 0.0;
+			distance_p->isnull = true;
+		}
+		else
+		{
+			Datum		dist;
+			bool		recheck;
+			GISTENTRY	de;
+
+			gistdentryinit(giststate, key->sk_attno - 1, &de,
+						   datum, r, page, offset,
+						   false, isNull);
+
+			/*
+			 * Call the Distance function to evaluate the distance.  The
+			 * arguments are the index datum (as a GISTENTRY*), the comparison
+			 * datum, the ordering operator's strategy number and subtype from
+			 * pg_amop, and the recheck flag.
+			 *
+			 * (Presently there's no need to pass the subtype since it'll
+			 * always be zero, but might as well pass it for possible future
+			 * use.)
+			 *
+			 * If the function sets the recheck flag, the returned distance is
+			 * a lower bound on the true distance and needs to be rechecked.
+			 * We initialize the flag to 'false'.  This flag was added in
+			 * version 9.5; distance functions written before that won't know
+			 * about the flag, but are expected to never be lossy.
+			 */
+			recheck = false;
+			dist = FunctionCall5Coll(&key->sk_func,
+									 key->sk_collation,
+									 PointerGetDatum(&de),
+									 key->sk_argument,
+									 Int16GetDatum(key->sk_strategy),
+									 ObjectIdGetDatum(key->sk_subtype),
+									 PointerGetDatum(&recheck));
+			*recheck_distances_p |= recheck;
+			distance_p->value = DatumGetFloat8(dist);
+			distance_p->isnull = false;
+		}
+
+		key++;
+		distance_p++;
+		keySize--;
+	}
+
+	return true;
+}
+
+/*
+ * Scan all items on the GiST index page identified by *pageItem, and insert
+ * them into the queue (or directly to output areas)
+ *
+ * scan: index scan we are executing
+ * pageItem: search queue item identifying an index page to scan
+ * myDistances: distances array associated with pageItem, or NULL at the root
+ * tbm: if not NULL, gistgetbitmap's output bitmap
+ * ntids: if not NULL, gistgetbitmap's output tuple counter
+ *
+ * If tbm/ntids aren't NULL, we are doing an amgetbitmap scan, and heap
+ * tuples should be reported directly into the bitmap.  If they are NULL,
+ * we're doing a plain or ordered indexscan.  For a plain indexscan, heap
+ * tuple TIDs are returned into so->pageData[].  For an ordered indexscan,
+ * heap tuple TIDs are pushed into individual search queue items.  In an
+ * index-only scan, reconstructed index tuples are returned along with the
+ * TIDs.
+ *
+ * If we detect that the index page has split since we saw its downlink
+ * in the parent, we push its new right sibling onto the queue so the
+ * sibling will be processed next.
+ */
+static void
+gistScanPage(IndexScanDesc scan, GISTSearchItem *pageItem,
+			 IndexOrderByDistance *myDistances, TIDBitmap *tbm, int64 *ntids)
+{
+	GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
+	GISTSTATE  *giststate = so->giststate;
+	Relation	r = scan->indexRelation;
+	Buffer		buffer;
+	Page		page;
+	GISTPageOpaque opaque;
+	OffsetNumber maxoff;
+	OffsetNumber i;
+	MemoryContext oldcxt;
+
+	Assert(!GISTSearchItemIsHeap(*pageItem));
+
+	buffer = ReadBuffer(scan->indexRelation, pageItem->blkno);
+	LockBuffer(buffer, GIST_SHARE);
+	PredicateLockPage(r, BufferGetBlockNumber(buffer), scan->xs_snapshot);
+	gistcheckpage(scan->indexRelation, buffer);
+	page = BufferGetPage(buffer);
+	TestForOldSnapshot(scan->xs_snapshot, r, page);
+	opaque = GistPageGetOpaque(page);
+
+	/*
+	 * Check if we need to follow the rightlink. We need to follow it if the
+	 * page was concurrently split since we visited the parent (in which case
+	 * parentlsn < nsn), or if the system crashed after a page split but
+	 * before the downlink was inserted into the parent.
