bufpage.c File Reference

#include "postgres.h"
#include "access/htup_details.h"
#include "access/itup.h"
#include "access/xlog.h"
#include "pgstat.h"
#include "storage/checksum.h"
#include "utils/memdebug.h"
#include "utils/memutils.h"

Include dependency graph for bufpage.c:

Go to the source code of this file.

Data Structures
struct	itemIdCompactData

Typedefs
typedef struct itemIdCompactData	itemIdCompactData
typedef itemIdCompactData *	itemIdCompact

Functions
void	PageInit (Page page, Size pageSize, Size specialSize)
bool	PageIsVerifiedExtended (PageData *page, BlockNumber blkno, int flags)
OffsetNumber	PageAddItemExtended (Page page, Item item, Size size, OffsetNumber offsetNumber, int flags)
Page	PageGetTempPage (const PageData *page)
Page	PageGetTempPageCopy (const PageData *page)
Page	PageGetTempPageCopySpecial (const PageData *page)
void	PageRestoreTempPage (Page tempPage, Page oldPage)
static void	compactify_tuples (itemIdCompact itemidbase, int nitems, Page page, bool presorted)
void	PageRepairFragmentation (Page page)
void	PageTruncateLinePointerArray (Page page)
Size	PageGetFreeSpace (const PageData *page)
Size	PageGetFreeSpaceForMultipleTuples (const PageData *page, int ntups)
Size	PageGetExactFreeSpace (const PageData *page)
Size	PageGetHeapFreeSpace (const PageData *page)
void	PageIndexTupleDelete (Page page, OffsetNumber offnum)
void	PageIndexMultiDelete (Page page, OffsetNumber *itemnos, int nitems)
void	PageIndexTupleDeleteNoCompact (Page page, OffsetNumber offnum)
bool	PageIndexTupleOverwrite (Page page, OffsetNumber offnum, Item newtup, Size newsize)
char *	PageSetChecksumCopy (Page page, BlockNumber blkno)
void	PageSetChecksumInplace (Page page, BlockNumber blkno)

Variables
bool	ignore_checksum_failure = false

Typedef Documentation

itemIdCompact

typedef itemIdCompactData* itemIdCompact

Definition at line 432 of file bufpage.c.

itemIdCompactData

typedef struct itemIdCompactData itemIdCompactData

Function Documentation

compactify_tuples()

static void compactify_tuples ( itemIdCompact  itemidbase, int  nitems, Page  page, bool  presorted  )

static

Definition at line 463 of file bufpage.c.

{
    PageHeader  phdr = (PageHeader) page;
    Offset      upper;
    Offset      copy_tail;
    Offset      copy_head;
    itemIdCompact itemidptr;
    int         i;
 
    /* Code within will not work correctly if nitems == 0 */
    Assert(nitems > 0);
 
    if (presorted)
    {
 
#ifdef USE_ASSERT_CHECKING
        {
            /*
             * Verify we've not gotten any new callers that are incorrectly
             * passing a true presorted value.
             */
            Offset      lastoff = phdr->pd_special;
 
            for (i = 0; i < nitems; i++)
            {
                itemidptr = &itemidbase[i];
 
                Assert(lastoff > itemidptr->itemoff);
 
                lastoff = itemidptr->itemoff;
            }
        }
#endif                          /* USE_ASSERT_CHECKING */
 
        /*
         * 'itemidbase' is already in the optimal order, i.e, lower item
         * pointers have a higher offset.  This allows us to memmove() the
         * tuples up to the end of the page without having to worry about
         * overwriting other tuples that have not been moved yet.
         *
         * There's a good chance that there are tuples already right at the
         * end of the page that we can simply skip over because they're
         * already in the correct location within the page.  We'll do that
         * first...
         */
        upper = phdr->pd_special;
        i = 0;
        do
        {
            itemidptr = &itemidbase[i];
            if (upper != itemidptr->itemoff + itemidptr->alignedlen)
                break;
            upper -= itemidptr->alignedlen;
 
            i++;
        } while (i < nitems);
 
        /*
         * Now that we've found the first tuple that needs to be moved, we can
         * do the tuple compactification.  We try and make the least number of
         * memmove() calls and only call memmove() when there's a gap.  When
         * we see a gap we just move all tuples after the gap up until the
         * point of the last move operation.
         */
        copy_tail = copy_head = itemidptr->itemoff + itemidptr->alignedlen;
        for (; i < nitems; i++)
        {
            ItemId      lp;
 
            itemidptr = &itemidbase[i];
            lp = PageGetItemId(page, itemidptr->offsetindex + 1);
 
            if (copy_head != itemidptr->itemoff + itemidptr->alignedlen)
            {
                memmove((char *) page + upper,
                        page + copy_head,
                        copy_tail - copy_head);
 
                /*
                 * We've now moved all tuples already seen, but not the
                 * current tuple, so we set the copy_tail to the end of this
                 * tuple so it can be moved in another iteration of the loop.
                 */
                copy_tail = itemidptr->itemoff + itemidptr->alignedlen;
            }
            /* shift the target offset down by the length of this tuple */
            upper -= itemidptr->alignedlen;
            /* point the copy_head to the start of this tuple */
            copy_head = itemidptr->itemoff;
 
            /* update the line pointer to reference the new offset */
            lp->lp_off = upper;
        }
 
        /* move the remaining tuples. */
        memmove((char *) page + upper,
                page + copy_head,
                copy_tail - copy_head);
    }
    else
    {
        PGAlignedBlock scratch;
        char       *scratchptr = scratch.data;
 
        /*
         * Non-presorted case:  The tuples in the itemidbase array may be in
         * any order.  So, in order to move these to the end of the page we
         * must make a temp copy of each tuple that needs to be moved before
         * we copy them back into the page at the new offset.
         *
         * If a large percentage of tuples have been pruned (>75%) then we'll
         * copy these into the temp buffer tuple-by-tuple, otherwise, we'll
         * just do a single memcpy() for all tuples that need to be moved.
         * When so many tuples have been removed there's likely to be a lot of
         * gaps and it's unlikely that many non-movable tuples remain at the
         * end of the page.
         */
        if (nitems < PageGetMaxOffsetNumber(page) / 4)
        {
            i = 0;
            do
            {
                itemidptr = &itemidbase[i];
                memcpy(scratchptr + itemidptr->itemoff, page + itemidptr->itemoff,
                       itemidptr->alignedlen);
                i++;
            } while (i < nitems);
 
            /* Set things up for the compactification code below */
            i = 0;
            itemidptr = &itemidbase[0];
            upper = phdr->pd_special;
        }
        else
        {
            upper = phdr->pd_special;
 
