diff options
Diffstat (limited to 'src/backend/storage/page/bufpage.c')
| -rw-r--r-- | src/backend/storage/page/bufpage.c | 112 |
1 files changed, 94 insertions, 18 deletions
diff --git a/src/backend/storage/page/bufpage.c b/src/backend/storage/page/bufpage.c index 3ce2f04bd8e..b382e4d0240 100644 --- a/src/backend/storage/page/bufpage.c +++ b/src/backend/storage/page/bufpage.c @@ -8,12 +8,13 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.73 2007/09/12 22:10:26 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.74 2007/09/20 17:56:31 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" +#include "access/htup.h" #include "storage/bufpage.h" @@ -108,6 +109,9 @@ PageHeaderIsValid(PageHeader page) * If offsetNumber is not valid, then assign one by finding the first * one that is both unused and deallocated. * + * If is_heap is true, we enforce that there can't be more than + * MaxHeapTuplesPerPage line pointers on the page. + * * !!! EREPORT(ERROR) IS DISALLOWED HERE !!! */ OffsetNumber @@ -115,7 +119,8 @@ PageAddItem(Page page, Item item, Size size, OffsetNumber offsetNumber, - bool overwrite) + bool overwrite, + bool is_heap) { PageHeader phdr = (PageHeader) page; Size alignedSize; @@ -200,6 +205,12 @@ PageAddItem(Page page, return InvalidOffsetNumber; } + if (is_heap && 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. * @@ -315,11 +326,10 @@ itemoffcompare(const void *itemidp1, const void *itemidp2) * * This routine is usable for heap pages only, but see PageIndexMultiDelete. * - * Returns number of unused line pointers on page. If "unused" is not NULL - * then the unused[] array is filled with indexes of unused line pointers. + * As a side effect, the page's PD_HAS_FREE_LINES hint bit is updated. */ -int -PageRepairFragmentation(Page page, OffsetNumber *unused) +void +PageRepairFragmentation(Page page) { Offset pd_lower = ((PageHeader) page)->pd_lower; Offset pd_upper = ((PageHeader) page)->pd_upper; @@ -329,7 +339,7 @@ PageRepairFragmentation(Page page, OffsetNumber *unused) ItemId lp; int nline, nstorage, - nused; + nunused; int i; Size totallen; Offset upper; @@ -352,13 +362,12 @@ PageRepairFragmentation(Page page, OffsetNumber *unused) pd_lower, pd_upper, pd_special))); nline = PageGetMaxOffsetNumber(page); - nused = nstorage = 0; - for (i = 0; i < nline; i++) + nunused = nstorage = 0; + for (i = FirstOffsetNumber; i <= nline; i++) { - lp = PageGetItemId(page, i + 1); + lp = PageGetItemId(page, i); if (ItemIdIsUsed(lp)) { - nused++; if (ItemIdHasStorage(lp)) nstorage++; } @@ -366,9 +375,7 @@ PageRepairFragmentation(Page page, OffsetNumber *unused) { /* Unused entries should have lp_len = 0, but make sure */ ItemIdSetUnused(lp); - /* Report to caller if asked for */ - if (unused) - unused[i - nused] = (OffsetNumber) i; + nunused++; } } @@ -431,18 +438,19 @@ PageRepairFragmentation(Page page, OffsetNumber *unused) } /* Set hint bit for PageAddItem */ - if (nused < nline) + if (nunused > 0) PageSetHasFreeLinePointers(page); else PageClearHasFreeLinePointers(page); - - return (nline - nused); } /* * PageGetFreeSpace * Returns the size of the free (allocatable) space on a page, * reduced by the space needed for a new line pointer. + * + * Note: this should usually only be used on index pages. Use + * PageGetHeapFreeSpace on heap pages. */ Size PageGetFreeSpace(Page page) @@ -465,7 +473,8 @@ PageGetFreeSpace(Page page) /* * PageGetExactFreeSpace - * Returns the size of the free (allocatable) space on a page. + * Returns the size of the free (allocatable) space on a page, + * without any consideration for adding/removing line pointers. */ Size PageGetExactFreeSpace(Page page) @@ -484,6 +493,73 @@ PageGetExactFreeSpace(Page page) /* + * PageGetHeapFreeSpace + * Returns the size of the free (allocatable) space on a page, + * reduced by the space needed for a new line pointer. + * + * The difference between this and PageGetFreeSpace is that this will return + * zero if there are already MaxHeapTuplesPerPage line pointers in the page + * and none are free. We use this to enforce that no more than + * MaxHeapTuplesPerPage line pointers are created on a heap page. (Although + * no more tuples than that could fit anyway, in the presence of redirected + * or dead line pointers it'd be possible to have too many line pointers. + * To avoid breaking code that assumes MaxHeapTuplesPerPage is a hard limit + * on the number of line pointers, we make this extra check.) + */ +Size +PageGetHeapFreeSpace(Page page) +{ + 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((PageHeader) page)) + { + /* + * Since this is just a hint, we must confirm that there is + * indeed a free line pointer + */ + for (offnum = FirstOffsetNumber; offnum <= nline; offnum++) + { + ItemId lp = PageGetItemId(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; +} + + +/* * PageIndexTupleDelete * * This routine does the work of removing a tuple from an index page. |