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Diffstat (limited to 'src/backend/access/heap/hio.c')
| -rw-r--r-- | src/backend/access/heap/hio.c | 886 |
1 files changed, 886 insertions, 0 deletions
diff --git a/src/backend/access/heap/hio.c b/src/backend/access/heap/hio.c new file mode 100644 index 0000000..ccc4c69 --- /dev/null +++ b/src/backend/access/heap/hio.c @@ -0,0 +1,886 @@ +/*------------------------------------------------------------------------- + * + * hio.c + * POSTGRES heap access method input/output code. + * + * Portions Copyright (c) 1996-2023, 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. + * + * To avoid complexity in the callers, either buffer1 or buffer2 may be + * InvalidBuffer if only one buffer is involved. For the same reason, block2 + * may be smaller than block1. + * + * Returns whether buffer locks were temporarily released. + */ +static bool +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; + bool released_locks = false; + + /* + * Swap buffers around to handle case of a single block/buffer, and to + * handle if lock ordering rules require to lock block2 first. + */ + if (!BufferIsValid(buffer1) || + (BufferIsValid(buffer2) && block1 > block2)) + { + Buffer tmpbuf = buffer1; + Buffer *tmpvmbuf = vmbuffer1; + BlockNumber tmpblock = block1; + + buffer1 = buffer2; + vmbuffer1 = vmbuffer2; + block1 = block2; + + buffer2 = tmpbuf; + vmbuffer2 = tmpvmbuf; + block2 = tmpblock; + } + + 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) + break; + + /* We must unlock both buffers before doing any I/O. */ + released_locks = true; + 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; + } + + return released_locks; +} + +/* + * Extend the relation. By multiple pages, if beneficial. + * + * If the caller needs multiple pages (num_pages > 1), we always try to extend + * by at least that much. + * + * If there is contention on the extension lock, we don't just extend "for + * ourselves", but we try to help others. We can do so by adding empty pages + * into the FSM. Typically there is no contention when we can't use the FSM. + * + * We do have to limit the number of pages to extend by to some value, as the + * buffers for all the extended pages need to, temporarily, be pinned. For now + * we define MAX_BUFFERS_TO_EXTEND_BY to be 64 buffers, it's hard to see + * benefits with higher numbers. This partially is because copyfrom.c's + * MAX_BUFFERED_TUPLES / MAX_BUFFERED_BYTES prevents larger multi_inserts. + * + * Returns a buffer for a newly extended block. If possible, the buffer is + * returned exclusively locked. *did_unlock is set to true if the lock had to + * be released, false otherwise. + * + * + * XXX: It would likely be beneficial for some workloads to extend more + * aggressively, e.g. using a heuristic based on the relation size. + */ +static Buffer +RelationAddBlocks(Relation relation, BulkInsertState bistate, + int num_pages, bool use_fsm, bool *did_unlock) +{ +#define MAX_BUFFERS_TO_EXTEND_BY 64 + Buffer victim_buffers[MAX_BUFFERS_TO_EXTEND_BY]; + BlockNumber first_block = InvalidBlockNumber; + BlockNumber last_block = InvalidBlockNumber; + uint32 extend_by_pages; + uint32 not_in_fsm_pages; + Buffer buffer; + Page page; + + /* + * Determine by how many pages to try to extend by. + */ + if (bistate == NULL && !use_fsm) + { + /* + * If we have neither bistate, nor can use the FSM, we can't bulk + * extend - there'd be no way to find the additional pages. + */ + extend_by_pages = 1; + } + else + { + uint32 waitcount; + + /* + * Try to extend at least by the number of pages the caller needs. We + * can remember the additional pages (either via FSM or bistate). + */ + extend_by_pages = num_pages; + + if (!RELATION_IS_LOCAL(relation)) + waitcount = RelationExtensionLockWaiterCount(relation); + else + waitcount = 0; + + /* + * Multiply the number of pages to extend by the number of waiters. Do + * this even if we're not using the FSM, as it still relieves + * contention, by deferring the next time this backend needs to + * extend. In that case the extended pages will be found via + * bistate->next_free. + */ + extend_by_pages += extend_by_pages * waitcount; + + /* --- + * If we previously extended using the same bistate, it's very likely + * we'll extend some more. Try to extend by as many pages as + * before. This can be important for performance for several reasons, + * including: + * + * - It prevents mdzeroextend() switching between extending the + * relation in different ways, which is inefficient for some + * filesystems. + * + * - Contention