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postgresql/src/backend/access/heap/heaptoast.c

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/*-------------------------------------------------------------------------
*
* heaptoast.c
* Heap-specific definitions for external and compressed storage
* of variable size attributes.
*
* Copyright (c) 2000-2024, PostgreSQL Global Development Group
*
*
* IDENTIFICATION
* src/backend/access/heap/heaptoast.c
*
*
* INTERFACE ROUTINES
* heap_toast_insert_or_update -
* Try to make a given tuple fit into one page by compressing
* or moving off attributes
*
* heap_toast_delete -
* Reclaim toast storage when a tuple is deleted
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/detoast.h"
#include "access/genam.h"
#include "access/heapam.h"
#include "access/heaptoast.h"
#include "access/toast_helper.h"
#include "access/toast_internals.h"
#include "utils/fmgroids.h"
/* ----------
* heap_toast_delete -
*
* Cascaded delete toast-entries on DELETE
* ----------
*/
void
heap_toast_delete(Relation rel, HeapTuple oldtup, bool is_speculative)
{
TupleDesc tupleDesc;
Datum toast_values[MaxHeapAttributeNumber];
bool toast_isnull[MaxHeapAttributeNumber];
/*
* We should only ever be called for tuples of plain relations or
* materialized views --- recursing on a toast rel is bad news.
*/
Assert(rel->rd_rel->relkind == RELKIND_RELATION ||
rel->rd_rel->relkind == RELKIND_MATVIEW);
/*
* Get the tuple descriptor and break down the tuple into fields.
*
* NOTE: it's debatable whether to use heap_deform_tuple() here or just
* heap_getattr() only the varlena columns. The latter could win if there
* are few varlena columns and many non-varlena ones. However,
* heap_deform_tuple costs only O(N) while the heap_getattr way would cost
* O(N^2) if there are many varlena columns, so it seems better to err on
* the side of linear cost. (We won't even be here unless there's at
* least one varlena column, by the way.)
*/
tupleDesc = rel->rd_att;
Assert(tupleDesc->natts <= MaxHeapAttributeNumber);
heap_deform_tuple(oldtup, tupleDesc, toast_values, toast_isnull);
/* Do the real work. */
toast_delete_external(rel, toast_values, toast_isnull, is_speculative);
}
/* ----------
* heap_toast_insert_or_update -
*
* Delete no-longer-used toast-entries and create new ones to
* make the new tuple fit on INSERT or UPDATE
*
* Inputs:
* newtup: the candidate new tuple to be inserted
* oldtup: the old row version for UPDATE, or NULL for INSERT
* options: options to be passed to heap_insert() for toast rows
* Result:
* either newtup if no toasting is needed, or a palloc'd modified tuple
* that is what should actually get stored
*
* NOTE: neither newtup nor oldtup will be modified. This is a change
* from the pre-8.1 API of this routine.
* ----------
*/
HeapTuple
heap_toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup,
int options)
{
HeapTuple result_tuple;
TupleDesc tupleDesc;
int numAttrs;
Size maxDataLen;
Size hoff;
bool toast_isnull[MaxHeapAttributeNumber];
bool toast_oldisnull[MaxHeapAttributeNumber];
Datum toast_values[MaxHeapAttributeNumber];
Datum toast_oldvalues[MaxHeapAttributeNumber];
ToastAttrInfo toast_attr[MaxHeapAttributeNumber];
ToastTupleContext ttc;
/*
* Ignore the INSERT_SPECULATIVE option. Speculative insertions/super
* deletions just normally insert/delete the toast values. It seems
* easiest to deal with that here, instead on, potentially, multiple
* callers.
*/
options &= ~HEAP_INSERT_SPECULATIVE;
/*
* We should only ever be called for tuples of plain relations or
* materialized views --- recursing on a toast rel is bad news.
*/
Assert(rel->rd_rel->relkind == RELKIND_RELATION ||
rel->rd_rel->relkind == RELKIND_MATVIEW);
/*
* Get the tuple descriptor and break down the tuple(s) into fields.
