/*
* PageIndexMultiDelete
*
* This routine handles the case of deleting multiple tuples from an
* index page at once. It is considerably faster than a loop around
* PageIndexTupleDelete ... however, the caller *must* supply the array
* of item numbers to be deleted in item number order!
*/
void
PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
{
PageHeader phdr = (PageHeader) page;
Offset pd_lower = phdr->pd_lower;
Offset pd_upper = phdr->pd_upper;
Offset pd_special = phdr->pd_special;
itemIdSortData itemidbase[MaxIndexTuplesPerPage];
ItemIdData newitemids[MaxIndexTuplesPerPage];
itemIdSort itemidptr;
ItemId lp;
int nline,
nused;
Size totallen;
Size size;
unsigned offset;
int nextitm;
OffsetNumber offnum;
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 item 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;
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 item pointer: offset = %u, length = %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;
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 */
compactify_tuples(itemidbase, nused, page);
}
/*
* PageIndexTupleDeleteNoCompact
*
* Remove the specified tuple from an index page, but set its line pointer
* to "unused" instead of compacting it out, except that it can be removed
* if it's the last line pointer on the page.
*
* This is used for index AMs that require that existing TIDs of live tuples
* remain unchanged, and are willing to allow unused line pointers instead.
*/
void
PageIndexTupleDeleteNoCompact(Page page, OffsetNumber offnum)
{
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 item pointer: offset = %u, size = %u",
offset, (unsigned int) size)));
/* Amount of space to actually be deleted */
size = MAXALIGN(size);
/*
* Either set the item 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(phdr, i);
if (ItemIdHasStorage(ii) && ItemIdGetOffset(ii) <= offset)
ii->lp_off += size;
}
}
}
/*
* PageRepairFragmentation
*
* Frees fragmented space on a page.
* It doesn't remove unused line pointers! Please don't change this.
*
* This routine is usable for heap pages only, but see PageIndexMultiDelete.
*
* As a side effect, the page's PD_HAS_FREE_LINES hint bit is updated.
*/
void
PageRepairFragmentation(Page page)
{
Offset pd_lower = ((PageHeader) page)->pd_lower;
Offset pd_upper = ((PageHeader) page)->pd_upper;
Offset pd_special = ((PageHeader) page)->pd_special;
ItemId lp;
int nline,
nstorage,
nunused;
int i;
Size totallen;
/*
* 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)));
nline = PageGetMaxOffsetNumber(page);
nunused = nstorage = 0;
for (i = FirstOffsetNumber; i <= nline; i++)
{
lp = PageGetItemId(page, i);
if (ItemIdIsUsed(lp))
{
if (ItemIdHasStorage(lp))
nstorage++;
}
else
{
/* Unused entries should have lp_len = 0, but make sure */
ItemIdSetUnused(lp);
nunused++;
}
}
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 */
itemIdSortData itemidbase[MaxHeapTuplesPerPage];
itemIdSort itemidptr = itemidbase;
totallen = 0;
for (i = 0; i < nline; i++)
{
lp = PageGetItemId(page, i + 1);
if (ItemIdHasStorage(lp))
{
itemidptr->offsetindex = i;
itemidptr->itemoff = ItemIdGetOffset(lp);
if (itemidptr->itemoff < (int) pd_upper ||
itemidptr->itemoff >= (int) pd_special)
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg("corrupted item pointer: %u",
itemidptr->itemoff)));
itemidptr->alignedlen = MAXALIGN(ItemIdGetLength(lp));
totallen += itemidptr->alignedlen;
itemidptr++;
}
}
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);
}
/* Set hint bit for PageAddItem */
if (nunused > 0)
PageSetHasFreeLinePointers(page);
else
PageClearHasFreeLinePointers(page);
}
/*
* PageIndexTupleDelete
*
* This routine does the work of removing a tuple from an index page.
*
* Unlike heap pages, we compact out the line pointer for the removed tuple.
*/
void
PageIndexTupleDelete(Page page, OffsetNumber offnum)
{
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 item 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((char *) &(phdr->pd_linp[offidx]),
(char *) &(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(phdr, i);
Assert(ItemIdHasStorage(ii));
if (ItemIdGetOffset(ii) <= offset)
ii->lp_off += size;
}
}
}
/*
* PageIndexTupleOverwrite
*
* Replace a specified tuple on an index page.
*
* The new tuple is placed exactly where the old one had been, shifting
* other tuples' data up or down as needed to keep the page compacted.
* This is better than deleting and reinserting the tuple, because it
* avoids any data shifting when the tuple size doesn't change; and
* even when it does, we avoid moving the item pointers around.