+	 */
+	if (!XLogRecPtrIsInvalid(pageItem->data.parentlsn) &&
+		(GistFollowRight(page) ||
+		 pageItem->data.parentlsn < GistPageGetNSN(page)) &&
+		opaque->rightlink != InvalidBlockNumber /* sanity check */ )
+	{
+		/* There was a page split, follow right link to add pages */
+		GISTSearchItem *item;
+
+		/* This can't happen when starting at the root */
+		Assert(myDistances != NULL);
+
+		oldcxt = MemoryContextSwitchTo(so->queueCxt);
+
+		/* Create new GISTSearchItem for the right sibling index page */
+		item = palloc(SizeOfGISTSearchItem(scan->numberOfOrderBys));
+		item->blkno = opaque->rightlink;
+		item->data.parentlsn = pageItem->data.parentlsn;
+
+		/* Insert it into the queue using same distances as for this page */
+		memcpy(item->distances, myDistances,
+			   sizeof(item->distances[0]) * scan->numberOfOrderBys);
+
+		pairingheap_add(so->queue, &item->phNode);
+
+		MemoryContextSwitchTo(oldcxt);
+	}
+
+	/*
+	 * Check if the page was deleted after we saw the downlink. There's
+	 * nothing of interest on a deleted page. Note that we must do this after
+	 * checking the NSN for concurrent splits! It's possible that the page
+	 * originally contained some tuples that are visible to us, but was split
+	 * so that all the visible tuples were moved to another page, and then
+	 * this page was deleted.
+	 */
+	if (GistPageIsDeleted(page))
+	{
+		UnlockReleaseBuffer(buffer);
+		return;
+	}
+
+	so->nPageData = so->curPageData = 0;
+	scan->xs_hitup = NULL;		/* might point into pageDataCxt */
+	if (so->pageDataCxt)
+		MemoryContextReset(so->pageDataCxt);
+
+	/*
+	 * We save the LSN of the page as we read it, so that we know whether it
+	 * safe to apply LP_DEAD hints to the page later. This allows us to drop
+	 * the pin for MVCC scans, which allows vacuum to avoid blocking.
+	 */
+	so->curPageLSN = BufferGetLSNAtomic(buffer);
+
+	/*
+	 * check all tuples on page
+	 */
+	maxoff = PageGetMaxOffsetNumber(page);
+	for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
+	{
+		ItemId		iid = PageGetItemId(page, i);
+		IndexTuple	it;
+		bool		match;
+		bool		recheck;
+		bool		recheck_distances;
+
+		/*
+		 * If the scan specifies not to return killed tuples, then we treat a
+		 * killed tuple as not passing the qual.
+		 */
+		if (scan->ignore_killed_tuples && ItemIdIsDead(iid))
+			continue;
+
+		it = (IndexTuple) PageGetItem(page, iid);
+
+		/*
+		 * Must call gistindex_keytest in tempCxt, and clean up any leftover
+		 * junk afterward.
+		 */
+		oldcxt = MemoryContextSwitchTo(so->giststate->tempCxt);
+
+		match = gistindex_keytest(scan, it, page, i,
+								  &recheck, &recheck_distances);
+
+		MemoryContextSwitchTo(oldcxt);
+		MemoryContextReset(so->giststate->tempCxt);
+
+		/* Ignore tuple if it doesn't match */
+		if (!match)
+			continue;
+
+		if (tbm && GistPageIsLeaf(page))
+		{
+			/*
+			 * getbitmap scan, so just push heap tuple TIDs into the bitmap
+			 * without worrying about ordering
+			 */
+			tbm_add_tuples(tbm, &it->t_tid, 1, recheck);
+			(*ntids)++;
+		}
+		else if (scan->numberOfOrderBys == 0 && GistPageIsLeaf(page))
+		{
+			/*
+			 * Non-ordered scan, so report tuples in so->pageData[]
+			 */
+			so->pageData[so->nPageData].heapPtr = it->t_tid;
+			so->pageData[so->nPageData].recheck = recheck;
+			so->pageData[so->nPageData].offnum = i;
+
+			/*
+			 * In an index-only scan, also fetch the data from the tuple.  The
+			 * reconstructed tuples are stored in pageDataCxt.
+			 */
+			if (scan->xs_want_itup)
+			{
+				oldcxt = MemoryContextSwitchTo(so->pageDataCxt);
+				so->pageData[so->nPageData].recontup =
+					gistFetchTuple(giststate, r, it);
+				MemoryContextSwitchTo(oldcxt);
+			}
+			so->nPageData++;
+		}
+		else
+		{
+			/*
+			 * Must push item into search queue.  We get here for any lower
+			 * index page, and also for heap tuples if doing an ordered
+			 * search.
+			 */
+			GISTSearchItem *item;
+			int			nOrderBys = scan->numberOfOrderBys;
+
+			oldcxt = MemoryContextSwitchTo(so->queueCxt);
+
+			/* Create new GISTSearchItem for this item */
+			item = palloc(SizeOfGISTSearchItem(scan->numberOfOrderBys));
+
+			if (GistPageIsLeaf(page))
+			{
+				/* Creating heap-tuple GISTSearchItem */
+				item->blkno = InvalidBlockNumber;
+				item->data.heap.heapPtr = it->t_tid;
+				item->data.heap.recheck = recheck;
+				item->data.heap.recheckDistances = recheck_distances;
+
+				/*
+				 * In an index-only scan, also fetch the data from the tuple.