            /*
             * Many tuples are likely to already be in the correct location.
             * There's no need to copy these into the temp buffer.  Instead
             * we'll just skip forward in the itemidbase array to the position
             * that we do need to move tuples from so that the code below just
             * leaves these ones alone.
             */
            i = 0;
            do
            {
                itemidptr = &itemidbase[i];
                if (upper != itemidptr->itemoff + itemidptr->alignedlen)
                    break;
                upper -= itemidptr->alignedlen;
 
                i++;
            } while (i < nitems);
 
            /* Copy all tuples that need to be moved into the temp buffer */
            memcpy(scratchptr + phdr->pd_upper,
                   page + phdr->pd_upper,
                   upper - phdr->pd_upper);
        }
 
        /*
         * Do the tuple compactification.  itemidptr is already pointing to
         * the first tuple that we're going to move.  Here we collapse the
         * memcpy calls for adjacent tuples into a single call.  This is done
         * by delaying the memcpy call until we find a gap that needs to be
         * closed.
         */
        copy_tail = copy_head = itemidptr->itemoff + itemidptr->alignedlen;
        for (; i < nitems; i++)
        {
            ItemId      lp;
 
            itemidptr = &itemidbase[i];
            lp = PageGetItemId(page, itemidptr->offsetindex + 1);
 
            /* copy pending tuples when we detect a gap */
            if (copy_head != itemidptr->itemoff + itemidptr->alignedlen)
            {
                memcpy((char *) page + upper,
                       scratchptr + copy_head,
                       copy_tail - copy_head);
 
                /*
                 * We've now copied all tuples already seen, but not the
                 * current tuple, so we set the copy_tail to the end of this
                 * tuple.
                 */
                copy_tail = itemidptr->itemoff + itemidptr->alignedlen;
            }
            /* shift the target offset down by the length of this tuple */
            upper -= itemidptr->alignedlen;
            /* point the copy_head to the start of this tuple */
            copy_head = itemidptr->itemoff;
 
            /* update the line pointer to reference the new offset */
            lp->lp_off = upper;
        }
 
        /* Copy the remaining chunk */
        memcpy((char *) page + upper,
               scratchptr + copy_head,
               copy_tail - copy_head);
    }
 
    phdr->pd_upper = upper;
}

References itemIdCompactData::alignedlen, Assert(), PGAlignedBlock::data, i, itemIdCompactData::itemoff, ItemIdData::lp_off, nitems, itemIdCompactData::offsetindex, PageGetItemId(), PageGetMaxOffsetNumber(), PageHeaderData::pd_special, PageHeaderData::pd_upper, and upper().

Referenced by PageIndexMultiDelete(), and PageRepairFragmentation().

PageAddItemExtended()

OffsetNumber PageAddItemExtended	(	Page	page,
		Item	item,
		Size	size,
		OffsetNumber	offsetNumber,
		int	flags
	)

Definition at line 183 of file bufpage.c.

{
    PageHeader  phdr = (PageHeader) page;
    Size        alignedSize;
    int         lower;
    int         upper;
    ItemId      itemId;
    OffsetNumber limit;
    bool        needshuffle = false;
 
    /*
     * Be wary about corrupted page pointers
     */
    if (phdr->pd_lower < SizeOfPageHeaderData ||
        phdr->pd_lower > phdr->pd_upper ||
        phdr->pd_upper > phdr->pd_special ||
        phdr->pd_special > BLCKSZ)
        ereport(PANIC,
                (errcode(ERRCODE_DATA_CORRUPTED),
                 errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
                        phdr->pd_lower, phdr->pd_upper, phdr->pd_special)));
 
    /*
     * Select offsetNumber to place the new item at
     */
    limit = OffsetNumberNext(PageGetMaxOffsetNumber(page));
 
    /* was offsetNumber passed in? */
    if (OffsetNumberIsValid(offsetNumber))
    {
        /* yes, check it */
        if ((flags & PAI_OVERWRITE) != 0)
        {
            if (offsetNumber < limit)
            {
                itemId = PageGetItemId(page, offsetNumber);
                if (ItemIdIsUsed(itemId) || ItemIdHasStorage(itemId))
                {
                    elog(WARNING, "will not overwrite a used ItemId");
                    return InvalidOffsetNumber;
                }
            }
        }
        else
        {
            if (offsetNumber < limit)
                needshuffle = true; /* need to move existing linp's */
        }
    }
    else
    {
        /* offsetNumber was not passed in, so find a free slot */
        /* if no free slot, we'll put it at limit (1st open slot) */
        if (PageHasFreeLinePointers(page))
        {
            /*
             * Scan line pointer array to locate a "recyclable" (unused)
             * ItemId.
             *
             * Always use earlier items first.  PageTruncateLinePointerArray
             * can only truncate unused items when they appear as a contiguous
             * group at the end of the line pointer array.
             */
            for (offsetNumber = FirstOffsetNumber;
                 offsetNumber < limit;  /* limit is maxoff+1 */
                 offsetNumber++)
            {
                itemId = PageGetItemId(page, offsetNumber);
 
                /*
                 * We check for no storage as well, just to be paranoid;
                 * unused items should never have storage.  Assert() that the
                 * invariant is respected too.
                 */
                Assert(ItemIdIsUsed(itemId) || !ItemIdHasStorage(itemId));
 
                if (!ItemIdIsUsed(itemId) && !ItemIdHasStorage(itemId))
                    break;
            }
            if (offsetNumber >= limit)
            {
                /* the hint is wrong, so reset it */
                PageClearHasFreeLinePointers(page);
            }
        }
        else
        {
            /* don't bother searching if hint says there's no free slot */
            offsetNumber = limit;
        }
    }
 
    /* Reject placing items beyond the first unused line pointer */
    if (offsetNumber > limit)
    {
        elog(WARNING, "specified item offset is too large");
        return InvalidOffsetNumber;
    }
 
    /* Reject placing items beyond heap boundary, if heap */
    if ((flags & PAI_IS_HEAP) != 0 && offsetNumber > MaxHeapTuplesPerPage)
    {
        elog(WARNING, "can't put more than MaxHeapTuplesPerPage items in a heap page");
        return InvalidOffsetNumber;
    }
 
    /*
     * Compute new lower and upper pointers for page, see if it'll fit.
     *
     * Note: do arithmetic as signed ints, to avoid mistakes if, say,
     * alignedSize > pd_upper.
     */
    if (offsetNumber == limit || needshuffle)
        lower = phdr->pd_lower + sizeof(ItemIdData);
    else
        lower = phdr->pd_lower;
 
    alignedSize = MAXALIGN(size);
 
    upper = (int) phdr->pd_upper - (int) alignedSize;
 
    if (lower > upper)
        return InvalidOffsetNumber;
 
    /*
     * OK to insert the item.  First, shuffle the existing pointers if needed.
     */
    itemId = PageGetItemId(page, offsetNumber);
 
    if (needshuffle)
        memmove(itemId + 1, itemId,
                (limit - offsetNumber) * sizeof(ItemIdData));
 
