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/*-------------------------------------------------------------------------
*
* ginvacuum.c
* delete & vacuum routines for the postgres GIN
*
*
* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/access/gin/ginvacuum.c
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/gin_private.h"
#include "access/ginxlog.h"
#include "access/xloginsert.h"
#include "commands/vacuum.h"
#include "miscadmin.h"
#include "postmaster/autovacuum.h"
#include "storage/indexfsm.h"
#include "storage/lmgr.h"
#include "storage/predicate.h"
#include "utils/memutils.h"
struct GinVacuumState
{
Relation index;
IndexBulkDeleteResult *result;
IndexBulkDeleteCallback callback;
void *callback_state;
GinState ginstate;
BufferAccessStrategy strategy;
MemoryContext tmpCxt;
};
/*
* Vacuums an uncompressed posting list. The size of the must can be specified
* in number of items (nitems).
*
* If none of the items need to be removed, returns NULL. Otherwise returns
* a new palloc'd array with the remaining items. The number of remaining
* items is returned in *nremaining.
*/
ItemPointer
ginVacuumItemPointers(GinVacuumState *gvs, ItemPointerData *items,
int nitem, int *nremaining)
{
int i,
remaining = 0;
ItemPointer tmpitems = NULL;
/*
* Iterate over TIDs array
*/
for (i = 0; i < nitem; i++)
{
if (gvs->callback(items + i, gvs->callback_state))
{
gvs->result->tuples_removed += 1;
if (!tmpitems)
{
/*
* First TID to be deleted: allocate memory to hold the
* remaining items.
*/
tmpitems = palloc(sizeof(ItemPointerData) * nitem);
memcpy(tmpitems, items, sizeof(ItemPointerData) * i);
}
}
else
{
gvs->result->num_index_tuples += 1;
if (tmpitems)
tmpitems[remaining] = items[i];
remaining++;
}
}
*nremaining = remaining;
return tmpitems;
}
/*
* Create a WAL record for vacuuming entry tree leaf page.
*/
static void
xlogVacuumPage(Relation index, Buffer buffer)
{
Page page = BufferGetPage(buffer);
XLogRecPtr recptr;
/* This is only used for entry tree leaf pages. */
Assert(!GinPageIsData(page));
Assert(GinPageIsLeaf(page));
if (!RelationNeedsWAL(index))
return;
/*
* Always create a full image, we don't track the changes on the page at
* any more fine-grained level. This could obviously be improved...
*/
XLogBeginInsert();
XLogRegisterBuffer(0, buffer, REGBUF_FORCE_IMAGE | REGBUF_STANDARD);
recptr = XLogInsert(RM_GIN_ID, XLOG_GIN_VACUUM_PAGE);
PageSetLSN(page, recptr);
}
typedef struct DataPageDeleteStack
{
struct DataPageDeleteStack *child;
struct DataPageDeleteStack *parent;
BlockNumber blkno; /* current block number */
Buffer leftBuffer; /* pinned and locked rightest non-deleted page
* on left */
bool isRoot;
} DataPageDeleteStack;
/*
* Delete a posting tree page.
*/
static void
ginDeletePage(GinVacuumState *gvs, BlockNumber deleteBlkno, BlockNumber leftBlkno,
BlockNumber parentBlkno, OffsetNumber myoff, bool isParentRoot)
{
Buffer dBuffer;
Buffer lBuffer;
Buffer pBuffer;
Page page,
parentPage;
BlockNumber rightlink;
/*
* This function MUST be called only if someone of parent pages hold
* exclusive cleanup lock. This guarantees that no insertions currently
* happen in this subtree. Caller also acquires Exclusive locks on
* deletable, parent and left pages.
*/
lBuffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, leftBlkno,
RBM_NORMAL, gvs->strategy);
dBuffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, deleteBlkno,
RBM_NORMAL, gvs->strategy);
pBuffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, parentBlkno,
RBM_NORMAL, gvs->strategy);
page = BufferGetPage(dBuffer);
rightlink = GinPageGetOpaque(page)->rightlink;
/*
* Any insert which would have gone on the leaf block will now go to its
* right sibling.
*/
PredicateLockPageCombine(gvs->index, deleteBlkno, rightlink);
START_CRIT_SECTION();
/* Unlink the page by changing left sibling's rightlink */
page = BufferGetPage(lBuffer);
GinPageGetOpaque(page)->rightlink = rightlink;
/* Delete downlink from parent */
parentPage = BufferGetPage(pBuffer);
#ifdef USE_ASSERT_CHECKING
do
{
PostingItem *tod = GinDataPageGetPostingItem(parentPage, myoff);
Assert(PostingItemGetBlockNumber(tod) == deleteBlkno);
} while (0);
#endif
GinPageDeletePostingItem(parentPage, myoff);
page = BufferGetPage(dBuffer);
/*
* we shouldn't change rightlink field to save workability of running
* search scan
*/
/*
* Mark page as deleted, and remember last xid which could know its
* address.