is often intermittent. Even if we currently don't see + * other waiters (see above), extending by larger amounts can + * prevent future contention. + * --- + */ + if (bistate) + extend_by_pages = Max(extend_by_pages, bistate->already_extended_by); + + /* + * Can't extend by more than MAX_BUFFERS_TO_EXTEND_BY, we need to pin + * them all concurrently. + */ + extend_by_pages = Min(extend_by_pages, MAX_BUFFERS_TO_EXTEND_BY); + } + + /* + * How many of the extended pages should be entered into the FSM? + * + * If we have a bistate, only enter pages that we don't need ourselves + * into the FSM. Otherwise every other backend will immediately try to + * use the pages this backend needs for itself, causing unnecessary + * contention. If we don't have a bistate, we can't avoid the FSM. + * + * Never enter the page returned into the FSM, we'll immediately use it. + */ + if (num_pages > 1 && bistate == NULL) + not_in_fsm_pages = 1; + else + not_in_fsm_pages = num_pages; + + /* prepare to put another buffer into the bistate */ + if (bistate && bistate->current_buf != InvalidBuffer) + { + ReleaseBuffer(bistate->current_buf); + bistate->current_buf = InvalidBuffer; + } + + /* + * Extend the relation. We ask for the first returned page to be locked, + * so that we are sure that nobody has inserted into the page + * concurrently. + * + * With the current MAX_BUFFERS_TO_EXTEND_BY there's no danger of + * [auto]vacuum trying to truncate later pages as REL_TRUNCATE_MINIMUM is + * way larger. + */ + first_block = ExtendBufferedRelBy(BMR_REL(relation), MAIN_FORKNUM, + bistate ? bistate->strategy : NULL, + EB_LOCK_FIRST, + extend_by_pages, + victim_buffers, + &extend_by_pages); + buffer = victim_buffers[0]; /* the buffer the function will return */ + last_block = first_block + (extend_by_pages - 1); + Assert(first_block == BufferGetBlockNumber(buffer)); + + /* + * Relation is now extended. Initialize the page. We do this here, before + * potentially releasing the lock on the page, because it allows us to + * double check that the page contents are 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", + first_block, + RelationGetRelationName(relation)); + + PageInit(page, BufferGetPageSize(buffer), 0); + MarkBufferDirty(buffer); + + /* + * If we decided to put pages into the FSM, release the buffer lock (but + * not pin), we don't want to do IO while holding a buffer lock. This will + * necessitate a bit more extensive checking in our caller. + */ + if (use_fsm && not_in_fsm_pages < extend_by_pages) + { + LockBuffer(buffer, BUFFER_LOCK_UNLOCK); + *did_unlock = true; + } + else + *did_unlock = false; + + /* + * Relation is now extended. Release pins on all buffers, except for the + * first (which we'll return). If we decided to put pages into the FSM, + * we can do that as part of the same loop. + */ + for (uint32 i = 1; i < extend_by_pages; i++) + { + BlockNumber curBlock = first_block + i; + + Assert(curBlock == BufferGetBlockNumber(victim_buffers[i])); + Assert(BlockNumberIsValid(curBlock)); + + ReleaseBuffer(victim_buffers[i]); + + if (use_fsm && i >= not_in_fsm_pages) + { + Size freespace = BufferGetPageSize(victim_buffers[i]) - + SizeOfPageHeaderData; + + RecordPageWithFreeSpace(relation, curBlock, freespace); + } + } + + if (use_fsm && not_in_fsm_pages < extend_by_pages) + { + BlockNumber first_fsm_block = first_block + not_in_fsm_pages; + + FreeSpaceMapVacuumRange(relation, first_fsm_block, last_block); + } + + if (bistate) + { + /* + * Remember the additional pages we extended by, so we later can use + * them without looking into the FSM. + */ + if (extend_by_pages > 1) + { + bistate->next_free = first_block + 1; + bistate->last_free = last_block; + } + else + { + bistate->next_free = InvalidBlockNumber; + bistate->last_free = InvalidBlockNumber; + } + + /* maintain bistate->current_buf */ + IncrBufferRefCount(buffer); + bistate->current_buf = buffer; + bistate->already_extended_by += extend_by_pages; + } + + return buffer; +#undef MAX_BUFFERS_TO_EXTEND_BY +} + +/* + * RelationGetBufferForTuple + * + * Returns pinned and exclusive-locked buffer of a page in given relation + * with free space >= given len. + * + * If num_pages is > 1, we will try to extend the relation by at least that + * many pages when we decide to extend the relation. This is more efficient + * for callers that know they will need multiple pages + * (e.g. heap_multi_insert()). + * + * 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, + int num_pages) +{ + 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 