    /* set the line pointer */
    ItemIdSetNormal(itemId, upper, size);
 
    /*
     * Items normally contain no uninitialized bytes.  Core bufpage consumers
     * conform, but this is not a necessary coding rule; a new index AM could
     * opt to depart from it.  However, data type input functions and other
     * C-language functions that synthesize datums should initialize all
     * bytes; datumIsEqual() relies on this.  Testing here, along with the
     * similar check in printtup(), helps to catch such mistakes.
     *
     * Values of the "name" type retrieved via index-only scans may contain
     * uninitialized bytes; see comment in btrescan().  Valgrind will report
     * this as an error, but it is safe to ignore.
     */
    VALGRIND_CHECK_MEM_IS_DEFINED(item, size);
 
    /* copy the item's data onto the page */
    memcpy((char *) page + upper, item, size);
 
    /* adjust page header */
    phdr->pd_lower = (LocationIndex) lower;
    phdr->pd_upper = (LocationIndex) upper;
 
    return offsetNumber;
}

References Assert(), elog, ereport, errcode(), ERRCODE_DATA_CORRUPTED, errmsg(), FirstOffsetNumber, InvalidOffsetNumber, ItemIdHasStorage, ItemIdIsUsed, ItemIdSetNormal, lower(), MAXALIGN, MaxHeapTuplesPerPage, OffsetNumberIsValid, OffsetNumberNext, PageClearHasFreeLinePointers(), PageGetItemId(), PageGetMaxOffsetNumber(), PageHasFreeLinePointers(), PAI_IS_HEAP, PAI_OVERWRITE, PANIC, PageHeaderData::pd_lower, PageHeaderData::pd_special, PageHeaderData::pd_upper, SizeOfPageHeaderData, upper(), VALGRIND_CHECK_MEM_IS_DEFINED, and WARNING.

PageGetExactFreeSpace()

Size PageGetExactFreeSpace

(

const PageData *

page

)

Definition at line 947 of file bufpage.c.

{
    const PageHeaderData *phdr = (const PageHeaderData *) page;
    int         space;
 
    /*
     * Use signed arithmetic here so that we behave sensibly if pd_lower >
     * pd_upper.
     */
    space = (int) phdr->pd_upper - (int) phdr->pd_lower;
 
    if (space < 0)
        return 0;
 
    return (Size) space;
}

References PageHeaderData::pd_lower, and PageHeaderData::pd_upper.

Referenced by _bt_bottomupdel_pass(), _bt_dedup_pass(), _bt_findsplitloc(), allocNewBuffer(), brin_can_do_samepage_update(), doPickSplit(), GetHashPageStats(), ginHeapTupleFastInsert(), pgstat_heap(), pgstat_index_page(), pgstatindex_impl(), spgAddNodeAction(), SpGistGetBuffer(), SpGistPageAddNewItem(), SpGistSetLastUsedPage(), statapprox_heap(), and writeListPage().

PageGetFreeSpace()

Size PageGetFreeSpace

(

const PageData *

page

)

Definition at line 896 of file bufpage.c.

{
    const PageHeaderData *phdr = (const PageHeaderData *) page;
    int         space;
 
    /*
     * Use signed arithmetic here so that we behave sensibly if pd_lower >
     * pd_upper.
     */
    space = (int) phdr->pd_upper - (int) phdr->pd_lower;
 
    if (space < (int) sizeof(ItemIdData))
        return 0;
    space -= sizeof(ItemIdData);
 
    return (Size) space;
}

References PageHeaderData::pd_lower, and PageHeaderData::pd_upper.

Referenced by _bt_buildadd(), _bt_delete_or_dedup_one_page(), _bt_findinsertloc(), _bt_insertonpg(), _bt_search_insert(), _hash_doinsert(), br_page_get_freespace(), entryIsEnoughSpace(), GetBTPageStatistics(), GetHashPageStatistics(), gist_indexsortbuild_levelstate_add(), gistnospace(), heap_xlog_visible(), PageGetHeapFreeSpace(), and terminate_brin_buildstate().

PageGetFreeSpaceForMultipleTuples()

Size PageGetFreeSpaceForMultipleTuples	(	const PageData *	page,
		int	ntups
	)

Definition at line 923 of file bufpage.c.

{
    const PageHeaderData *phdr = (const PageHeaderData *) page;
    int         space;
 
    /*
     * Use signed arithmetic here so that we behave sensibly if pd_lower >
     * pd_upper.
     */
    space = (int) phdr->pd_upper - (int) phdr->pd_lower;
 
    if (space < (int) (ntups * sizeof(ItemIdData)))
        return 0;
    space -= ntups * sizeof(ItemIdData);
 
    return (Size) space;
}

References PageHeaderData::pd_lower, and PageHeaderData::pd_upper.

Referenced by _hash_splitbucket(), and _hash_squeezebucket().

PageGetHeapFreeSpace()

Size PageGetHeapFreeSpace

(

const PageData *

page

)

Definition at line 980 of file bufpage.c.

{
    Size        space;
 
    space = PageGetFreeSpace(page);
    if (space > 0)
    {
        OffsetNumber offnum,
                    nline;
 
        /*
         * Are there already MaxHeapTuplesPerPage line pointers in the page?
         */
        nline = PageGetMaxOffsetNumber(page);
        if (nline >= MaxHeapTuplesPerPage)
        {
            if (PageHasFreeLinePointers(page))
            {
                /*
                 * Since this is just a hint, we must confirm that there is
                 * indeed a free line pointer
                 */
                for (offnum = FirstOffsetNumber; offnum <= nline; offnum = OffsetNumberNext(offnum))
                {
                    ItemId      lp = PageGetItemId(unconstify(PageData *, page), offnum);
 
                    if (!ItemIdIsUsed(lp))
                        break;
                }
 
                if (offnum > nline)
                {
                    /*
                     * The hint is wrong, but we can't clear it here since we
                     * don't have the ability to mark the page dirty.
                     */
                    space = 0;
                }
            }
            else
            {
                /*
                 * Although the hint might be wrong, PageAddItem will believe
                 * it anyway, so we must believe it too.
                 */
                space = 0;
            }
        }
    }
    return space;
}

References FirstOffsetNumber, ItemIdIsUsed, MaxHeapTuplesPerPage, OffsetNumberNext, PageGetFreeSpace(), PageGetItemId(), PageGetMaxOffsetNumber(), PageHasFreeLinePointers(), and unconstify.

Referenced by heap_multi_insert(), heap_page_prune_opt(), heap_update(), heap_xlog_insert(), heap_xlog_multi_insert(), heap_xlog_prune_freeze(), heap_xlog_update(), lazy_scan_heap(), lazy_scan_new_or_empty(), lazy_vacuum_heap_rel(), raw_heap_insert(), and RelationGetBufferForTuple().