* Conceivably this could also be of use to an index AM that cares about
* the physical order of tuples as well as their ItemId order.
*
* If there's insufficient space for the new tuple, return false. Other
* errors represent data-corruption problems, so we just elog.
*/
bool
PageIndexTupleOverwrite(Page page, OffsetNumber offnum,
Item newtup, Size newsize)
{
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 item 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(phdr, 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 (other fields shouldn't change) */
ItemIdSetNormal(tupid, offset + size_diff, newsize);
/* Copy new tuple data onto page */
memcpy(PageGetItem(page, tupid), newtup, newsize);
return true;
}
Datum
heap_page_items(PG_FUNCTION_ARGS)
{
bytea *raw_page = PG_GETARG_BYTEA_P(0);
heap_page_items_state *inter_call_data = NULL;
FuncCallContext *fctx;
int raw_page_size;
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
(errmsg("must be superuser to use raw page functions"))));
raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
if (SRF_IS_FIRSTCALL())
{
TupleDesc tupdesc;
MemoryContext mctx;
if (raw_page_size < SizeOfPageHeaderData)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("input page too small (%d bytes)", raw_page_size)));
fctx = SRF_FIRSTCALL_INIT();
mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
inter_call_data = palloc(sizeof(heap_page_items_state));
/* Build a tuple descriptor for our result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
inter_call_data->tupd = tupdesc;
inter_call_data->offset = FirstOffsetNumber;
inter_call_data->page = VARDATA(raw_page);
fctx->max_calls = PageGetMaxOffsetNumber(inter_call_data->page);
fctx->user_fctx = inter_call_data;
MemoryContextSwitchTo(mctx);
}
fctx = SRF_PERCALL_SETUP();
inter_call_data = fctx->user_fctx;
if (fctx->call_cntr < fctx->max_calls)
{
Page page = inter_call_data->page;
HeapTuple resultTuple;
Datum result;
ItemId id;
Datum values[13];
bool nulls[13];
uint16 lp_offset;
uint16 lp_flags;
uint16 lp_len;
memset(nulls, 0, sizeof(nulls));
/* Extract information from the line pointer */
id = PageGetItemId(page, inter_call_data->offset);
lp_offset = ItemIdGetOffset(id);
lp_flags = ItemIdGetFlags(id);
lp_len = ItemIdGetLength(id);
values[0] = UInt16GetDatum(inter_call_data->offset);
values[1] = UInt16GetDatum(lp_offset);
values[2] = UInt16GetDatum(lp_flags);
values[3] = UInt16GetDatum(lp_len);
/*
* We do just enough validity checking to make sure we don't reference
* data outside the page passed to us. The page could be corrupt in
* many other ways, but at least we won't crash.
*/
if (ItemIdHasStorage(id) &&
lp_len >= sizeof(HeapTupleHeader) &&
lp_offset == MAXALIGN(lp_offset) &&
lp_offset + lp_len <= raw_page_size)
{
HeapTupleHeader tuphdr;
int bits_len;
/* Extract information from the tuple header */
tuphdr = (HeapTupleHeader) PageGetItem(page, id);
values[4] = UInt32GetDatum(HeapTupleHeaderGetXmin(tuphdr));
values[5] = UInt32GetDatum(HeapTupleHeaderGetRawXmax(tuphdr));
values[6] = UInt32GetDatum(HeapTupleHeaderGetRawCommandId(tuphdr)); /* shared with xvac */
values[7] = PointerGetDatum(&tuphdr->t_ctid);
values[8] = UInt32GetDatum(tuphdr->t_infomask2);
values[9] = UInt32GetDatum(tuphdr->t_infomask);
values[10] = UInt8GetDatum(tuphdr->t_hoff);
/*
* We already checked that the item as is completely within the
* raw page passed to us, with the length given in the line
* pointer.. Let's check that t_hoff doesn't point over lp_len,
* before using it to access t_bits and oid.
*/
if (tuphdr->t_hoff >= sizeof(HeapTupleHeader) &&
tuphdr->t_hoff <= lp_len)
{
if (tuphdr->t_infomask & HEAP_HASNULL)
{
bits_len = tuphdr->t_hoff -
(((char *) tuphdr->t_bits) -((char *) tuphdr));
values[11] = CStringGetTextDatum(
bits_to_text(tuphdr->t_bits, bits_len * 8));
}
else
nulls[11] = true;
if (tuphdr->t_infomask & HEAP_HASOID)
values[12] = HeapTupleHeaderGetOid(tuphdr);
else
nulls[12] = true;
}
else
{
nulls[11] = true;
nulls[12] = true;
}
}
else
{
/*
* The line pointer is not used, or it's invalid. Set the rest of
* the fields to NULL
*/
int i;
for (i = 4; i <= 12; i++)
nulls[i] = true;
}
/* Build and return the result tuple. */
resultTuple = heap_form_tuple(inter_call_data->tupd, values, nulls);
result = HeapTupleGetDatum(resultTuple);
inter_call_data->offset++;
SRF_RETURN_NEXT(fctx, result);
}
else
SRF_RETURN_DONE(fctx);
}
/*
* PageIndexDeleteNoCompact
* Delete the given items for an index page, and defragment the resulting
* free space, but do not compact the item pointers array.