+				 */
+				if (scan->xs_want_itup)
+					item->data.heap.recontup = gistFetchTuple(giststate, r, it);
+			}
+			else
+			{
+				/* Creating index-page GISTSearchItem */
+				item->blkno = ItemPointerGetBlockNumber(&it->t_tid);
+
+				/*
+				 * LSN of current page is lsn of parent page for child. We
+				 * only have a shared lock, so we need to get the LSN
+				 * atomically.
+				 */
+				item->data.parentlsn = BufferGetLSNAtomic(buffer);
+			}
+
+			/* Insert it into the queue using new distance data */
+			memcpy(item->distances, so->distances,
+				   sizeof(item->distances[0]) * nOrderBys);
+
+			pairingheap_add(so->queue, &item->phNode);
+
+			MemoryContextSwitchTo(oldcxt);
+		}
+	}
+
+	UnlockReleaseBuffer(buffer);
+}
+
+/*
+ * Extract next item (in order) from search queue
+ *
+ * Returns a GISTSearchItem or NULL.  Caller must pfree item when done with it.
+ */
+static GISTSearchItem *
+getNextGISTSearchItem(GISTScanOpaque so)
+{
+	GISTSearchItem *item;
+
+	if (!pairingheap_is_empty(so->queue))
+	{
+		item = (GISTSearchItem *) pairingheap_remove_first(so->queue);
+	}
+	else
+	{
+		/* Done when both heaps are empty */
+		item = NULL;
+	}
+
+	/* Return item; caller is responsible to pfree it */
+	return item;
+}
+
+/*
+ * Fetch next heap tuple in an ordered search
+ */
+static bool
+getNextNearest(IndexScanDesc scan)
+{
+	GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
+	bool		res = false;
+
+	if (scan->xs_hitup)
+	{
+		/* free previously returned tuple */
+		pfree(scan->xs_hitup);
+		scan->xs_hitup = NULL;
+	}
+
+	do
+	{
+		GISTSearchItem *item = getNextGISTSearchItem(so);
+
+		if (!item)
+			break;
+
+		if (GISTSearchItemIsHeap(*item))
+		{
+			/* found a heap item at currently minimal distance */
+			scan->xs_heaptid = item->data.heap.heapPtr;
+			scan->xs_recheck = item->data.heap.recheck;
+
+			index_store_float8_orderby_distances(scan, so->orderByTypes,
+												 item->distances,
+												 item->data.heap.recheckDistances);
+
+			/* in an index-only scan, also return the reconstructed tuple. */
+			if (scan->xs_want_itup)
+				scan->xs_hitup = item->data.heap.recontup;
+			res = true;
+		}
+		else
+		{
+			/* visit an index page, extract its items into queue */
+			CHECK_FOR_INTERRUPTS();
+
+			gistScanPage(scan, item, item->distances, NULL, NULL);
+		}
+
+		pfree(item);
+	} while (!res);
+
+	return res;
+}
+
+/*
+ * gistgettuple() -- Get the next tuple in the scan
+ */
+bool
+gistgettuple(IndexScanDesc scan, ScanDirection dir)
+{
+	GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
+
+	if (dir != ForwardScanDirection)
+		elog(ERROR, "GiST only supports forward scan direction");
+
+	if (!so->qual_ok)
+		return false;
+
+	if (so->firstCall)
+	{
+		/* Begin the scan by processing the root page */
+		GISTSearchItem fakeItem;
+
+		pgstat_count_index_scan(scan->indexRelation);
+
+		so->firstCall = false;
+		so->curPageData = so->nPageData = 0;
+		scan->xs_hitup = NULL;
+		if (so->pageDataCxt)
+			MemoryContextReset(so->pageDataCxt);
+
+		fakeItem.blkno = GIST_ROOT_BLKNO;
+		memset(&fakeItem.data.parentlsn, 0, sizeof(GistNSN));
+		gistScanPage(scan, &fakeItem, NULL, NULL, NULL);
+	}
+
+	if (scan->numberOfOrderBys > 0)
+	{
+		/* Must fetch tuples in strict distance order */
+		return getNextNearest(scan);
+	}
+	else
+	{
+		/* Fetch tuples index-page-at-a-time */
+		for (;;)
+		{
+			if (so->curPageData < so->nPageData)
+			{
+				if (scan->kill_prior_tuple && so->curPageData > 0)
+				{
+
+					if (so->killedItems == NULL)
+					{
+						MemoryContext oldCxt =
+						MemoryContextSwitchTo(so->giststate->scanCxt);
+
+						so->killedItems =
+							(OffsetNumber *) palloc(MaxIndexTuplesPerPage