*/
tupleDesc = rel->rd_att;
numAttrs = tupleDesc->natts;
Assert(numAttrs <= MaxHeapAttributeNumber);
heap_deform_tuple(newtup, tupleDesc, toast_values, toast_isnull);
if (oldtup != NULL)
heap_deform_tuple(oldtup, tupleDesc, toast_oldvalues, toast_oldisnull);
/* ----------
* Prepare for toasting
* ----------
*/
ttc.ttc_rel = rel;
ttc.ttc_values = toast_values;
ttc.ttc_isnull = toast_isnull;
if (oldtup == NULL)
{
ttc.ttc_oldvalues = NULL;
ttc.ttc_oldisnull = NULL;
}
else
{
ttc.ttc_oldvalues = toast_oldvalues;
ttc.ttc_oldisnull = toast_oldisnull;
}
ttc.ttc_attr = toast_attr;
toast_tuple_init(&ttc);
/* ----------
* Compress and/or save external until data fits into target length
*
* 1: Inline compress attributes with attstorage EXTENDED, and store very
* large attributes with attstorage EXTENDED or EXTERNAL external
* immediately
* 2: Store attributes with attstorage EXTENDED or EXTERNAL external
* 3: Inline compress attributes with attstorage MAIN
* 4: Store attributes with attstorage MAIN external
* ----------
*/
/* compute header overhead --- this should match heap_form_tuple() */
hoff = SizeofHeapTupleHeader;
if ((ttc.ttc_flags & TOAST_HAS_NULLS) != 0)
hoff += BITMAPLEN(numAttrs);
hoff = MAXALIGN(hoff);
/* now convert to a limit on the tuple data size */
maxDataLen = RelationGetToastTupleTarget(rel, TOAST_TUPLE_TARGET) - hoff;
/*
* Look for attributes with attstorage EXTENDED to compress. Also find
* large attributes with attstorage EXTENDED or EXTERNAL, and store them
* external.
*/
while (heap_compute_data_size(tupleDesc,
toast_values, toast_isnull) > maxDataLen)
{
int biggest_attno;
biggest_attno = toast_tuple_find_biggest_attribute(&ttc, true, false);
if (biggest_attno < 0)
break;
/*
* Attempt to compress it inline, if it has attstorage EXTENDED
*/
if (TupleDescAttr(tupleDesc, biggest_attno)->attstorage == TYPSTORAGE_EXTENDED)
toast_tuple_try_compression(&ttc, biggest_attno);
else
{
/*
* has attstorage EXTERNAL, ignore on subsequent compression
* passes
*/
toast_attr[biggest_attno].tai_colflags |= TOASTCOL_INCOMPRESSIBLE;
}
/*
* If this value is by itself more than maxDataLen (after compression
* if any), push it out to the toast table immediately, if possible.
* This avoids uselessly compressing other fields in the common case
* where we have one long field and several short ones.
*
* XXX maybe the threshold should be less than maxDataLen?
*/
if (toast_attr[biggest_attno].tai_size > maxDataLen &&
rel->rd_rel->reltoastrelid != InvalidOid)
toast_tuple_externalize(&ttc, biggest_attno, options);
}
/*
* Second we look for attributes of attstorage EXTENDED or EXTERNAL that
* are still inline, and make them external. But skip this if there's no
* toast table to push them to.
*/
while (heap_compute_data_size(tupleDesc,
toast_values, toast_isnull) > maxDataLen &&
rel->rd_rel->reltoastrelid != InvalidOid)
{
int biggest_attno;
biggest_attno = toast_tuple_find_biggest_attribute(&ttc, false, false);
if (biggest_attno < 0)
break;
toast_tuple_externalize(&ttc, biggest_attno, options);
}
/*
* Round 3 - this time we take attributes with storage MAIN into
* compression
*/
while (heap_compute_data_size(tupleDesc,
toast_values, toast_isnull) > maxDataLen)
{
int biggest_attno;
biggest_attno = toast_tuple_find_biggest_attribute(&ttc, true, true);
if (biggest_attno < 0)
break;
toast_tuple_try_compression(&ttc, biggest_attno);
}
/*
* Finally we store attributes of type MAIN externally. At this point we
* increase the target tuple size, so that MAIN attributes aren't stored
* externally unless really necessary.