*
* itemnos is the array of tuples to delete; nitems is its size. maxIdxTuples
* is the maximum number of tuples that can exist in a page.
*
* Unused items at the end of the array are removed.
*
* This is used for index AMs that require that existing TIDs of live tuples
* remain unchanged.
*/
void
PageIndexDeleteNoCompact(Page page, OffsetNumber *itemnos, int nitems)
{
PageHeader phdr = (PageHeader) page;
LocationIndex pd_lower = phdr->pd_lower;
LocationIndex pd_upper = phdr->pd_upper;
LocationIndex pd_special = phdr->pd_special;
int nline;
bool empty;
OffsetNumber offnum;
int nextitm;
/*
* 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 existing item pointer array and mark as unused those that are
* in our kill-list; make sure any non-interesting ones are marked unused
* as well.
*/
nline = PageGetMaxOffsetNumber(page);
empty = true;
nextitm = 0;
for (offnum = FirstOffsetNumber; offnum <= nline; offnum = OffsetNumberNext(offnum))
{
ItemId lp;
ItemLength itemlen;
ItemOffset offset;
lp = PageGetItemId(page, offnum);
itemlen = ItemIdGetLength(lp);
offset = ItemIdGetOffset(lp);
if (ItemIdIsUsed(lp))
{
if (offset < pd_upper ||
(offset + itemlen) > pd_special ||
offset != MAXALIGN(offset))
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg("corrupted item pointer: offset = %u, length = %u",
offset, (unsigned int) itemlen)));
if (nextitm < nitems && offnum == itemnos[nextitm])
{
/* this one is on our list to delete, so mark it unused */
ItemIdSetUnused(lp);
nextitm++;
}
else if (ItemIdHasStorage(lp))
{
/* This one's live -- must do the compaction dance */
empty = false;
}
else
{
/* get rid of this one too */
ItemIdSetUnused(lp);
}
}
}
/* this will catch invalid or out-of-order itemnos[] */
if (nextitm != nitems)
elog(ERROR, "incorrect index offsets supplied");
if (empty)
{
/* Page is completely empty, so just reset it quickly */
phdr->pd_lower = SizeOfPageHeaderData;
phdr->pd_upper = pd_special;
}
else
{
/* There are live items: need to compact the page the hard way */
itemIdSortData itemidbase[MaxOffsetNumber];
itemIdSort itemidptr;
int i;
Size totallen;
/*
* Scan the page taking note of each item that we need to preserve.
* This includes both live items (those that contain data) and
* interspersed unused ones. It's critical to preserve these unused
* items, because otherwise the offset numbers for later live items
* would change, which is not acceptable. Unused items might get used
* again later; that is fine.
*/
itemidptr = itemidbase;
totallen = 0;
PageClearHasFreeLinePointers(page);
for (i = 0; i < nline; i++)
{
ItemId lp;
itemidptr->offsetindex = i;
lp = PageGetItemId(page, i + 1);
if (ItemIdHasStorage(lp))
{
itemidptr->itemoff = ItemIdGetOffset(lp);
itemidptr->alignedlen = MAXALIGN(ItemIdGetLength(lp));
totallen += itemidptr->alignedlen;
itemidptr++;
}
else
{
PageSetHasFreeLinePointers(page);
ItemIdSetUnused(lp);
}
}
nline = itemidptr - itemidbase;
/* By here, there are exactly nline elements in itemidbase array */
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)));
/*
* Defragment the data areas of each tuple, being careful to preserve
* each item's position in the linp array.
*/
compactify_tuples(itemidbase, nline, page);
}
}
/*
* PageIndexMultiDelete
*
* This routine handles the case of deleting multiple tuples from an
* index page at once. It is considerably faster than a loop around
* PageIndexTupleDelete ... however, the caller *must* supply the array
* of item numbers to be deleted in item number order!
