Page access

There already was a macro PageGetItemId; this is now used in (almost)
all places, where pd_linp is accessed. Also introduce new macros
SizeOfPageHeaderData and BTMaxItemSize.
This is just source code cosmetic, no behaviour changed.
All 81 tests passed.

Servus
Manfred

diff -ru ../base/src/backend/access/heap/heapam.c src/backend/access/heap/heapam.c
--- ../base/src/backend/access/heap/heapam.c 2002-06-17 22:35:32.000000000 +0200
+++ src/backend/access/heap/heapam.c 2002-06-19 16:57:07.000000000 +0200
@@ -2067,7 +2067,7 @@

while ((char *) unused < unend)
{
- lp = ((PageHeader) page)->pd_linp + *unused;
+ lp = PageGetItemId(page, *unused + 1);
lp->lp_flags &= ~LP_USED;
unused++;
}
diff -ru ../base/src/backend/access/nbtree/nbtinsert.c src/backend/access/nbtree/nbtinsert.c
--- ../base/src/backend/access/nbtree/nbtinsert.c 2002-05-27 16:29:37.000000000 +0200
+++ src/backend/access/nbtree/nbtinsert.c 2002-06-20 12:19:57.000000000 +0200
@@ -383,10 +383,9 @@
* to 1/3 the per-page available space. Note that at this point,
* itemsz doesn't include the ItemId.
*/
- if (itemsz > (PageGetPageSize(page) - sizeof(PageHeaderData) - MAXALIGN(sizeof(BTPageOpaqueData))) / 3 - sizeof(ItemIdData))
+ if (itemsz > BTMaxItemSize(page))
elog(ERROR, "btree: index item size %lu exceeds maximum %lu",
- (unsigned long) itemsz,
- (PageGetPageSize(page) - sizeof(PageHeaderData) - MAXALIGN(sizeof(BTPageOpaqueData))) / 3 - sizeof(ItemIdData));
+ (unsigned long) itemsz, BTMaxItemSize(page));

/*
* Determine exactly where new item will go.
@@ -1020,9 +1019,8 @@

/* Total free space available on a btree page, after fixed overhead */
leftspace = rightspace =
- PageGetPageSize(page) - sizeof(PageHeaderData) -
- MAXALIGN(sizeof(BTPageOpaqueData))
- +sizeof(ItemIdData);
+ PageGetPageSize(page) - SizeOfPageHeaderData -
+ MAXALIGN(sizeof(BTPageOpaqueData));

/*
* Finding the best possible split would require checking all the
diff -ru ../base/src/backend/access/nbtree/nbtsort.c src/backend/access/nbtree/nbtsort.c
--- ../base/src/backend/access/nbtree/nbtsort.c 2001-11-11 01:51:13.000000000 +0100
+++ src/backend/access/nbtree/nbtsort.c 2002-06-20 12:27:41.000000000 +0200
@@ -346,10 +346,9 @@
* oversize items being inserted into an already-existing index. But
* during creation of an index, we don't go through there.
*/
- if (btisz > (PageGetPageSize(npage) - sizeof(PageHeaderData) - MAXALIGN(sizeof(BTPageOpaqueData))) / 3 - sizeof(ItemIdData))
+ if (btisz > BTMaxItemSize(npage))
elog(ERROR, "btree: index item size %lu exceeds maximum %ld",
- (unsigned long) btisz,
- (PageGetPageSize(npage) - sizeof(PageHeaderData) - MAXALIGN(sizeof(BTPageOpaqueData))) / 3 - sizeof(ItemIdData));
+ (unsigned long) btisz, BTMaxItemSize(npage));

if (pgspc < btisz || pgspc < state->btps_full)
{
diff -ru ../base/src/backend/storage/page/bufpage.c src/backend/storage/page/bufpage.c
--- ../base/src/backend/storage/page/bufpage.c 2002-03-06 08:10:07.000000000 +0100
+++ src/backend/storage/page/bufpage.c 2002-06-20 09:40:12.000000000 +0200
@@ -37,13 +37,12 @@
specialSize = MAXALIGN(specialSize);

Assert(pageSize == BLCKSZ);
- Assert(pageSize >
- specialSize + sizeof(PageHeaderData) - sizeof(ItemIdData));
+ Assert(pageSize > specialSize + SizeOfPageHeaderData);

/* Make sure all fields of page are zero, as well as unused space */
MemSet(p, 0, pageSize);