+													* sizeof(OffsetNumber));
+
+						MemoryContextSwitchTo(oldCxt);
+					}
+					if (so->numKilled < MaxIndexTuplesPerPage)
+						so->killedItems[so->numKilled++] =
+							so->pageData[so->curPageData - 1].offnum;
+				}
+				/* continuing to return tuples from a leaf page */
+				scan->xs_heaptid = so->pageData[so->curPageData].heapPtr;
+				scan->xs_recheck = so->pageData[so->curPageData].recheck;
+
+				/* in an index-only scan, also return the reconstructed tuple */
+				if (scan->xs_want_itup)
+					scan->xs_hitup = so->pageData[so->curPageData].recontup;
+
+				so->curPageData++;
+
+				return true;
+			}
+
+			/*
+			 * Check the last returned tuple and add it to killedItems if
+			 * necessary
+			 */
+			if (scan->kill_prior_tuple
+				&& so->curPageData > 0
+				&& so->curPageData == so->nPageData)
+			{
+
+				if (so->killedItems == NULL)
+				{
+					MemoryContext oldCxt =
+					MemoryContextSwitchTo(so->giststate->scanCxt);
+
+					so->killedItems =
+						(OffsetNumber *) palloc(MaxIndexTuplesPerPage
+												* sizeof(OffsetNumber));
+
+					MemoryContextSwitchTo(oldCxt);
+				}
+				if (so->numKilled < MaxIndexTuplesPerPage)
+					so->killedItems[so->numKilled++] =
+						so->pageData[so->curPageData - 1].offnum;
+			}
+			/* find and process the next index page */
+			do
+			{
+				GISTSearchItem *item;
+
+				if ((so->curBlkno != InvalidBlockNumber) && (so->numKilled > 0))
+					gistkillitems(scan);
+
+				item = getNextGISTSearchItem(so);
+
+				if (!item)
+					return false;
+
+				CHECK_FOR_INTERRUPTS();
+
+				/* save current item BlockNumber for next gistkillitems() call */
+				so->curBlkno = item->blkno;
+
+				/*
+				 * While scanning a leaf page, ItemPointers of matching heap
+				 * tuples are stored in so->pageData.  If there are any on
+				 * this page, we fall out of the inner "do" and loop around to
+				 * return them.
+				 */
+				gistScanPage(scan, item, item->distances, NULL, NULL);
+
+				pfree(item);
+			} while (so->nPageData == 0);
+		}
+	}
+}
+
+/*
+ * gistgetbitmap() -- Get a bitmap of all heap tuple locations
+ */
+int64
+gistgetbitmap(IndexScanDesc scan, TIDBitmap *tbm)
+{
+	GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
+	int64		ntids = 0;
+	GISTSearchItem fakeItem;
+
+	if (!so->qual_ok)
+		return 0;
+
+	pgstat_count_index_scan(scan->indexRelation);
+
+	/* Begin the scan by processing the root page */
+	so->curPageData = so->nPageData = 0;
+	scan->xs_hitup = NULL;
+	if (so->pageDataCxt)
+		MemoryContextReset(so->pageDataCxt);
+
+	fakeItem.blkno = GIST_ROOT_BLKNO;
+	memset(&fakeItem.data.parentlsn, 0, sizeof(GistNSN));
+	gistScanPage(scan, &fakeItem, NULL, tbm, &ntids);
+
+	/*
+	 * While scanning a leaf page, ItemPointers of matching heap tuples will
+	 * be stored directly into tbm, so we don't need to deal with them here.
+	 */
+	for (;;)
+	{
+		GISTSearchItem *item = getNextGISTSearchItem(so);
+
+		if (!item)
+			break;
+
+		CHECK_FOR_INTERRUPTS();
+
+		gistScanPage(scan, item, item->distances, tbm, &ntids);
+
+		pfree(item);
+	}
+
+	return ntids;
+}
+
+/*
+ * Can we do index-only scans on the given index column?
+ *
+ * Opclasses that implement a fetch function support index-only scans.
+ * Opclasses without compression functions also support index-only scans.
+ * Included attributes always can be fetched for index-only scans.
+ */
+bool
+gistcanreturn(Relation index, int attno)
+{
+	if (attno > IndexRelationGetNumberOfKeyAttributes(index) ||
+		OidIsValid(index_getprocid(index, attno, GIST_FETCH_PROC)) ||
+		!OidIsValid(index_getprocid(index, attno, GIST_COMPRESS_PROC)))
+		return true;
+	else
+		return false;
+}