*/
void
PageIndexMultiDelete(Page page, OffsetNumber *itemnos, int nitems)
{
PageHeader phdr = (PageHeader) page;
Offset pd_lower = phdr->pd_lower;
Offset pd_upper = phdr->pd_upper;
Offset pd_special = phdr->pd_special;
itemIdSort itemidbase,
itemidptr;
ItemId lp;
int nline,
nused;
int i;
Size totallen;
Offset upper;
Size size;
unsigned offset;
int nextitm;
OffsetNumber offnum;
/*
* 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 item 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);
itemidbase = (itemIdSort) palloc(sizeof(itemIdSortData) * nline);
itemidptr = itemidbase;
totallen = 0;
nused = 0;
nextitm = 0;
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 item 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;
itemidptr->olditemid = *lp;
itemidptr->alignedlen = MAXALIGN(size);
totallen += itemidptr->alignedlen;
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)));
/* sort itemIdSortData array into decreasing itemoff order */
qsort((char *) itemidbase, nused, sizeof(itemIdSortData),
itemoffcompare);
/* compactify page and install new itemids */
upper = pd_special;
for (i = 0, itemidptr = itemidbase; i < nused; i++, itemidptr++)
{
lp = PageGetItemId(page, itemidptr->offsetindex + 1);
upper -= itemidptr->alignedlen;
memmove((char *) page + upper,
(char *) page + itemidptr->itemoff,
itemidptr->alignedlen);
*lp = itemidptr->olditemid;
lp->lp_off = upper;
}
phdr->pd_lower = SizeOfPageHeaderData + nused * sizeof(ItemIdData);
phdr->pd_upper = upper;
pfree(itemidbase);
}
/*
* PageRepairFragmentation
*
* Frees fragmented space on a page.
* It doesn't remove unused line pointers! Please don't change this.
*
* 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.
*/
int
PageRepairFragmentation(Page page, OffsetNumber *unused)
{
Offset pd_lower = ((PageHeader) page)->pd_lower;
Offset pd_upper = ((PageHeader) page)->pd_upper;
Offset pd_special = ((PageHeader) page)->pd_special;
itemIdSort itemidbase,
itemidptr;
ItemId lp;
int nline,
nused;
int i;
Size totallen;
Offset upper;
/*
* 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),
errSendAlert(true)));
nline = PageGetMaxOffsetNumber(page);
nused = 0;
for (i = 0; i < nline; i++)
{
lp = PageGetItemId(page, i + 1);
if (ItemIdDeleted(lp)) /* marked for deletion */
lp->lp_flags &= ~(LP_USED | LP_DELETE);
if (ItemIdIsUsed(lp))
nused++;
else if (unused)
unused[i - nused] = (OffsetNumber) i;
}
if (nused == 0)
{
/* Page is completely empty, so just reset it quickly */
for (i = 0; i < nline; i++)
{
lp = PageGetItemId(page, i + 1);
lp->lp_len = 0; /* indicate unused & deallocated */
}
((PageHeader) page)->pd_upper = pd_special;
}
else
{ /* nused != 0 */
/* Need to compact the page the hard way */
itemidbase = (itemIdSort) palloc(sizeof(itemIdSortData) * nused);
itemidptr = itemidbase;
totallen = 0;
for (i = 0; i < nline; i++)
{
lp = PageGetItemId(page, i + 1);
if (ItemIdIsUsed(lp))
{
itemidptr->offsetindex = i;
itemidptr->itemoff = ItemIdGetOffset(lp);
if (itemidptr->itemoff < (int) pd_upper ||
itemidptr->itemoff >= (int) pd_special)
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg("corrupted item pointer: %u",
itemidptr->itemoff),
errSendAlert(true)));
itemidptr->alignedlen = MAXALIGN(ItemIdGetLength(lp));
totallen += itemidptr->alignedlen;
itemidptr++;
}
else
{
lp->lp_len = 0; /* indicate unused & deallocated */
}
}
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),
errSendAlert(true)));
/* sort itemIdSortData array into decreasing itemoff order */
qsort((char *) itemidbase, nused, sizeof(itemIdSortData),
itemoffcompare);
/* compactify page */
upper = pd_special;
for (i = 0, itemidptr = itemidbase; i < nused; i++, itemidptr++)
{
lp = PageGetItemId(page, itemidptr->offsetindex + 1);
upper -= itemidptr->alignedlen;
memmove((char *) page + upper,
(char *) page + itemidptr->itemoff,
itemidptr->alignedlen);
lp->lp_off = upper;
}
((PageHeader) page)->pd_upper = upper;
pfree(itemidbase);
}
/* Set hint bit for PageAddItem */
if (nused < nline)
PageSetHasFreeLinePointers(page);
else
PageClearHasFreeLinePointers(page);
return (nline - nused);
}