- p->pd_lower = sizeof(PageHeaderData) - sizeof(ItemIdData);
+ p->pd_lower = SizeOfPageHeaderData;
p->pd_upper = pageSize - specialSize;
p->pd_special = pageSize - specialSize;
PageSetPageSize(page, pageSize);
@@ -88,7 +87,7 @@
/*
* Be wary about corrupted page pointers
*/
- if (phdr->pd_lower < (sizeof(PageHeaderData) - sizeof(ItemIdData)) ||
+ if (phdr->pd_lower < SizeOfPageHeaderData ||
phdr->pd_lower > phdr->pd_upper ||
phdr->pd_upper > phdr->pd_special ||
phdr->pd_special > BLCKSZ)
@@ -112,7 +111,7 @@
}
if (offsetNumber < limit)
{
- itemId = &phdr->pd_linp[offsetNumber - 1];
+ itemId = PageGetItemId(phdr, offsetNumber);
if (((*itemId).lp_flags & LP_USED) ||
((*itemId).lp_len != 0))
{
@@ -136,7 +135,7 @@
/* look for "recyclable" (unused & deallocated) ItemId */
for (offsetNumber = 1; offsetNumber < limit; offsetNumber++)
{
- itemId = &phdr->pd_linp[offsetNumber - 1];
+ itemId = PageGetItemId(phdr, offsetNumber);
if ((((*itemId).lp_flags & LP_USED) == 0) &&
((*itemId).lp_len == 0))
break;
@@ -150,7 +149,7 @@
* alignedSize > pd_upper.
*/
if (offsetNumber > limit)
- lower = (char *) (&phdr->pd_linp[offsetNumber]) - (char *) page;
+ lower = (char *) PageGetItemId(phdr, offsetNumber + 1) - (char *) page;
else if (offsetNumber == limit || needshuffle)
lower = phdr->pd_lower + sizeof(ItemIdData);
else
@@ -175,13 +174,13 @@
ItemId fromitemId,
toitemId;

- fromitemId = &phdr->pd_linp[i - 1];
- toitemId = &phdr->pd_linp[i];
+ fromitemId = PageGetItemId(phdr, i);
+ toitemId = PageGetItemId(phdr, i + 1);
*toitemId = *fromitemId;
}
}

- itemId = &phdr->pd_linp[offsetNumber - 1];
+ itemId = PageGetItemId(phdr, offsetNumber);
(*itemId).lp_off = upper;
(*itemId).lp_len = size;
(*itemId).lp_flags = flags;
@@ -214,12 +213,12 @@
memcpy(temp, page, pageSize);

/* clear out the middle */
- size = (pageSize - sizeof(PageHeaderData)) + sizeof(ItemIdData);
+ size = pageSize - SizeOfPageHeaderData;
size -= MAXALIGN(specialSize);
- MemSet((char *) &(thdr->pd_linp[0]), 0, size);
+ MemSet(PageGetContents(thdr), 0, size);

/* set high, low water marks */
- thdr->pd_lower = sizeof(PageHeaderData) - sizeof(ItemIdData);
+ thdr->pd_lower = SizeOfPageHeaderData;
thdr->pd_upper = pageSize - MAXALIGN(specialSize);

return temp;
@@ -291,7 +290,7 @@
* pointers, lengths, etc could cause us to clobber adjacent disk
* buffers, spreading the data loss further. So, check everything.
*/
- if (pd_lower < (sizeof(PageHeaderData) - sizeof(ItemIdData)) ||
+ if (pd_lower < SizeOfPageHeaderData ||
pd_lower > pd_upper ||
pd_upper > pd_special ||
pd_special > BLCKSZ ||
@@ -303,7 +302,7 @@
nused = 0;
for (i = 0; i < nline; i++)
{
- lp = ((PageHeader) page)->pd_linp + i;
+ lp = PageGetItemId(page, i + 1);
if ((*lp).lp_flags & LP_DELETE) /* marked for deletion */
(*lp).lp_flags &= ~(LP_USED | LP_DELETE);
if ((*lp).lp_flags & LP_USED)
@@ -317,7 +316,7 @@
/* Page is completely empty, so just reset it quickly */
for (i = 0; i < nline; i++)
{
- lp = ((PageHeader) page)->pd_linp + i;
+ lp = PageGetItemId(page, i + 1);
(*lp).lp_len = 0; /* indicate unused & deallocated */
}
((PageHeader) page)->pd_upper = pd_special;
@@ -331,7 +330,7 @@
totallen = 0;
for (i = 0; i < nline; i++)
{
- lp = ((PageHeader) page)->pd_linp + i;
+ lp = PageGetItemId(page, i + 1);
if ((*lp).lp_flags & LP_USED)
{
itemidptr->offsetindex = i;
@@ -363,7 +362,7 @@