*/
maxDataLen = TOAST_TUPLE_TARGET_MAIN - hoff;
while (heap_compute_data_size(tupleDesc,
toast_values, toast_isnull) > maxDataLen &&
rel->rd_rel->reltoastrelid != InvalidOid)
{
int biggest_attno;
biggest_attno = toast_tuple_find_biggest_attribute(&ttc, false, true);
if (biggest_attno < 0)
break;
toast_tuple_externalize(&ttc, biggest_attno, options);
}
/*
* In the case we toasted any values, we need to build a new heap tuple
* with the changed values.
*/
if ((ttc.ttc_flags & TOAST_NEEDS_CHANGE) != 0)
{
HeapTupleHeader olddata = newtup->t_data;
HeapTupleHeader new_data;
int32 new_header_len;
int32 new_data_len;
int32 new_tuple_len;
/*
* Calculate the new size of the tuple.
*
* Note: we used to assume here that the old tuple's t_hoff must equal
* the new_header_len value, but that was incorrect. The old tuple
* might have a smaller-than-current natts, if there's been an ALTER
* TABLE ADD COLUMN since it was stored; and that would lead to a
* different conclusion about the size of the null bitmap, or even
* whether there needs to be one at all.
*/
new_header_len = SizeofHeapTupleHeader;
if ((ttc.ttc_flags & TOAST_HAS_NULLS) != 0)
new_header_len += BITMAPLEN(numAttrs);
new_header_len = MAXALIGN(new_header_len);
new_data_len = heap_compute_data_size(tupleDesc,
toast_values, toast_isnull);
new_tuple_len = new_header_len + new_data_len;
/*
* Allocate and zero the space needed, and fill HeapTupleData fields.
*/
result_tuple = (HeapTuple) palloc0(HEAPTUPLESIZE + new_tuple_len);
result_tuple->t_len = new_tuple_len;
result_tuple->t_self = newtup->t_self;
result_tuple->t_tableOid = newtup->t_tableOid;
new_data = (HeapTupleHeader) ((char *) result_tuple + HEAPTUPLESIZE);
result_tuple->t_data = new_data;
/*
* Copy the existing tuple header, but adjust natts and t_hoff.
*/
memcpy(new_data, olddata, SizeofHeapTupleHeader);
HeapTupleHeaderSetNatts(new_data, numAttrs);
new_data->t_hoff = new_header_len;
/* Copy over the data, and fill the null bitmap if needed */
heap_fill_tuple(tupleDesc,
toast_values,
toast_isnull,
(char *) new_data + new_header_len,
new_data_len,
&(new_data->t_infomask),
((ttc.ttc_flags & TOAST_HAS_NULLS) != 0) ?
new_data->t_bits : NULL);
}
else
result_tuple = newtup;
toast_tuple_cleanup(&ttc);
return result_tuple;
}
/* ----------
* toast_flatten_tuple -
*
* "Flatten" a tuple to contain no out-of-line toasted fields.
* (This does not eliminate compressed or short-header datums.)
*
* Note: we expect the caller already checked HeapTupleHasExternal(tup),
* so there is no need for a short-circuit path.
* ----------
*/
HeapTuple
toast_flatten_tuple(HeapTuple tup, TupleDesc tupleDesc)
{
HeapTuple new_tuple;
int numAttrs = tupleDesc->natts;
int i;
Datum toast_values[MaxTupleAttributeNumber];
bool toast_isnull[MaxTupleAttributeNumber];
bool toast_free[MaxTupleAttributeNumber];
/*
* Break down the tuple into fields.
*/
Assert(numAttrs <= MaxTupleAttributeNumber);
heap_deform_tuple(tup, tupleDesc, toast_values, toast_isnull);
memset(toast_free, 0, numAttrs * sizeof(bool));
for (i = 0; i < numAttrs; i++)
{
/*
* Look at non-null varlena attributes
*/
if (!toast_isnull[i] && TupleDescAttr(tupleDesc, i)->attlen == -1)
{
struct varlena *new_value;
new_value = (struct varlena *) DatumGetPointer(toast_values[i]);
if (VARATT_IS_EXTERNAL(new_value))
{
new_value = detoast_external_attr(new_value);
toast_values[i] = PointerGetDatum(new_value);
toast_free[i] = true;
}
}
}
/*
* Form the reconfigured tuple.