PageGetTempPage()

Page PageGetTempPage

(

const PageData *

page

)

Definition at line 354 of file bufpage.c.

{
    Size        pageSize;
    Page        temp;
 
    pageSize = PageGetPageSize(page);
    temp = (Page) palloc(pageSize);
 
    return temp;
}

References PageGetPageSize(), and palloc().

Referenced by _bt_split(), dataSplitPageInternal(), and ginPlaceToPage().

PageGetTempPageCopy()

Page PageGetTempPageCopy

(

const PageData *

page

)

Definition at line 371 of file bufpage.c.

{
    Size        pageSize;
    Page        temp;
 
    pageSize = PageGetPageSize(page);
    temp = (Page) palloc(pageSize);
 
    memcpy(temp, page, pageSize);
 
    return temp;
}

References PageGetPageSize(), and palloc().

Referenced by entrySplitPage(), and ginVacuumEntryPage().

PageGetTempPageCopySpecial()

Page PageGetTempPageCopySpecial

(

const PageData *

page

)

Definition at line 391 of file bufpage.c.

{
    Size        pageSize;
    Page        temp;
 
    pageSize = PageGetPageSize(page);
    temp = (Page) palloc(pageSize);
 
    PageInit(temp, pageSize, PageGetSpecialSize(page));
    memcpy(PageGetSpecialPointer(temp),
           PageGetSpecialPointer(page),
           PageGetSpecialSize(page));
 
    return temp;
}

References PageGetPageSize(), PageGetSpecialPointer, PageGetSpecialSize(), PageInit(), and palloc().

Referenced by _bt_dedup_pass(), btree_xlog_dedup(), btree_xlog_split(), and gistplacetopage().

PageIndexMultiDelete()

void PageIndexMultiDelete	(	Page	page,
		OffsetNumber *	itemnos,
		int	nitems
	)

Definition at line 1150 of file bufpage.c.

{
    PageHeader  phdr = (PageHeader) page;
    Offset      pd_lower = phdr->pd_lower;
    Offset      pd_upper = phdr->pd_upper;
    Offset      pd_special = phdr->pd_special;
    Offset      last_offset;
    itemIdCompactData itemidbase[MaxIndexTuplesPerPage];
    ItemIdData  newitemids[MaxIndexTuplesPerPage];
    itemIdCompact itemidptr;
    ItemId      lp;
    int         nline,
                nused;
    Size        totallen;
    Size        size;
    unsigned    offset;
    int         nextitm;
    OffsetNumber offnum;
    bool        presorted = true;   /* For now */
 
    Assert(nitems <= MaxIndexTuplesPerPage);
 
    /*
     * If there aren't very many items to delete, then retail
     * PageIndexTupleDelete is the best way.  Delete the items in reverse
     * order so we don't have to think about adjusting item numbers for
     * previous deletions.
     *
     * TODO: tune the magic number here
     */
    if (nitems <= 2)
    {
        while (--nitems >= 0)
            PageIndexTupleDelete(page, itemnos[nitems]);
        return;
    }
 
    /*
     * As with PageRepairFragmentation, paranoia seems justified.
     */
    if (pd_lower < SizeOfPageHeaderData ||
        pd_lower > pd_upper ||
        pd_upper > pd_special ||
        pd_special > BLCKSZ ||
        pd_special != MAXALIGN(pd_special))
        ereport(ERROR,
                (errcode(ERRCODE_DATA_CORRUPTED),
                 errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
                        pd_lower, pd_upper, pd_special)));
 
    /*
     * Scan the line pointer array and build a list of just the ones we are
     * going to keep.  Notice we do not modify the page yet, since we are
     * still validity-checking.
     */
    nline = PageGetMaxOffsetNumber(page);
    itemidptr = itemidbase;
    totallen = 0;
    nused = 0;
    nextitm = 0;
    last_offset = pd_special;
    for (offnum = FirstOffsetNumber; offnum <= nline; offnum = OffsetNumberNext(offnum))
    {
        lp = PageGetItemId(page, offnum);
        Assert(ItemIdHasStorage(lp));
        size = ItemIdGetLength(lp);
        offset = ItemIdGetOffset(lp);
        if (offset < pd_upper ||
            (offset + size) > pd_special ||
            offset != MAXALIGN(offset))
            ereport(ERROR,
                    (errcode(ERRCODE_DATA_CORRUPTED),
                     errmsg("corrupted line pointer: offset = %u, size = %u",
                            offset, (unsigned int) size)));
 
        if (nextitm < nitems && offnum == itemnos[nextitm])
        {
            /* skip item to be deleted */
            nextitm++;
        }
        else
        {
            itemidptr->offsetindex = nused; /* where it will go */
            itemidptr->itemoff = offset;
 
            if (last_offset > itemidptr->itemoff)
                last_offset = itemidptr->itemoff;
            else
                presorted = false;
 
            itemidptr->alignedlen = MAXALIGN(size);
            totallen += itemidptr->alignedlen;
            newitemids[nused] = *lp;
            itemidptr++;
            nused++;
        }
    }
 
    /* this will catch invalid or out-of-order itemnos[] */
    if (nextitm != nitems)
        elog(ERROR, "incorrect index offsets supplied");
 
    if (totallen > (Size) (pd_special - pd_lower))
        ereport(ERROR,
                (errcode(ERRCODE_DATA_CORRUPTED),
                 errmsg("corrupted item lengths: total %u, available space %u",
                        (unsigned int) totallen, pd_special - pd_lower)));
 
    /*
     * Looks good. Overwrite the line pointers with the copy, from which we've
     * removed all the unused items.
     */
    memcpy(phdr->pd_linp, newitemids, nused * sizeof(ItemIdData));
    phdr->pd_lower = SizeOfPageHeaderData + nused * sizeof(ItemIdData);
 
    /* and compactify the tuple data */
    if (nused > 0)
        compactify_tuples(itemidbase, nused, page, presorted);
    else
        phdr->pd_upper = pd_special;
}

References itemIdCompactData::alignedlen, Assert(), compactify_tuples(), elog, ereport, errcode(), ERRCODE_DATA_CORRUPTED, errmsg(), ERROR, FirstOffsetNumber, ItemIdGetLength, ItemIdGetOffset, ItemIdHasStorage, itemIdCompactData::itemoff, MAXALIGN, MaxIndexTuplesPerPage, nitems, itemIdCompactData::offsetindex, OffsetNumberNext, PageGetItemId(), PageGetMaxOffsetNumber(), PageIndexTupleDelete(), PageHeaderData::pd_linp, PageHeaderData::pd_lower, PageHeaderData::pd_special, PageHeaderData::pd_upper, and SizeOfPageHeaderData.