for (i = 0, itemidptr = itemidbase; i < nused; i++, itemidptr++)
{
- lp = ((PageHeader) page)->pd_linp + itemidptr->offsetindex;
+ lp = PageGetItemId(page, itemidptr->offsetindex + 1);
upper -= itemidptr->alignedlen;
memmove((char *) page + upper,
(char *) page + itemidptr->itemoff,
@@ -426,7 +425,7 @@
/*
* As with PageRepairFragmentation, paranoia seems justified.
*/
- if (phdr->pd_lower < (sizeof(PageHeaderData) - sizeof(ItemIdData)) ||
+ if (phdr->pd_lower < SizeOfPageHeaderData ||
phdr->pd_lower > phdr->pd_upper ||
phdr->pd_upper > phdr->pd_special ||
phdr->pd_special > BLCKSZ)
@@ -452,6 +451,8 @@
/*
* 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);
@@ -490,8 +491,8 @@
nline--; /* there's one less than when we started */
for (i = nline; --i >= 0; )
{
- if (phdr->pd_linp[i].lp_off <= offset)
- phdr->pd_linp[i].lp_off += size;
+ if (PageGetItemId(phdr, i + 1)->lp_off <= offset)
+ PageGetItemId(phdr, i + 1)->lp_off += size;
}
}
}
diff -ru ../base/src/include/access/nbtree.h src/include/access/nbtree.h
--- ../base/src/include/access/nbtree.h 2002-05-27 16:29:39.000000000 +0200
+++ src/include/access/nbtree.h 2002-06-20 12:11:01.000000000 +0200
@@ -65,7 +65,7 @@
} BTMetaPageData;

#define BTPageGetMeta(p) \
- ((BTMetaPageData *) &((PageHeader) p)->pd_linp[0])
+ ((BTMetaPageData *) PageGetContents(p))

#define BTREE_METAPAGE 0 /* first page is meta */
#define BTREE_MAGIC 0x053162 /* magic number of btree pages */
@@ -77,6 +77,14 @@
#define BTREE_VERSION 1

/*
+ * We actually need to be able to fit three items on every page,
+ * so restrict any one item to 1/3 the per-page available space.
+ */
+#define BTMaxItemSize(page) \
+ ((PageGetPageSize(page) - \
+ sizeof(PageHeaderData) - \
+ MAXALIGN(sizeof(BTPageOpaqueData))) / 3 - sizeof(ItemIdData))
+/*
* BTScanOpaqueData is used to remember which buffers we're currently
* examining in the scan. We keep these buffers pinned (but not locked,
* see nbtree.c) and recorded in the opaque entry of the scan to avoid
diff -ru ../base/src/include/storage/bufpage.h src/include/storage/bufpage.h
--- ../base/src/include/storage/bufpage.h 2002-01-16 00:14:17.000000000 +0100
+++ src/include/storage/bufpage.h 2002-06-20 12:22:21.000000000 +0200
@@ -158,12 +158,16 @@
)

/*
+ * line pointer does not count as part of header
+ */
+#define SizeOfPageHeaderData (offsetof(PageHeaderData, pd_linp[0]))
+
+/*
* PageIsEmpty
* returns true iff no itemid has been allocated on the page
*/
#define PageIsEmpty(page) \
- (((PageHeader) (page))->pd_lower <= \
- (sizeof(PageHeaderData) - sizeof(ItemIdData)))
+ (((PageHeader) (page))->pd_lower <= SizeOfPageHeaderData)

/*
* PageIsNew
@@ -179,6 +183,13 @@
#define PageGetItemId(page, offsetNumber) \
((ItemId) (&((PageHeader) (page))->pd_linp[(offsetNumber) - 1]))

+/*
+ * PageGetContents
+ * To be used in case the page does not contain item pointers.
+ */
+#define PageGetContents(page) \
+ ((char *) (&((PageHeader) (page))->pd_linp[0]))
+
/* ----------------
* macros to access opaque space
* ----------------
@@ -290,8 +301,7 @@
* That way we get -1 or so, not a huge positive number...
*/
#define PageGetMaxOffsetNumber(page) \
- (((int) (((PageHeader) (page))->pd_lower - \
- (sizeof(PageHeaderData) - sizeof(ItemIdData)))) \
+ (((int) (((PageHeader) (page))->pd_lower - SizeOfPageHeaderData)) \
/ ((int) sizeof(ItemIdData)))

#define PageGetLSN(page) \