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diff --git a/src/backend/access/heap/hio.c b/src/backend/access/heap/hio.c
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+/*-------------------------------------------------------------------------
+ *
+ * hio.c
+ * POSTGRES heap access method input/output code.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ * src/backend/access/heap/hio.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "access/heapam.h"
+#include "access/hio.h"
+#include "access/htup_details.h"
+#include "access/visibilitymap.h"
+#include "storage/bufmgr.h"
+#include "storage/freespace.h"
+#include "storage/lmgr.h"
+#include "storage/smgr.h"
+
+
+/*
+ * RelationPutHeapTuple - place tuple at specified page
+ *
+ * !!! EREPORT(ERROR) IS DISALLOWED HERE !!! Must PANIC on failure!!!
+ *
+ * Note - caller must hold BUFFER_LOCK_EXCLUSIVE on the buffer.
+ */
+void
+RelationPutHeapTuple(Relation relation,
+ Buffer buffer,
+ HeapTuple tuple,
+ bool token)
+{
+ Page pageHeader;
+ OffsetNumber offnum;
+
+ /*
+ * A tuple that's being inserted speculatively should already have its
+ * token set.
+ */
+ Assert(!token || HeapTupleHeaderIsSpeculative(tuple->t_data));
+
+ /*
+ * Do not allow tuples with invalid combinations of hint bits to be placed
+ * on a page. This combination is detected as corruption by the
+ * contrib/amcheck logic, so if you disable this assertion, make
+ * corresponding changes there.
+ */
+ Assert(!((tuple->t_data->t_infomask & HEAP_XMAX_COMMITTED) &&
+ (tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI)));
+
+ /* Add the tuple to the page */
+ pageHeader = BufferGetPage(buffer);
+
+ offnum = PageAddItem(pageHeader, (Item) tuple->t_data,
+ tuple->t_len, InvalidOffsetNumber, false, true);
+
+ if (offnum == InvalidOffsetNumber)
+ elog(PANIC, "failed to add tuple to page");
+
+ /* Update tuple->t_self to the actual position where it was stored */
+ ItemPointerSet(&(tuple->t_self), BufferGetBlockNumber(buffer), offnum);
+
+ /*
+ * Insert the correct position into CTID of the stored tuple, too (unless
+ * this is a speculative insertion, in which case the token is held in
+ * CTID field instead)
+ */
+ if (!token)
+ {
+ ItemId itemId = PageGetItemId(pageHeader, offnum);
+ HeapTupleHeader item = (HeapTupleHeader) PageGetItem(pageHeader, itemId);
+
+ item->t_ctid = tuple->t_self;
+ }
+}
+
+/*
+ * Read in a buffer in mode, using bulk-insert strategy if bistate isn't NULL.
+ */
+static Buffer
+ReadBufferBI(Relation relation, BlockNumber targetBlock,
+ ReadBufferMode mode, BulkInsertState bistate)
+{
+ Buffer buffer;
+
+ /* If not bulk-insert, exactly like ReadBuffer */
+ if (!bistate)
+ return ReadBufferExtended(relation, MAIN_FORKNUM, targetBlock,
+ mode, NULL);
+
+ /* If we have the desired block already pinned, re-pin and return it */
+ if (bistate->current_buf != InvalidBuffer)
+ {
+ if (BufferGetBlockNumber(bistate->current_buf) == targetBlock)
+ {
+ /*
+ * Currently the LOCK variants are only used for extending
+ * relation, which should never reach this branch.
+ */
+ Assert(mode != RBM_ZERO_AND_LOCK &&
+ mode != RBM_ZERO_AND_CLEANUP_LOCK);
+
+ IncrBufferRefCount(bistate->current_buf);
+ return bistate->current_buf;
+ }
+ /* ... else drop the old buffer */
+ ReleaseBuffer(bistate->current_buf);
+ bistate->current_buf = InvalidBuffer;
+ }
+
+ /* Perform a read using the buffer strategy */
+ buffer = ReadBufferExtended(relation, MAIN_FORKNUM, targetBlock,
+ mode, bistate->strategy);
+
+ /* Save the selected block as target for future inserts */
+ IncrBufferRefCount(buffer);
+ bistate->current_buf = buffer;
+
+ return buffer;
+}
+
+/*
+ * For each heap page which is all-visible, acquire a pin on the appropriate
+ * visibility map page, if we haven't already got one.