unlockedTargetBuffer; + bool recheckVmPins; + + len = MAXALIGN(len); /* be conservative */ + + /* if the caller doesn't know by how many pages to extend, extend by 1 */ + if (num_pages <= 0) + num_pages = 1; + + /* 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 ensure 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. + */ + GetVisibilityMapPins(relation, buffer, otherBuffer, + targetBlock, otherBlock, vmbuffer, + vmbuffer_other); + + /* + * 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); + } + + /* Is there an ongoing bulk extension? */ + if (bistate && bistate->next_free != InvalidBlockNumber) + { + Assert(bistate->next_free <= bistate->last_free); + + /* + * We bulk extended the relation before, and there are still some + * unused pages from that extension, so we don't need to look in + * the FSM for a new page. But do record the free space from the + * last page, somebody might insert narrower tuples later. + */ + if (use_fsm) + RecordPageWithFreeSpace(relation, targetBlock, pageFreeSpace); + + targetBlock = bistate->next_free; + if (bistate->next_free >= bistate->last_free) + { + bistate->next_free = InvalidBlockNumber; + bistate->last_free = InvalidBlockNumber; + } + else + bistate->next_free++; + } + else if (!use_fsm) + { + /* Without FSM, always fall out of the loop and extend */ + break; + } + else + { + /* + * 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 */ + buffer = RelationAddBlocks(relation, bistate, num_pages, use_fsm, + &unlockedTargetBuffer); + + targetBlock = BufferGetBlockNumber(buffer); + page = BufferGetPage(buffer); + + /* + * The page is empty, pin vmbuffer to set all_frozen bit. We don't want to + * do IO while the buffer is locked, so we unlock the page first if IO is + * needed (necessitating checks below). + */ + if (options & HEAP_INSERT_FROZEN) + { + Assert(PageGetMaxOffsetNumber(page) == 0); + + if (!visibilitymap_pin_ok(targetBlock, *vmbuffer)) + { + if (!unlockedTargetBuffer) + LockBuffer(buffer, BUFFER_LOCK_UNLOCK); + unlockedTargetBuffer = true; + visibilitymap_pin(relation, targetBlock, vmbuffer); + } + } + + /* + * Reacquire locks if necessary. + * + * If the target buffer was unlocked above, or is unlocked while + * reacquiring the lock on otherBuffer below, it's unlikely, but possible, + * that another backend used space on this page. We check for that below, + * and retry if necessary. + */ + recheckVmPins = false; + if (unlockedTargetBuffer) + { + /* released lock on target buffer above */ + if (otherBuffer != InvalidBuffer) + LockBuffer(otherBuffer, BUFFER_LOCK_EXCLUSIVE); + LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); + recheckVmPins = true; + } + else if (otherBuffer != InvalidBuffer) + { + /* + * We did not release the target buffer, and otherBuffer is valid, + * need to 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. + * + * 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. + */ + Assert(otherBuffer != buffer); + Assert(targetBlock > otherBlock); + + if (unlikely(!ConditionalLockBuffer(otherBuffer))) + { + unlockedTargetBuffer = true; + LockBuffer(buffer, BUFFER_LOCK_UNLOCK); + LockBuffer(otherBuffer, BUFFER_LOCK_EXCLUSIVE); + LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE); + } + recheckVmPins = true; + } + + /* + * If one of the buffers was unlocked (always the case if otherBuffer is + * valid), it's possible, although unlikely, that an all-visible flag + * became set. We can use GetVisibilityMapPins to deal with that. It's + * possible that GetVisibilityMapPins() might need to temporarily release + * buffer locks, in which case we'll need to check if there's still enough + * space on the page below. + */ + if (recheckVmPins) + { + if (GetVisibilityMapPins(relation, otherBuffer, buffer, + otherBlock, targetBlock, vmbuffer_other, + vmbuffer)) + unlockedTargetBuffer = true; + } + + /* + * If the target buffer was temporarily unlocked since the relation + * extension, it's possible, although unlikely, that all the space on the + * page was already used. If so, we just retry from the start. If we + * didn't unlock, something has gone wrong if there's not enough space - + * the test at the top should have prevented reaching this case. + */ + pageFreeSpace = PageGetHeapFreeSpace(page); + if (len > pageFreeSpace) + { + if (unlockedTargetBuffer) + { + if (otherBuffer != InvalidBuffer) + LockBuffer(otherBuffer, BUFFER_LOCK_UNLOCK); + UnlockReleaseBuffer(buffer); + + goto loop; + } + 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, targetBlock); + + return buffer; +} |