Referenced by _bt_delitems_delete(), _bt_delitems_vacuum(), _hash_squeezebucket(), _hash_vacuum_one_page(), btree_xlog_delete(), btree_xlog_vacuum(), gistprunepage(), gistRedoDeleteRecord(), gistRedoPageUpdateRecord(), gistvacuumpage(), hash_xlog_delete(), hash_xlog_move_page_contents(), hash_xlog_vacuum_one_page(), hashbucketcleanup(), spgPageIndexMultiDelete(), spgRedoVacuumRedirect(), spgRedoVacuumRoot(), vacuumLeafRoot(), and vacuumRedirectAndPlaceholder().

PageIndexTupleDelete()

void PageIndexTupleDelete	(	Page	page,
		OffsetNumber	offnum
	)

Definition at line 1041 of file bufpage.c.

{
    PageHeader  phdr = (PageHeader) page;
    char       *addr;
    ItemId      tup;
    Size        size;
    unsigned    offset;
    int         nbytes;
    int         offidx;
    int         nline;
 
    /*
     * As with PageRepairFragmentation, paranoia seems justified.
     */
    if (phdr->pd_lower < SizeOfPageHeaderData ||
        phdr->pd_lower > phdr->pd_upper ||
        phdr->pd_upper > phdr->pd_special ||
        phdr->pd_special > BLCKSZ ||
        phdr->pd_special != MAXALIGN(phdr->pd_special))
        ereport(ERROR,
                (errcode(ERRCODE_DATA_CORRUPTED),
                 errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
                        phdr->pd_lower, phdr->pd_upper, phdr->pd_special)));
 
    nline = PageGetMaxOffsetNumber(page);
    if ((int) offnum <= 0 || (int) offnum > nline)
        elog(ERROR, "invalid index offnum: %u", offnum);
 
    /* change offset number to offset index */
    offidx = offnum - 1;
 
    tup = PageGetItemId(page, offnum);
    Assert(ItemIdHasStorage(tup));
    size = ItemIdGetLength(tup);
    offset = ItemIdGetOffset(tup);
 
    if (offset < phdr->pd_upper || (offset + size) > phdr->pd_special ||
        offset != MAXALIGN(offset))
        ereport(ERROR,
                (errcode(ERRCODE_DATA_CORRUPTED),
                 errmsg("corrupted line pointer: offset = %u, size = %u",
                        offset, (unsigned int) size)));
 
    /* Amount of space to actually be deleted */
    size = MAXALIGN(size);
 
    /*
     * First, we want to get rid of the pd_linp entry for the index tuple. We
     * copy all subsequent linp's back one slot in the array. We don't use
     * PageGetItemId, because we are manipulating the _array_, not individual
     * linp's.
     */
    nbytes = phdr->pd_lower -
        ((char *) &phdr->pd_linp[offidx + 1] - (char *) phdr);
 
    if (nbytes > 0)
        memmove(&(phdr->pd_linp[offidx]),
                &(phdr->pd_linp[offidx + 1]),
                nbytes);
 
    /*
     * Now move everything between the old upper bound (beginning of tuple
     * space) and the beginning of the deleted tuple forward, so that space in
     * the middle of the page is left free.  If we've just deleted the tuple
     * at the beginning of tuple space, then there's no need to do the copy.
     */
 
    /* beginning of tuple space */
    addr = (char *) page + phdr->pd_upper;
 
    if (offset > phdr->pd_upper)
        memmove(addr + size, addr, offset - phdr->pd_upper);
 
    /* adjust free space boundary pointers */
    phdr->pd_upper += size;
    phdr->pd_lower -= sizeof(ItemIdData);
 
    /*
     * Finally, we need to adjust the linp entries that remain.
     *
     * Anything that used to be before the deleted tuple's data was moved
     * forward by the size of the deleted tuple.
     */
    if (!PageIsEmpty(page))
    {
        int         i;
 
        nline--;                /* there's one less than when we started */
        for (i = 1; i <= nline; i++)
        {
            ItemId      ii = PageGetItemId(page, i);
 
            Assert(ItemIdHasStorage(ii));
            if (ItemIdGetOffset(ii) <= offset)
                ii->lp_off += size;
        }
    }
}

References Assert(), elog, ereport, errcode(), ERRCODE_DATA_CORRUPTED, errmsg(), ERROR, i, if(), ItemIdGetLength, ItemIdGetOffset, ItemIdHasStorage, ItemIdData::lp_off, MAXALIGN, PageGetItemId(), PageGetMaxOffsetNumber(), PageIsEmpty(), PageHeaderData::pd_linp, PageHeaderData::pd_lower, PageHeaderData::pd_special, PageHeaderData::pd_upper, and SizeOfPageHeaderData.

Referenced by _bt_mark_page_halfdead(), addLeafTuple(), addOrReplaceTuple(), btree_xlog_mark_page_halfdead(), entryPreparePage(), ginRedoInsertEntry(), ginVacuumEntryPage(), gistdeletepage(), gistplacetopage(), gistRedoPageDelete(), PageIndexMultiDelete(), spgAddNodeAction(), SpGistPageAddNewItem(), spgRedoAddLeaf(), spgRedoAddNode(), spgRedoSplitTuple(), and spgSplitNodeAction().

PageIndexTupleDeleteNoCompact()

void PageIndexTupleDeleteNoCompact	(	Page	page,
		OffsetNumber	offnum
	)

Definition at line 1284 of file bufpage.c.

{
    PageHeader  phdr = (PageHeader) page;
    char       *addr;
    ItemId      tup;
    Size        size;
    unsigned    offset;
    int         nline;
 
    /*
     * As with PageRepairFragmentation, paranoia seems justified.
     */
    if (phdr->pd_lower < SizeOfPageHeaderData ||
        phdr->pd_lower > phdr->pd_upper ||
        phdr->pd_upper > phdr->pd_special ||
        phdr->pd_special > BLCKSZ ||
        phdr->pd_special != MAXALIGN(phdr->pd_special))
        ereport(ERROR,
                (errcode(ERRCODE_DATA_CORRUPTED),
                 errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
                        phdr->pd_lower, phdr->pd_upper, phdr->pd_special)));
 
    nline = PageGetMaxOffsetNumber(page);
    if ((int) offnum <= 0 || (int) offnum > nline)
        elog(ERROR, "invalid index offnum: %u", offnum);
 
    tup = PageGetItemId(page, offnum);
    Assert(ItemIdHasStorage(tup));
    size = ItemIdGetLength(tup);
    offset = ItemIdGetOffset(tup);
 
    if (offset < phdr->pd_upper || (offset + size) > phdr->pd_special ||
        offset != MAXALIGN(offset))
        ereport(ERROR,
                (errcode(ERRCODE_DATA_CORRUPTED),
                 errmsg("corrupted line pointer: offset = %u, size = %u",
                        offset, (unsigned int) size)));
 
    /* Amount of space to actually be deleted */
    size = MAXALIGN(size);
 