+ *
+ * buffer2 may be InvalidBuffer, if only one buffer is involved. buffer1
+ * must not be InvalidBuffer. If both buffers are specified, block1 must
+ * be less than block2.
+ */
+static void
+GetVisibilityMapPins(Relation relation, Buffer buffer1, Buffer buffer2,
+ BlockNumber block1, BlockNumber block2,
+ Buffer *vmbuffer1, Buffer *vmbuffer2)
+{
+ bool need_to_pin_buffer1;
+ bool need_to_pin_buffer2;
+
+ Assert(BufferIsValid(buffer1));
+ Assert(buffer2 == InvalidBuffer || block1 <= block2);
+
+ while (1)
+ {
+ /* Figure out which pins we need but don't have. */
+ need_to_pin_buffer1 = PageIsAllVisible(BufferGetPage(buffer1))
+ && !visibilitymap_pin_ok(block1, *vmbuffer1);
+ need_to_pin_buffer2 = buffer2 != InvalidBuffer
+ && PageIsAllVisible(BufferGetPage(buffer2))
+ && !visibilitymap_pin_ok(block2, *vmbuffer2);
+ if (!need_to_pin_buffer1 && !need_to_pin_buffer2)
+ return;
+
+ /* We must unlock both buffers before doing any I/O. */
+ LockBuffer(buffer1, BUFFER_LOCK_UNLOCK);
+ if (buffer2 != InvalidBuffer && buffer2 != buffer1)
+ LockBuffer(buffer2, BUFFER_LOCK_UNLOCK);
+
+ /* Get pins. */
+ if (need_to_pin_buffer1)
+ visibilitymap_pin(relation, block1, vmbuffer1);
+ if (need_to_pin_buffer2)
+ visibilitymap_pin(relation, block2, vmbuffer2);
+
+ /* Relock buffers. */
+ LockBuffer(buffer1, BUFFER_LOCK_EXCLUSIVE);
+ if (buffer2 != InvalidBuffer && buffer2 != buffer1)
+ LockBuffer(buffer2, BUFFER_LOCK_EXCLUSIVE);
+
+ /*
+ * If there are two buffers involved and we pinned just one of them,
+ * it's possible that the second one became all-visible while we were
+ * busy pinning the first one. If it looks like that's a possible
+ * scenario, we'll need to make a second pass through this loop.
+ */
+ if (buffer2 == InvalidBuffer || buffer1 == buffer2
+ || (need_to_pin_buffer1 && need_to_pin_buffer2))
+ break;
+ }
+}
+
+/*
+ * Extend a relation by multiple blocks to avoid future contention on the
+ * relation extension lock. Our goal is to pre-extend the relation by an
+ * amount which ramps up as the degree of contention ramps up, but limiting
+ * the result to some sane overall value.
+ */
+static void
+RelationAddExtraBlocks(Relation relation, BulkInsertState bistate)
+{
+ BlockNumber blockNum,
+ firstBlock = InvalidBlockNumber;
+ int extraBlocks;
+ int lockWaiters;
+
+ /* Use the length of the lock wait queue to judge how much to extend. */
+ lockWaiters = RelationExtensionLockWaiterCount(relation);
+ if (lockWaiters <= 0)
+ return;
+
+ /*
+ * It might seem like multiplying the number of lock waiters by as much as
+ * 20 is too aggressive, but benchmarking revealed that smaller numbers
+ * were insufficient. 512 is just an arbitrary cap to prevent
+ * pathological results.