*/
GinPageSetDeleted(page);
GinPageSetDeleteXid(page, ReadNextTransactionId());
MarkBufferDirty(pBuffer);
MarkBufferDirty(lBuffer);
MarkBufferDirty(dBuffer);
if (RelationNeedsWAL(gvs->index))
{
XLogRecPtr recptr;
ginxlogDeletePage data;
/*
* We can't pass REGBUF_STANDARD for the deleted page, because we
* didn't set pd_lower on pre-9.4 versions. The page might've been
* binary-upgraded from an older version, and hence not have pd_lower
* set correctly. Ditto for the left page, but removing the item from
* the parent updated its pd_lower, so we know that's OK at this
* point.
*/
XLogBeginInsert();
XLogRegisterBuffer(0, dBuffer, 0);
XLogRegisterBuffer(1, pBuffer, REGBUF_STANDARD);
XLogRegisterBuffer(2, lBuffer, 0);
data.parentOffset = myoff;
data.rightLink = GinPageGetOpaque(page)->rightlink;
data.deleteXid = GinPageGetDeleteXid(page);
XLogRegisterData((char *) &data, sizeof(ginxlogDeletePage));
recptr = XLogInsert(RM_GIN_ID, XLOG_GIN_DELETE_PAGE);
PageSetLSN(page, recptr);
PageSetLSN(parentPage, recptr);
PageSetLSN(BufferGetPage(lBuffer), recptr);
}
ReleaseBuffer(pBuffer);
ReleaseBuffer(lBuffer);
ReleaseBuffer(dBuffer);
END_CRIT_SECTION();
gvs->result->pages_newly_deleted++;
gvs->result->pages_deleted++;
}
/*
* Scans posting tree and deletes empty pages. Caller must lock root page for
* cleanup. During scan path from root to current page is kept exclusively
* locked. Also keep left page exclusively locked, because ginDeletePage()
* needs it. If we try to relock left page later, it could deadlock with
* ginStepRight().
*/
static bool
ginScanToDelete(GinVacuumState *gvs, BlockNumber blkno, bool isRoot,
DataPageDeleteStack *parent, OffsetNumber myoff)
{
DataPageDeleteStack *me;
Buffer buffer;
Page page;
bool meDelete = false;
bool isempty;
if (isRoot)
{
me = parent;
}
else
{
if (!parent->child)
{
me = (DataPageDeleteStack *) palloc0(sizeof(DataPageDeleteStack));
me->parent = parent;
parent->child = me;
me->leftBuffer = InvalidBuffer;
}
else
me = parent->child;
}
buffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, blkno,
RBM_NORMAL, gvs->strategy);
if (!isRoot)
LockBuffer(buffer, GIN_EXCLUSIVE);
page = BufferGetPage(buffer);
Assert(GinPageIsData(page));
if (!GinPageIsLeaf(page))
{
OffsetNumber i;
me->blkno = blkno;
for (i = FirstOffsetNumber; i <= GinPageGetOpaque(page)->maxoff; i++)
{
PostingItem *pitem = GinDataPageGetPostingItem(page, i);
if (ginScanToDelete(gvs, PostingItemGetBlockNumber(pitem), false, me, i))
i--;
}
if (GinPageRightMost(page) && BufferIsValid(me->child->leftBuffer))
{
UnlockReleaseBuffer(me->child->leftBuffer);
me->child->leftBuffer = InvalidBuffer;
}
}
if (GinPageIsLeaf(page))
isempty = GinDataLeafPageIsEmpty(page);
else
isempty = GinPageGetOpaque(page)->maxoff < FirstOffsetNumber;
if (isempty)
{
/* we never delete the left- or rightmost branch */
if (BufferIsValid(me->leftBuffer) && !GinPageRightMost(page))
{
Assert(!isRoot);
ginDeletePage(gvs, blkno, BufferGetBlockNumber(me->leftBuffer),
me->parent->blkno, myoff, me->parent->isRoot);
meDelete = true;
}
}
if (!meDelete)
{
if (BufferIsValid(me->leftBuffer))
UnlockReleaseBuffer(me->leftBuffer);
me->leftBuffer = buffer;
}
else
{
if (!isRoot)
LockBuffer(buffer, GIN_UNLOCK);
ReleaseBuffer(buffer);
}
if (isRoot)
ReleaseBuffer(buffer);
return meDelete;
}
/*
* Scan through posting tree leafs, delete empty tuples. Returns true if there
* is at least one empty page.