    /*
     * Either set the line pointer to "unused", or zap it if it's the last
     * one.  (Note: it's possible that the next-to-last one(s) are already
     * unused, but we do not trouble to try to compact them out if so.)
     */
    if ((int) offnum < nline)
        ItemIdSetUnused(tup);
    else
    {
        phdr->pd_lower -= sizeof(ItemIdData);
        nline--;                /* there's one less than when we started */
    }
 
    /*
     * Now move everything between the old upper bound (beginning of tuple
     * space) and the beginning of the deleted tuple forward, so that space in
     * the middle of the page is left free.  If we've just deleted the tuple
     * at the beginning of tuple space, then there's no need to do the copy.
     */
 
    /* beginning of tuple space */
    addr = (char *) page + phdr->pd_upper;
 
    if (offset > phdr->pd_upper)
        memmove(addr + size, addr, offset - phdr->pd_upper);
 
    /* adjust free space boundary pointer */
    phdr->pd_upper += size;
 
    /*
     * Finally, we need to adjust the linp entries that remain.
     *
     * Anything that used to be before the deleted tuple's data was moved
     * forward by the size of the deleted tuple.
     */
    if (!PageIsEmpty(page))
    {
        int         i;
 
        for (i = 1; i <= nline; i++)
        {
            ItemId      ii = PageGetItemId(page, i);
 
            if (ItemIdHasStorage(ii) && ItemIdGetOffset(ii) <= offset)
                ii->lp_off += size;
        }
    }
}

References Assert(), elog, ereport, errcode(), ERRCODE_DATA_CORRUPTED, errmsg(), ERROR, i, if(), ItemIdGetLength, ItemIdGetOffset, ItemIdHasStorage, ItemIdSetUnused, ItemIdData::lp_off, MAXALIGN, PageGetItemId(), PageGetMaxOffsetNumber(), PageIsEmpty(), PageHeaderData::pd_lower, PageHeaderData::pd_special, PageHeaderData::pd_upper, and SizeOfPageHeaderData.

Referenced by brin_doupdate(), brin_xlog_desummarize_page(), brin_xlog_update(), and brinRevmapDesummarizeRange().

PageIndexTupleOverwrite()

bool PageIndexTupleOverwrite	(	Page	page,
		OffsetNumber	offnum,
		Item	newtup,
		Size	newsize
	)

Definition at line 1394 of file bufpage.c.

{
    PageHeader  phdr = (PageHeader) page;
    ItemId      tupid;
    int         oldsize;
    unsigned    offset;
    Size        alignednewsize;
    int         size_diff;
    int         itemcount;
 
    /*
     * As with PageRepairFragmentation, paranoia seems justified.
     */
    if (phdr->pd_lower < SizeOfPageHeaderData ||
        phdr->pd_lower > phdr->pd_upper ||
        phdr->pd_upper > phdr->pd_special ||
        phdr->pd_special > BLCKSZ ||
        phdr->pd_special != MAXALIGN(phdr->pd_special))
        ereport(ERROR,
                (errcode(ERRCODE_DATA_CORRUPTED),
                 errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
                        phdr->pd_lower, phdr->pd_upper, phdr->pd_special)));
 
    itemcount = PageGetMaxOffsetNumber(page);
    if ((int) offnum <= 0 || (int) offnum > itemcount)
        elog(ERROR, "invalid index offnum: %u", offnum);
 
    tupid = PageGetItemId(page, offnum);
    Assert(ItemIdHasStorage(tupid));
    oldsize = ItemIdGetLength(tupid);
    offset = ItemIdGetOffset(tupid);
 
    if (offset < phdr->pd_upper || (offset + oldsize) > phdr->pd_special ||
        offset != MAXALIGN(offset))
        ereport(ERROR,
                (errcode(ERRCODE_DATA_CORRUPTED),
                 errmsg("corrupted line pointer: offset = %u, size = %u",
                        offset, (unsigned int) oldsize)));
 
    /*
     * Determine actual change in space requirement, check for page overflow.
     */
    oldsize = MAXALIGN(oldsize);
    alignednewsize = MAXALIGN(newsize);
    if (alignednewsize > oldsize + (phdr->pd_upper - phdr->pd_lower))
        return false;
 
    /*
     * Relocate existing data and update line pointers, unless the new tuple
     * is the same size as the old (after alignment), in which case there's
     * nothing to do.  Notice that what we have to relocate is data before the
     * target tuple, not data after, so it's convenient to express size_diff
     * as the amount by which the tuple's size is decreasing, making it the
     * delta to add to pd_upper and affected line pointers.
     */
    size_diff = oldsize - (int) alignednewsize;
    if (size_diff != 0)
    {
        char       *addr = (char *) page + phdr->pd_upper;
        int         i;
 
        /* relocate all tuple data before the target tuple */
        memmove(addr + size_diff, addr, offset - phdr->pd_upper);
 
        /* adjust free space boundary pointer */
        phdr->pd_upper += size_diff;
 
        /* adjust affected line pointers too */
        for (i = FirstOffsetNumber; i <= itemcount; i++)
        {
            ItemId      ii = PageGetItemId(page, i);
 
            /* Allow items without storage; currently only BRIN needs that */
            if (ItemIdHasStorage(ii) && ItemIdGetOffset(ii) <= offset)
                ii->lp_off += size_diff;
        }
    }
 
    /* Update the item's tuple length without changing its lp_flags field */
    tupid->lp_off = offset + size_diff;
    tupid->lp_len = newsize;
 
    /* Copy new tuple data onto page */
    memcpy(PageGetItem(page, tupid), newtup, newsize);
 
    return true;
}

References Assert(), elog, ereport, errcode(), ERRCODE_DATA_CORRUPTED, errmsg(), ERROR, FirstOffsetNumber, i, ItemIdGetLength, ItemIdGetOffset, ItemIdHasStorage, ItemIdData::lp_len, ItemIdData::lp_off, MAXALIGN, PageGetItem(), PageGetItemId(), PageGetMaxOffsetNumber(), PageHeaderData::pd_lower, PageHeaderData::pd_special, PageHeaderData::pd_upper, and SizeOfPageHeaderData.

Referenced by _bt_buildadd(), _bt_delitems_delete(), _bt_delitems_vacuum(), _bt_mark_page_halfdead(), brin_doupdate(), brin_xlog_samepage_update(), btree_xlog_updates(), gistplacetopage(), and gistRedoPageUpdateRecord().

PageInit()

void PageInit	(	Page	page,
		Size	pageSize,
		Size	specialSize
	)

Definition at line 42 of file bufpage.c.