+ */
+ extraBlocks = Min(512, lockWaiters * 20);
+
+ do
+ {
+ Buffer buffer;
+ Page page;
+ Size freespace;
+
+ /*
+ * Extend by one page. This should generally match the main-line
+ * extension code in RelationGetBufferForTuple, except that we hold
+ * the relation extension lock throughout, and we don't immediately
+ * initialize the page (see below).
+ */
+ buffer = ReadBufferBI(relation, P_NEW, RBM_ZERO_AND_LOCK, bistate);
+ page = BufferGetPage(buffer);
+
+ if (!PageIsNew(page))
+ elog(ERROR, "page %u of relation \"%s\" should be empty but is not",
+ BufferGetBlockNumber(buffer),
+ RelationGetRelationName(relation));
+
+ /*
+ * Add the page to the FSM without initializing. If we were to
+ * initialize here, the page would potentially get flushed out to disk
+ * before we add any useful content. There's no guarantee that that'd
+ * happen before a potential crash, so we need to deal with
+ * uninitialized pages anyway, thus avoid the potential for
+ * unnecessary writes.
+ */
+
+ /* we'll need this info below */
+ blockNum = BufferGetBlockNumber(buffer);
+ freespace = BufferGetPageSize(buffer) - SizeOfPageHeaderData;
+
+ UnlockReleaseBuffer(buffer);
+
+ /* Remember first block number thus added. */
+ if (firstBlock == InvalidBlockNumber)
+ firstBlock = blockNum;
+
+ /*
+ * Immediately update the bottom level of the FSM. This has a good
+ * chance of making this page visible to other concurrently inserting
+ * backends, and we want that to happen without delay.
+ */
+ RecordPageWithFreeSpace(relation, blockNum, freespace);
+ }
+ while (--extraBlocks > 0);
+
+ /*
+ * Updating the upper levels of the free space map is too expensive to do
+ * for every block, but it's worth doing once at the end to make sure that
+ * subsequent insertion activity sees all of those nifty free pages we
+ * just inserted.
+ */
+ FreeSpaceMapVacuumRange(relation, firstBlock, blockNum + 1);
+}
+
+/*
+ * RelationGetBufferForTuple
+ *
+ * Returns pinned and exclusive-locked buffer of a page in given relation
+ * with free space >= given len.
+ *
+ * If otherBuffer is not InvalidBuffer, then it references a previously
+ * pinned buffer of another page in the same relation; on return, this
+ * buffer will also be exclusive-locked. (This case is used by heap_update;
+ * the otherBuffer contains the tuple being updated.)
+ *
+ * The reason for passing otherBuffer is that if two backends are doing
+ * concurrent heap_update operations, a deadlock could occur if they try
+ * to lock the same two buffers in opposite orders. To ensure that this
+ * can't happen, we impose the rule that buffers of a relation must be
+ * locked in increasing page number order. This is most conveniently done
+ * by having RelationGetBufferForTuple lock them both, with suitable care
+ * for ordering.
+ *
+ * NOTE: it is unlikely, but not quite impossible, for otherBuffer to be the
+ * same buffer we select for insertion of the new tuple (this could only
+ * happen if space is freed in that page after heap_update finds there's not
+ * enough there). In that case, the page will be pinned and locked only once.
+ *
+ * We also handle the possibility that the all-visible flag will need to be
+ * cleared on one or both pages. If so, pin on the associated visibility map
+ * page must be acquired before acquiring buffer lock(s), to avoid possibly
+ * doing I/O while holding buffer locks. The pins are passed back to the
+ * caller using the input-output arguments vmbuffer and vmbuffer_other.
+ * Note that in some cases the caller might have already acquired such pins,
+ * which is indicated by these arguments not being InvalidBuffer on entry.
+ *
+ * We normally use FSM to help us find free space. However,
+ * if HEAP_INSERT_SKIP_FSM is specified, we just append a new empty page to
+ * the end of the relation if the tuple won't fit on the current target page.
+ * This can save some cycles when we know the relation is new and doesn't
+ * contain useful amounts of free space.