*/
static bool
ginVacuumPostingTreeLeaves(GinVacuumState *gvs, BlockNumber blkno)
{
Buffer buffer;
Page page;
bool hasVoidPage = false;
MemoryContext oldCxt;
/* Find leftmost leaf page of posting tree and lock it in exclusive mode */
while (true)
{
PostingItem *pitem;
buffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, blkno,
RBM_NORMAL, gvs->strategy);
LockBuffer(buffer, GIN_SHARE);
page = BufferGetPage(buffer);
Assert(GinPageIsData(page));
if (GinPageIsLeaf(page))
{
LockBuffer(buffer, GIN_UNLOCK);
LockBuffer(buffer, GIN_EXCLUSIVE);
break;
}
Assert(PageGetMaxOffsetNumber(page) >= FirstOffsetNumber);
pitem = GinDataPageGetPostingItem(page, FirstOffsetNumber);
blkno = PostingItemGetBlockNumber(pitem);
Assert(blkno != InvalidBlockNumber);
UnlockReleaseBuffer(buffer);
}
/* Iterate all posting tree leaves using rightlinks and vacuum them */
while (true)
{
oldCxt = MemoryContextSwitchTo(gvs->tmpCxt);
ginVacuumPostingTreeLeaf(gvs->index, buffer, gvs);
MemoryContextSwitchTo(oldCxt);
MemoryContextReset(gvs->tmpCxt);
if (GinDataLeafPageIsEmpty(page))
hasVoidPage = true;
blkno = GinPageGetOpaque(page)->rightlink;
UnlockReleaseBuffer(buffer);
if (blkno == InvalidBlockNumber)
break;
buffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, blkno,
RBM_NORMAL, gvs->strategy);
LockBuffer(buffer, GIN_EXCLUSIVE);
page = BufferGetPage(buffer);
}
return hasVoidPage;
}
static void
ginVacuumPostingTree(GinVacuumState *gvs, BlockNumber rootBlkno)
{
if (ginVacuumPostingTreeLeaves(gvs, rootBlkno))
{
/*
* There is at least one empty page. So we have to rescan the tree
* deleting empty pages.
*/
Buffer buffer;
DataPageDeleteStack root,
*ptr,
*tmp;
buffer = ReadBufferExtended(gvs->index, MAIN_FORKNUM, rootBlkno,
RBM_NORMAL, gvs->strategy);
/*
* Lock posting tree root for cleanup to ensure there are no
* concurrent inserts.
*/
LockBufferForCleanup(buffer);
memset(&root, 0, sizeof(DataPageDeleteStack));
root.leftBuffer = InvalidBuffer;
root.isRoot = true;
ginScanToDelete(gvs, rootBlkno, true, &root, InvalidOffsetNumber);
ptr = root.child;
while (ptr)
{
tmp = ptr->child;
pfree(ptr);
ptr = tmp;
}
UnlockReleaseBuffer(buffer);
}
}
/*
* returns modified page or NULL if page isn't modified.
* Function works with original page until first change is occurred,
* then page is copied into temporary one.
*/
static Page
ginVacuumEntryPage(GinVacuumState *gvs, Buffer buffer, BlockNumber *roots, uint32 *nroot)
{
Page origpage = BufferGetPage(buffer),
tmppage;
OffsetNumber i,
maxoff = PageGetMaxOffsetNumber(origpage);
tmppage = origpage;
*nroot = 0;
for (i = FirstOffsetNumber; i <= maxoff; i++)
{
IndexTuple itup = (IndexTuple) PageGetItem(tmppage, PageGetItemId(tmppage, i));
if (GinIsPostingTree(itup))
{
/*
* store posting tree's roots for further processing, we can't
* vacuum it just now due to risk of deadlocks with scans/inserts
*/
roots[*nroot] = GinGetDownlink(itup);
(*nroot)++;
}
else if (GinGetNPosting(itup) > 0)
{
int nitems;
ItemPointer items_orig;
bool free_items_orig;
ItemPointer items;
/* Get list of item pointers from the tuple. */
if (GinItupIsCompressed(itup))
{
items_orig = ginPostingListDecode((GinPostingList *) GinGetPosting(itup), &nitems);
free_items_orig = true;
}
else
{
items_orig = (ItemPointer) GinGetPosting(itup);
nitems = GinGetNPosting(itup);
free_items_orig = false;
}
/* Remove any items from the list that need to be vacuumed. */
items = ginVacuumItemPointers(gvs, items_orig, nitems, &nitems);
if (free_items_orig)
pfree(items_orig);
/* If any item pointers were removed, recreate the tuple. */
if (items)
{
OffsetNumber attnum;
Datum key;
GinNullCategory category;
GinPostingList *plist;
int plistsize;
if (nitems > 0)
{
plist = ginCompressPostingList(items, nitems, GinMaxItemSize, NULL);
plistsize = SizeOfGinPostingList(plist);
}
else
{
plist = NULL;
plistsize = 0;
}
/*
* if we already created a temporary page, make changes in
* place
*/
if (tmppage == origpage)
{
/*
* On first difference, create a temporary copy of the
* page and copy the tuple's posting list to it.