{
    PageHeader  p = (PageHeader) page;
 
    specialSize = MAXALIGN(specialSize);
 
    Assert(pageSize == BLCKSZ);
    Assert(pageSize > specialSize + SizeOfPageHeaderData);
 
    /* Make sure all fields of page are zero, as well as unused space */
    MemSet(p, 0, pageSize);
 
    p->pd_flags = 0;
    p->pd_lower = SizeOfPageHeaderData;
    p->pd_upper = pageSize - specialSize;
    p->pd_special = pageSize - specialSize;
    PageSetPageSizeAndVersion(page, pageSize, PG_PAGE_LAYOUT_VERSION);
    /* p->pd_prune_xid = InvalidTransactionId;      done by above MemSet */
}

References Assert(), MAXALIGN, MemSet, PageSetPageSizeAndVersion(), PageHeaderData::pd_flags, PageHeaderData::pd_lower, PageHeaderData::pd_special, PageHeaderData::pd_upper, PG_PAGE_LAYOUT_VERSION, and SizeOfPageHeaderData.

Referenced by _bt_pageinit(), _hash_pageinit(), BloomInitPage(), brin_page_init(), fill_seq_fork_with_data(), fsm_readbuf(), GinInitPage(), gistinitpage(), heap_xlog_insert(), heap_xlog_multi_insert(), heap_xlog_update(), heap_xlog_visible(), PageGetTempPageCopySpecial(), raw_heap_insert(), RelationAddBlocks(), RelationGetBufferForTuple(), seq_redo(), SpGistInitPage(), vm_readbuf(), and XLogRecordPageWithFreeSpace().

PageIsVerifiedExtended()

bool PageIsVerifiedExtended	(	PageData *	page,
		BlockNumber	blkno,
		int	flags
	)

Definition at line 88 of file bufpage.c.

{
    const PageHeaderData *p = (const PageHeaderData *) page;
    size_t     *pagebytes;
    bool        checksum_failure = false;
    bool        header_sane = false;
    uint16      checksum = 0;
 
    /*
     * Don't verify page data unless the page passes basic non-zero test
     */
    if (!PageIsNew(page))
    {
        if (DataChecksumsEnabled())
        {
            checksum = pg_checksum_page(page, blkno);
 
            if (checksum != p->pd_checksum)
                checksum_failure = true;
        }
 
        /*
         * The following checks don't prove the header is correct, only that
         * it looks sane enough to allow into the buffer pool. Later usage of
         * the block can still reveal problems, which is why we offer the
         * checksum option.
         */
        if ((p->pd_flags & ~PD_VALID_FLAG_BITS) == 0 &&
            p->pd_lower <= p->pd_upper &&
            p->pd_upper <= p->pd_special &&
            p->pd_special <= BLCKSZ &&
            p->pd_special == MAXALIGN(p->pd_special))
            header_sane = true;
 
        if (header_sane && !checksum_failure)
            return true;
    }
 
    /* Check all-zeroes case */
    pagebytes = (size_t *) page;
 
    if (pg_memory_is_all_zeros(pagebytes, BLCKSZ))
        return true;
 
    /*
     * Throw a WARNING if the checksum fails, but only after we've checked for
     * the all-zeroes case.
     */
    if (checksum_failure)
    {
        if ((flags & PIV_LOG_WARNING) != 0)
            ereport(WARNING,
                    (errcode(ERRCODE_DATA_CORRUPTED),
                     errmsg("page verification failed, calculated checksum %u but expected %u",
                            checksum, p->pd_checksum)));
 
        if ((flags & PIV_REPORT_STAT) != 0)
            pgstat_report_checksum_failure();
 
        if (header_sane && ignore_checksum_failure)
            return true;
    }
 
    return false;
}

References checksum_failure, DataChecksumsEnabled(), ereport, errcode(), ERRCODE_DATA_CORRUPTED, errmsg(), ignore_checksum_failure, MAXALIGN, PageIsNew(), PageHeaderData::pd_checksum, PageHeaderData::pd_flags, PageHeaderData::pd_lower, PageHeaderData::pd_special, PageHeaderData::pd_upper, PD_VALID_FLAG_BITS, pg_checksum_page(), pg_memory_is_all_zeros(), pgstat_report_checksum_failure(), PIV_LOG_WARNING, PIV_REPORT_STAT, and WARNING.

Referenced by RelationCopyStorage(), and WaitReadBuffers().

PageRepairFragmentation()

void PageRepairFragmentation

(

Page

page

)

Definition at line 688 of file bufpage.c.

{
    Offset      pd_lower = ((PageHeader) page)->pd_lower;
    Offset      pd_upper = ((PageHeader) page)->pd_upper;
    Offset      pd_special = ((PageHeader) page)->pd_special;
    Offset      last_offset;
    itemIdCompactData itemidbase[MaxHeapTuplesPerPage];
    itemIdCompact itemidptr;
    ItemId      lp;
    int         nline,
                nstorage,
                nunused;
    OffsetNumber finalusedlp = InvalidOffsetNumber;
    int         i;
    Size        totallen;
    bool        presorted = true;   /* For now */
 
    /*
     * It's worth the trouble to be more paranoid here than in most places,
     * because we are about to reshuffle data in (what is usually) a shared
     * disk buffer.  If we aren't careful then corrupted pointers, lengths,
     * etc could cause us to clobber adjacent disk buffers, spreading the data
     * loss further.  So, check everything.
     */
    if (pd_lower < SizeOfPageHeaderData ||
        pd_lower > pd_upper ||
        pd_upper > pd_special ||
        pd_special > BLCKSZ ||
        pd_special != MAXALIGN(pd_special))
        ereport(ERROR,
                (errcode(ERRCODE_DATA_CORRUPTED),
                 errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
                        pd_lower, pd_upper, pd_special)));
 
    /*
     * Run through the line pointer array and collect data about live items.
     */
    nline = PageGetMaxOffsetNumber(page);
    itemidptr = itemidbase;
    nunused = totallen = 0;
    last_offset = pd_special;
    for (i = FirstOffsetNumber; i <= nline; i++)
    {
        lp = PageGetItemId(page, i);
        if (ItemIdIsUsed(lp))
        {
            if (ItemIdHasStorage(lp))
            {
                itemidptr->offsetindex = i - 1;
                itemidptr->itemoff = ItemIdGetOffset(lp);
 
                if (last_offset > itemidptr->itemoff)
                    last_offset = itemidptr->itemoff;
                else
                    presorted = false;
 
                if (unlikely(itemidptr->itemoff < (int) pd_upper ||
                             itemidptr->itemoff >= (int) pd_special))
                    ereport(ERROR,
                            (errcode(ERRCODE_DATA_CORRUPTED),
                             errmsg("corrupted line pointer: %u",
                                    itemidptr->itemoff)));
                itemidptr->alignedlen = MAXALIGN(ItemIdGetLength(lp));
                totallen += itemidptr->alignedlen;
                itemidptr++;
            }
 
            finalusedlp = i;    /* Could be the final non-LP_UNUSED item */
        }
        else
        {
            /* Unused entries should have lp_len = 0, but make sure */
            Assert(!ItemIdHasStorage(lp));
            ItemIdSetUnused(lp);
            nunused++;
        }
    }
 
    nstorage = itemidptr - itemidbase;
    if (nstorage == 0)
    {
        /* Page is completely empty, so just reset it quickly */
        ((PageHeader) page)->pd_upper = pd_special;
    }
    else
    {
        /* Need to compact the page the hard way */
        if (totallen > (Size) (pd_special - pd_lower))
            ereport(ERROR,
                    (errcode(ERRCODE_DATA_CORRUPTED),
                     errmsg("corrupted item lengths: total %u, available space %u",
                            (unsigned int) totallen, pd_special - pd_lower)));
 
        compactify_tuples(itemidbase, nstorage, page, presorted);
    }
 
    if (finalusedlp != nline)
    {
        /* The last line pointer is not the last used line pointer */
        int         nunusedend = nline - finalusedlp;
 