+ *
+ * HEAP_INSERT_SKIP_FSM is also useful for non-WAL-logged additions to a
+ * relation, if the caller holds exclusive lock and is careful to invalidate
+ * relation's smgr_targblock before the first insertion --- that ensures that
+ * all insertions will occur into newly added pages and not be intermixed
+ * with tuples from other transactions. That way, a crash can't risk losing
+ * any committed data of other transactions. (See heap_insert's comments
+ * for additional constraints needed for safe usage of this behavior.)
+ *
+ * The caller can also provide a BulkInsertState object to optimize many
+ * insertions into the same relation. This keeps a pin on the current
+ * insertion target page (to save pin/unpin cycles) and also passes a
+ * BULKWRITE buffer selection strategy object to the buffer manager.
+ * Passing NULL for bistate selects the default behavior.
+ *
+ * We don't fill existing pages further than the fillfactor, except for large
+ * tuples in nearly-empty pages. This is OK since this routine is not
+ * consulted when updating a tuple and keeping it on the same page, which is
+ * the scenario fillfactor is meant to reserve space for.
+ *
+ * ereport(ERROR) is allowed here, so this routine *must* be called
+ * before any (unlogged) changes are made in buffer pool.
+ */
+Buffer
+RelationGetBufferForTuple(Relation relation, Size len,
+ Buffer otherBuffer, int options,
+ BulkInsertState bistate,
+ Buffer *vmbuffer, Buffer *vmbuffer_other)
+{
+ bool use_fsm = !(options & HEAP_INSERT_SKIP_FSM);
+ Buffer buffer = InvalidBuffer;
+ Page page;
+ Size nearlyEmptyFreeSpace,
+ pageFreeSpace = 0,
+ saveFreeSpace = 0,
+ targetFreeSpace = 0;
+ BlockNumber targetBlock,
+ otherBlock;
+ bool needLock;
+
+ len = MAXALIGN(len); /* be conservative */
+
+ /* Bulk insert is not supported for updates, only inserts. */
+ Assert(otherBuffer == InvalidBuffer || !bistate);
+
+ /*
+ * If we're gonna fail for oversize tuple, do it right away
+ */
+ if (len > MaxHeapTupleSize)
+ ereport(ERROR,
+ (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+ errmsg("row is too big: size %zu, maximum size %zu",
+ len, MaxHeapTupleSize)));
+
+ /* Compute desired extra freespace due to fillfactor option */
+ saveFreeSpace = RelationGetTargetPageFreeSpace(relation,
+ HEAP_DEFAULT_FILLFACTOR);
+
+ /*
+ * Since pages without tuples can still have line pointers, we consider
+ * pages "empty" when the unavailable space is slight. This threshold is
+ * somewhat arbitrary, but it should prevent most unnecessary relation
+ * extensions while inserting large tuples into low-fillfactor tables.
+ */
+ nearlyEmptyFreeSpace = MaxHeapTupleSize -
+ (MaxHeapTuplesPerPage / 8 * sizeof(ItemIdData));
+ if (len + saveFreeSpace > nearlyEmptyFreeSpace)
+ targetFreeSpace = Max(len, nearlyEmptyFreeSpace);
+ else
+ targetFreeSpace = len + saveFreeSpace;
+
+ if (otherBuffer != InvalidBuffer)
+ otherBlock = BufferGetBlockNumber(otherBuffer);
+ else
+ otherBlock = InvalidBlockNumber; /* just to keep compiler quiet */
+
+ /*
+ * We first try to put the tuple on the same page we last inserted a tuple
+ * on, as cached in the BulkInsertState or relcache entry. If that
+ * doesn't work, we ask the Free Space Map to locate a suitable page.
+ * Since the FSM's info might be out of date, we have to be prepared to
+ * loop around and retry multiple times. (To insure this isn't an infinite
+ * loop, we must update the FSM with the correct amount of free space on
+ * each page that proves not to be suitable.) If the FSM has no record of
+ * a page with enough free space, we give up and extend the relation.
+ *
+ * When use_fsm is false, we either put the tuple onto the existing target
+ * page or extend the relation.