*/
tmppage = PageGetTempPageCopy(origpage);
/* set itup pointer to new page */
itup = (IndexTuple) PageGetItem(tmppage, PageGetItemId(tmppage, i));
}
attnum = gintuple_get_attrnum(&gvs->ginstate, itup);
key = gintuple_get_key(&gvs->ginstate, itup, &category);
itup = GinFormTuple(&gvs->ginstate, attnum, key, category,
(char *) plist, plistsize,
nitems, true);
if (plist)
pfree(plist);
PageIndexTupleDelete(tmppage, i);
if (PageAddItem(tmppage, (Item) itup, IndexTupleSize(itup), i, false, false) != i)
elog(ERROR, "failed to add item to index page in \"%s\"",
RelationGetRelationName(gvs->index));
pfree(itup);
pfree(items);
}
}
}
return (tmppage == origpage) ? NULL : tmppage;
}
IndexBulkDeleteResult *
ginbulkdelete(IndexVacuumInfo *info, IndexBulkDeleteResult *stats,
IndexBulkDeleteCallback callback, void *callback_state)
{
Relation index = info->index;
BlockNumber blkno = GIN_ROOT_BLKNO;
GinVacuumState gvs;
Buffer buffer;
BlockNumber rootOfPostingTree[BLCKSZ / (sizeof(IndexTupleData) + sizeof(ItemId))];
uint32 nRoot;
gvs.tmpCxt = AllocSetContextCreate(CurrentMemoryContext,
"Gin vacuum temporary context",
ALLOCSET_DEFAULT_SIZES);
gvs.index = index;
gvs.callback = callback;
gvs.callback_state = callback_state;
gvs.strategy = info->strategy;
initGinState(&gvs.ginstate, index);
/* first time through? */
if (stats == NULL)
{
/* Yes, so initialize stats to zeroes */
stats = (IndexBulkDeleteResult *) palloc0(sizeof(IndexBulkDeleteResult));
/*
* and cleanup any pending inserts
*/
ginInsertCleanup(&gvs.ginstate, !IsAutoVacuumWorkerProcess(),
false, true, stats);
}
/* we'll re-count the tuples each time */
stats->num_index_tuples = 0;
gvs.result = stats;
buffer = ReadBufferExtended(index, MAIN_FORKNUM, blkno,
RBM_NORMAL, info->strategy);
/* find leaf page */
for (;;)
{
Page page = BufferGetPage(buffer);
IndexTuple itup;
LockBuffer(buffer, GIN_SHARE);
Assert(!GinPageIsData(page));
if (GinPageIsLeaf(page))
{
LockBuffer(buffer, GIN_UNLOCK);
LockBuffer(buffer, GIN_EXCLUSIVE);
if (blkno == GIN_ROOT_BLKNO && !GinPageIsLeaf(page))
{
LockBuffer(buffer, GIN_UNLOCK);
continue; /* check it one more */
}
break;
}
Assert(PageGetMaxOffsetNumber(page) >= FirstOffsetNumber);
itup = (IndexTuple) PageGetItem(page, PageGetItemId(page, FirstOffsetNumber));
blkno = GinGetDownlink(itup);
Assert(blkno != InvalidBlockNumber);
UnlockReleaseBuffer(buffer);
buffer = ReadBufferExtended(index, MAIN_FORKNUM, blkno,
RBM_NORMAL, info->strategy);
}
/* right now we found leftmost page in entry's BTree */
for (;;)
{
Page page = BufferGetPage(buffer);
Page resPage;
uint32 i;
Assert(!GinPageIsData(page));
resPage = ginVacuumEntryPage(&gvs, buffer, rootOfPostingTree, &nRoot);
blkno = GinPageGetOpaque(page)->rightlink;
if (resPage)
{
START_CRIT_SECTION();
PageRestoreTempPage(resPage, page);
MarkBufferDirty(buffer);
xlogVacuumPage(gvs.index, buffer);
UnlockReleaseBuffer(buffer);
END_CRIT_SECTION();
}
else
{
UnlockReleaseBuffer(buffer);
}
vacuum_delay_point();
for (i = 0; i < nRoot; i++)
{
ginVacuumPostingTree(&gvs, rootOfPostingTree[i]);
vacuum_delay_point();
}
if (blkno == InvalidBlockNumber) /* rightmost page */
break;
buffer = ReadBufferExtended(index, MAIN_FORKNUM, blkno,
RBM_NORMAL, info->strategy);
LockBuffer(buffer, GIN_EXCLUSIVE);
}
MemoryContextDelete(gvs.tmpCxt);
return gvs.result;
}
IndexBulkDeleteResult *
ginvacuumcleanup(IndexVacuumInfo *info, IndexBulkDeleteResult *stats)
{
Relation index = info->index;
bool needLock;
BlockNumber npages,
blkno;
BlockNumber totFreePages;
GinState ginstate;
GinStatsData idxStat;
/*
* In an autovacuum analyze, we want to clean up pending insertions.