        Assert(nunused >= nunusedend && nunusedend > 0);
 
        /* remove trailing unused line pointers from the count */
        nunused -= nunusedend;
        /* truncate the line pointer array */
        ((PageHeader) page)->pd_lower -= (sizeof(ItemIdData) * nunusedend);
    }
 
    /* Set hint bit for PageAddItemExtended */
    if (nunused > 0)
        PageSetHasFreeLinePointers(page);
    else
        PageClearHasFreeLinePointers(page);
}

References itemIdCompactData::alignedlen, Assert(), compactify_tuples(), ereport, errcode(), ERRCODE_DATA_CORRUPTED, errmsg(), ERROR, FirstOffsetNumber, i, InvalidOffsetNumber, ItemIdGetLength, ItemIdGetOffset, ItemIdHasStorage, ItemIdIsUsed, ItemIdSetUnused, itemIdCompactData::itemoff, MAXALIGN, MaxHeapTuplesPerPage, itemIdCompactData::offsetindex, PageClearHasFreeLinePointers(), PageGetItemId(), PageGetMaxOffsetNumber(), PageSetHasFreeLinePointers(), SizeOfPageHeaderData, and unlikely.

Referenced by heap_page_prune_execute().

PageRestoreTempPage()

void PageRestoreTempPage	(	Page	tempPage,
		Page	oldPage
	)

Definition at line 413 of file bufpage.c.

{
    Size        pageSize;
 
    pageSize = PageGetPageSize(tempPage);
    memcpy(oldPage, tempPage, pageSize);
 
    pfree(tempPage);
}

References PageGetPageSize(), and pfree().

Referenced by _bt_dedup_pass(), _bt_split(), btree_xlog_dedup(), btree_xlog_split(), createPostingTree(), ginbulkdelete(), and gistplacetopage().

PageSetChecksumCopy()

char * PageSetChecksumCopy	(	Page	page,
		BlockNumber	blkno
	)

Definition at line 1499 of file bufpage.c.

{
    static char *pageCopy = NULL;
 
    /* If we don't need a checksum, just return the passed-in data */
    if (PageIsNew(page) || !DataChecksumsEnabled())
        return page;
 
    /*
     * We allocate the copy space once and use it over on each subsequent
     * call.  The point of palloc'ing here, rather than having a static char
     * array, is first to ensure adequate alignment for the checksumming code
     * and second to avoid wasting space in processes that never call this.
     */
    if (pageCopy == NULL)
        pageCopy = MemoryContextAllocAligned(TopMemoryContext,
                                             BLCKSZ,
                                             PG_IO_ALIGN_SIZE,
                                             0);
 
    memcpy(pageCopy, page, BLCKSZ);
    ((PageHeader) pageCopy)->pd_checksum = pg_checksum_page(pageCopy, blkno);
    return pageCopy;
}

References DataChecksumsEnabled(), MemoryContextAllocAligned(), PageIsNew(), pg_checksum_page(), PG_IO_ALIGN_SIZE, and TopMemoryContext.

Referenced by FlushBuffer().

PageSetChecksumInplace()

void PageSetChecksumInplace	(	Page	page,
		BlockNumber	blkno
	)

Definition at line 1531 of file bufpage.c.

{
    /* If we don't need a checksum, just return */
    if (PageIsNew(page) || !DataChecksumsEnabled())
        return;
 
    ((PageHeader) page)->pd_checksum = pg_checksum_page(page, blkno);
}

References DataChecksumsEnabled(), PageIsNew(), and pg_checksum_page().

Referenced by _hash_alloc_buckets(), FlushLocalBuffer(), and smgr_bulk_flush().

PageTruncateLinePointerArray()

void PageTruncateLinePointerArray

(

Page

page

)

Definition at line 824 of file bufpage.c.

{
    PageHeader  phdr = (PageHeader) page;
    bool        countdone = false,
                sethint = false;
    int         nunusedend = 0;
 
    /* Scan line pointer array back-to-front */
    for (int i = PageGetMaxOffsetNumber(page); i >= FirstOffsetNumber; i--)
    {
        ItemId      lp = PageGetItemId(page, i);
 
        if (!countdone && i > FirstOffsetNumber)
        {
            /*
             * Still determining which line pointers from the end of the array
             * will be truncated away.  Either count another line pointer as
             * safe to truncate, or notice that it's not safe to truncate
             * additional line pointers (stop counting line pointers).
             */
            if (!ItemIdIsUsed(lp))
                nunusedend++;
            else
                countdone = true;
        }
        else
        {
            /*
             * Once we've stopped counting we still need to figure out if
             * there are any remaining LP_UNUSED line pointers somewhere more
             * towards the front of the array.
             */
            if (!ItemIdIsUsed(lp))
            {
                /*
                 * This is an unused line pointer that we won't be truncating
                 * away -- so there is at least one.  Set hint on page.
                 */
                sethint = true;
                break;
            }
        }
    }
 
    if (nunusedend > 0)
    {
        phdr->pd_lower -= sizeof(ItemIdData) * nunusedend;
 
#ifdef CLOBBER_FREED_MEMORY
        memset((char *) page + phdr->pd_lower, 0x7F,
               sizeof(ItemIdData) * nunusedend);
#endif
    }
    else
        Assert(sethint);
 
    /* Set hint bit for PageAddItemExtended */
    if (sethint)
        PageSetHasFreeLinePointers(page);
    else
        PageClearHasFreeLinePointers(page);
}

References Assert(), FirstOffsetNumber, i, ItemIdIsUsed, PageClearHasFreeLinePointers(), PageGetItemId(), PageGetMaxOffsetNumber(), PageSetHasFreeLinePointers(), and PageHeaderData::pd_lower.

Referenced by heap_page_prune_execute(), and lazy_vacuum_heap_page().

Variable Documentation

ignore_checksum_failure

bool ignore_checksum_failure = false

Definition at line 27 of file bufpage.c.

Referenced by PageIsVerifiedExtended().