+ */
+ if (bistate && bistate->current_buf != InvalidBuffer)
+ targetBlock = BufferGetBlockNumber(bistate->current_buf);
+ else
+ targetBlock = RelationGetTargetBlock(relation);
+
+ if (targetBlock == InvalidBlockNumber && use_fsm)
+ {
+ /*
+ * We have no cached target page, so ask the FSM for an initial
+ * target.
+ */
+ targetBlock = GetPageWithFreeSpace(relation, targetFreeSpace);
+ }
+
+ /*
+ * If the FSM knows nothing of the rel, try the last page before we give
+ * up and extend. This avoids one-tuple-per-page syndrome during
+ * bootstrapping or in a recently-started system.
+ */
+ if (targetBlock == InvalidBlockNumber)
+ {
+ BlockNumber nblocks = RelationGetNumberOfBlocks(relation);
+
+ if (nblocks > 0)
+ targetBlock = nblocks - 1;
+ }
+
+loop:
+ while (targetBlock != InvalidBlockNumber)
+ {
+ /*
+ * Read and exclusive-lock the target block, as well as the other
+ * block if one was given, taking suitable care with lock ordering and
+ * the possibility they are the same block.
+ *
+ * If the page-level all-visible flag is set, caller will need to
+ * clear both that and the corresponding visibility map bit. However,
+ * by the time we return, we'll have x-locked the buffer, and we don't
+ * want to do any I/O while in that state. So we check the bit here
+ * before taking the lock, and pin the page if it appears necessary.
+ * Checking without the lock creates a risk of getting the wrong
+ * answer, so we'll have to recheck after acquiring the lock.
+ */
+ if (otherBuffer == InvalidBuffer)
+ {
+ /* easy case */
+ buffer = ReadBufferBI(relation, targetBlock, RBM_NORMAL, bistate);
+ if (PageIsAllVisible(BufferGetPage(buffer)))
+ visibilitymap_pin(relation, targetBlock, vmbuffer);
+
+ /*
+ * If the page is empty, pin vmbuffer to set all_frozen bit later.
+ */
+ if ((options & HEAP_INSERT_FROZEN) &&
+ (PageGetMaxOffsetNumber(BufferGetPage(buffer)) == 0))
+ visibilitymap_pin(relation, targetBlock, vmbuffer);
+
+ LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+ }
+ else if (otherBlock == targetBlock)
+ {
+ /* also easy case */
+ buffer = otherBuffer;
+ if (PageIsAllVisible(BufferGetPage(buffer)))
+ visibilitymap_pin(relation, targetBlock, vmbuffer);
+ LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+ }
+ else if (otherBlock < targetBlock)
+ {
+ /* lock other buffer first */
+ buffer = ReadBuffer(relation, targetBlock);
+ if (PageIsAllVisible(BufferGetPage(buffer)))
+ visibilitymap_pin(relation, targetBlock, vmbuffer);
+ LockBuffer(otherBuffer, BUFFER_LOCK_EXCLUSIVE);
+ LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+ }
+ else
+ {
+ /* lock target buffer first */
+ buffer = ReadBuffer(relation, targetBlock);
+ if (PageIsAllVisible(BufferGetPage(buffer)))
+ visibilitymap_pin(relation, targetBlock, vmbuffer);
+ LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+ LockBuffer(otherBuffer, BUFFER_LOCK_EXCLUSIVE);
+ }
+
+ /*
+ * We now have the target page (and the other buffer, if any) pinned
+ * and locked. However, since our initial PageIsAllVisible checks
+ * were performed before acquiring the lock, the results might now be
+ * out of date, either for the selected victim buffer, or for the
+ * other buffer passed by the caller. In that case, we'll need to
+ * give up our locks, go get the pin(s) we failed to get earlier, and
+ * re-lock. That's pretty painful, but hopefully shouldn't happen
+ * often.