* Otherwise, an ANALYZE-only call is a no-op.
*/
if (info->analyze_only)
{
if (IsAutoVacuumWorkerProcess())
{
initGinState(&ginstate, index);
ginInsertCleanup(&ginstate, false, true, true, stats);
}
return stats;
}
/*
* Set up all-zero stats and cleanup pending inserts if ginbulkdelete
* wasn't called
*/
if (stats == NULL)
{
stats = (IndexBulkDeleteResult *) palloc0(sizeof(IndexBulkDeleteResult));
initGinState(&ginstate, index);
ginInsertCleanup(&ginstate, !IsAutoVacuumWorkerProcess(),
false, true, stats);
}
memset(&idxStat, 0, sizeof(idxStat));
/*
* XXX we always report the heap tuple count as the number of index
* entries. This is bogus if the index is partial, but it's real hard to
* tell how many distinct heap entries are referenced by a GIN index.
*/
stats->num_index_tuples = Max(info->num_heap_tuples, 0);
stats->estimated_count = info->estimated_count;
/*
* Need lock unless it's local to this backend.
*/
needLock = !RELATION_IS_LOCAL(index);
if (needLock)
LockRelationForExtension(index, ExclusiveLock);
npages = RelationGetNumberOfBlocks(index);
if (needLock)
UnlockRelationForExtension(index, ExclusiveLock);
totFreePages = 0;
for (blkno = GIN_ROOT_BLKNO; blkno < npages; blkno++)
{
Buffer buffer;
Page page;
vacuum_delay_point();
buffer = ReadBufferExtended(index, MAIN_FORKNUM, blkno,
RBM_NORMAL, info->strategy);
LockBuffer(buffer, GIN_SHARE);
page = (Page) BufferGetPage(buffer);
if (GinPageIsRecyclable(page))
{
Assert(blkno != GIN_ROOT_BLKNO);
RecordFreeIndexPage(index, blkno);
totFreePages++;
}
else if (GinPageIsData(page))
{
idxStat.nDataPages++;
}
else if (!GinPageIsList(page))
{
idxStat.nEntryPages++;
if (GinPageIsLeaf(page))
idxStat.nEntries += PageGetMaxOffsetNumber(page);
}
UnlockReleaseBuffer(buffer);
}
/* Update the metapage with accurate page and entry counts */
idxStat.nTotalPages = npages;
ginUpdateStats(info->index, &idxStat, false);
/* Finally, vacuum the FSM */
IndexFreeSpaceMapVacuum(info->index);
stats->pages_free = totFreePages;
if (needLock)
LockRelationForExtension(index, ExclusiveLock);
stats->num_pages = RelationGetNumberOfBlocks(index);
if (needLock)
UnlockRelationForExtension(index, ExclusiveLock);
return stats;
}
/*
* Return whether Page can safely be recycled.
*/
bool
GinPageIsRecyclable(Page page)
{
TransactionId delete_xid;
if (PageIsNew(page))
return true;
if (!GinPageIsDeleted(page))
return false;
delete_xid = GinPageGetDeleteXid(page);
if (!TransactionIdIsValid(delete_xid))
return true;
/*
* If no backend still could view delete_xid as in running, all scans
* concurrent with ginDeletePage() must have finished.
*/
return GlobalVisCheckRemovableXid(NULL, delete_xid);
}
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