+ *
+ * Note that there's a small possibility that we didn't pin the page
+ * above but still have the correct page pinned anyway, either because
+ * we've already made a previous pass through this loop, or because
+ * caller passed us the right page anyway.
+ *
+ * Note also that it's possible that by the time we get the pin and
+ * retake the buffer locks, the visibility map bit will have been
+ * cleared by some other backend anyway. In that case, we'll have
+ * done a bit of extra work for no gain, but there's no real harm
+ * done.
+ */
+ if (otherBuffer == InvalidBuffer || targetBlock <= otherBlock)
+ GetVisibilityMapPins(relation, buffer, otherBuffer,
+ targetBlock, otherBlock, vmbuffer,
+ vmbuffer_other);
+ else
+ GetVisibilityMapPins(relation, otherBuffer, buffer,
+ otherBlock, targetBlock, vmbuffer_other,
+ vmbuffer);
+
+ /*
+ * Now we can check to see if there's enough free space here. If so,
+ * we're done.
+ */
+ page = BufferGetPage(buffer);
+
+ /*
+ * If necessary initialize page, it'll be used soon. We could avoid
+ * dirtying the buffer here, and rely on the caller to do so whenever
+ * it puts a tuple onto the page, but there seems not much benefit in
+ * doing so.
+ */
+ if (PageIsNew(page))
+ {
+ PageInit(page, BufferGetPageSize(buffer), 0);
+ MarkBufferDirty(buffer);
+ }
+
+ pageFreeSpace = PageGetHeapFreeSpace(page);
+ if (targetFreeSpace <= pageFreeSpace)
+ {
+ /* use this page as future insert target, too */
+ RelationSetTargetBlock(relation, targetBlock);
+ return buffer;
+ }
+
+ /*
+ * Not enough space, so we must give up our page locks and pin (if
+ * any) and prepare to look elsewhere. We don't care which order we
+ * unlock the two buffers in, so this can be slightly simpler than the
+ * code above.
+ */
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ if (otherBuffer == InvalidBuffer)
+ ReleaseBuffer(buffer);
+ else if (otherBlock != targetBlock)
+ {
+ LockBuffer(otherBuffer, BUFFER_LOCK_UNLOCK);
+ ReleaseBuffer(buffer);
+ }
+
+ /* Without FSM, always fall out of the loop and extend */
+ if (!use_fsm)
+ break;
+
+ /*
+ * Update FSM as to condition of this page, and ask for another page
+ * to try.
+ */
+ targetBlock = RecordAndGetPageWithFreeSpace(relation,
+ targetBlock,
+ pageFreeSpace,
+ targetFreeSpace);
+ }
+
+ /*
+ * Have to extend the relation.
+ *
+ * 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(relation);
+
+ /*
+ * If we need the lock but are not able to acquire it immediately, we'll
+ * consider extending the relation by multiple blocks at a time to manage
+ * contention on the relation extension lock. However, this only makes
+ * sense if we're using the FSM; otherwise, there's no point.
+ */
+ if (needLock)
+ {
+ if (!use_fsm)
+ LockRelationForExtension(relation, ExclusiveLock);
+ else if (!ConditionalLockRelationForExtension(relation, ExclusiveLock))
+ {
+ /* Couldn't get the lock immediately; wait for it. */
+ LockRelationForExtension(relation, ExclusiveLock);
+
+ /*
+ * Check if some other backend has extended a block for us while
+ * we were waiting on the lock.
+ */
+ targetBlock = GetPageWithFreeSpace(relation, targetFreeSpace);
+
+ /*
+ * If some other waiter has already extended the relation, we
+ * don't need to do so; just use the existing freespace.
+ */
+ if (targetBlock != InvalidBlockNumber)
+ {
+ UnlockRelationForExtension(relation, ExclusiveLock);
+ goto loop;
+ }
+
+ /* Time to bulk-extend. */
+ RelationAddExtraBlocks(relation, bistate);
+ }
+ }
+
+ /*
+ * In addition to whatever extension we performed above, we always add at
+ * least one block to satisfy our own request.
+ *
+ * XXX This does an lseek - rather expensive - but at the moment it is the
+ * only way to accurately determine how many blocks are in a relation. Is
+ * it worth keeping an accurate file length in shared memory someplace,
+ * rather than relying on the kernel to do it for us?
+ */
+ buffer = ReadBufferBI(relation, P_NEW, RBM_ZERO_AND_LOCK, bistate);
+
+ /*
+ * We need to initialize the empty new page. Double-check that it really
+ * is empty (this should never happen, but if it does we don't want to
+ * risk wiping out valid data).
+ */
+ page = BufferGetPage(buffer);
+
+ if (!PageIsNew(page))
+ elog(ERROR, "page %u of relation \"%s\" should be empty but is not",
+ BufferGetBlockNumber(buffer),
+ RelationGetRelationName(relation));
+
+ PageInit(page, BufferGetPageSize(buffer), 0);
+ MarkBufferDirty(buffer);
+
+ /*
+ * The page is empty, pin vmbuffer to set all_frozen bit.
+ */
+ if (options & HEAP_INSERT_FROZEN)
+ {
+ Assert(PageGetMaxOffsetNumber(BufferGetPage(buffer)) == 0);
+ visibilitymap_pin(relation, BufferGetBlockNumber(buffer), vmbuffer);
+ }
+
+ /*
+ * Release the file-extension lock; it's now OK for someone else to extend
+ * the relation some more.
+ */
+ if (needLock)
+ UnlockRelationForExtension(relation, ExclusiveLock);
+
+ /*
+ * Lock the other buffer. It's guaranteed to be of a lower page number
+ * than the new page. To conform with the deadlock prevent rules, we ought
+ * to lock otherBuffer first, but that would give other backends a chance
+ * to put tuples on our page. To reduce the likelihood of that, attempt to
+ * lock the other buffer conditionally, that's very likely to work.
+ * Otherwise we need to lock buffers in the correct order, and retry if
+ * the space has been used in the mean time.
+ *
+ * Alternatively, we could acquire the lock on otherBuffer before
+ * extending the relation, but that'd require holding the lock while
+ * performing IO, which seems worse than an unlikely retry.
+ */
+ if (otherBuffer != InvalidBuffer)
+ {
+ Assert(otherBuffer != buffer);
+ targetBlock = BufferGetBlockNumber(buffer);
+ Assert(targetBlock > otherBlock);
+
+ if (unlikely(!ConditionalLockBuffer(otherBuffer)))
+ {
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ LockBuffer(otherBuffer, BUFFER_LOCK_EXCLUSIVE);
+ LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
+
+ /*
+ * Because the buffers were unlocked for a while, it's possible,
+ * although unlikely, that an all-visible flag became set or that
+ * somebody used up the available space in the new page. We can
+ * use GetVisibilityMapPins to deal with the first case. In the
+ * second case, just retry from start.
+ */
+ GetVisibilityMapPins(relation, otherBuffer, buffer,
+ otherBlock, targetBlock, vmbuffer_other,
+ vmbuffer);
+
+ if (len > PageGetHeapFreeSpace(page))
+ {
+ LockBuffer(otherBuffer, BUFFER_LOCK_UNLOCK);
+ UnlockReleaseBuffer(buffer);
+
+ goto loop;
+ }
+ }
+ }
+
+ if (len > PageGetHeapFreeSpace(page))
+ {
+ /* We should not get here given the test at the top */
+ elog(PANIC, "tuple is too big: size %zu", len);
+ }
+
+ /*
+ * Remember the new page as our target for future insertions.
+ *
+ * XXX should we enter the new page into the free space map immediately,
+ * or just keep it for this backend's exclusive use in the short run
+ * (until VACUUM sees it)? Seems to depend on whether you expect the
+ * current backend to make more insertions or not, which is probably a
+ * good bet most of the time. So for now, don't add it to FSM yet.
+ */
+ RelationSetTargetBlock(relation, BufferGetBlockNumber(buffer));
+
+ return buffer;
+}