*/
new_tuple = heap_form_tuple(tupleDesc, toast_values, toast_isnull);
/*
* Be sure to copy the tuple's identity fields. We also make a point of
* copying visibility info, just in case anybody looks at those fields in
* a syscache entry.
*/
new_tuple->t_self = tup->t_self;
new_tuple->t_tableOid = tup->t_tableOid;
new_tuple->t_data->t_choice = tup->t_data->t_choice;
new_tuple->t_data->t_ctid = tup->t_data->t_ctid;
new_tuple->t_data->t_infomask &= ~HEAP_XACT_MASK;
new_tuple->t_data->t_infomask |=
tup->t_data->t_infomask & HEAP_XACT_MASK;
new_tuple->t_data->t_infomask2 &= ~HEAP2_XACT_MASK;
new_tuple->t_data->t_infomask2 |=
tup->t_data->t_infomask2 & HEAP2_XACT_MASK;
/*
* Free allocated temp values
*/
for (i = 0; i < numAttrs; i++)
if (toast_free[i])
pfree(DatumGetPointer(toast_values[i]));
return new_tuple;
}
/* ----------
* toast_flatten_tuple_to_datum -
*
* "Flatten" a tuple containing out-of-line toasted fields into a Datum.
* The result is always palloc'd in the current memory context.
*
* We have a general rule that Datums of container types (rows, arrays,
* ranges, etc) must not contain any external TOAST pointers. Without
* this rule, we'd have to look inside each Datum when preparing a tuple
* for storage, which would be expensive and would fail to extend cleanly
* to new sorts of container types.
*
* However, we don't want to say that tuples represented as HeapTuples
* can't contain toasted fields, so instead this routine should be called
* when such a HeapTuple is being converted into a Datum.
*
* While we're at it, we decompress any compressed fields too. This is not
* necessary for correctness, but reflects an expectation that compression
* will be more effective if applied to the whole tuple not individual
* fields. We are not so concerned about that that we want to deconstruct
* and reconstruct tuples just to get rid of compressed fields, however.
* So callers typically won't call this unless they see that the tuple has
* at least one external field.
*
* On the other hand, in-line short-header varlena fields are left alone.
* If we "untoasted" them here, they'd just get changed back to short-header
* format anyway within heap_fill_tuple.
* ----------
*/
Datum
toast_flatten_tuple_to_datum(HeapTupleHeader tup,
uint32 tup_len,
TupleDesc tupleDesc)
{
HeapTupleHeader new_data;
int32 new_header_len;
int32 new_data_len;
int32 new_tuple_len;
HeapTupleData tmptup;
int numAttrs = tupleDesc->natts;
int i;
bool has_nulls = false;
Datum toast_values[MaxTupleAttributeNumber];
bool toast_isnull[MaxTupleAttributeNumber];
bool toast_free[MaxTupleAttributeNumber];
/* Build a temporary HeapTuple control structure */
tmptup.t_len = tup_len;
ItemPointerSetInvalid(&(tmptup.t_self));
tmptup.t_tableOid = InvalidOid;
tmptup.t_data = tup;
/*
* Break down the tuple into fields.
*/
Assert(numAttrs <= MaxTupleAttributeNumber);
heap_deform_tuple(&tmptup, tupleDesc, toast_values, toast_isnull);
memset(toast_free, 0, numAttrs * sizeof(bool));
for (i = 0; i < numAttrs; i++)
{
/*
* Look at non-null varlena attributes
*/
if (toast_isnull[i])
has_nulls = true;
else if (TupleDescAttr(tupleDesc, i)->attlen == -1)
{
struct varlena *new_value;
new_value = (struct varlena *) DatumGetPointer(toast_values[i]);
if (VARATT_IS_EXTERNAL(new_value) ||
VARATT_IS_COMPRESSED(new_value))
{
new_value = detoast_attr(new_value);
toast_values[i] = PointerGetDatum(new_value);
toast_free[i] = true;
}
}
}
/*
* Calculate the new size of the tuple.
*
* This should match the reconstruction code in
* heap_toast_insert_or_update.
*/
new_header_len = SizeofHeapTupleHeader;
if (has_nulls)
new_header_len += BITMAPLEN(numAttrs);
new_header_len = MAXALIGN(new_header_len);
new_data_len = heap_compute_data_size(tupleDesc,
toast_values, toast_isnull);
new_tuple_len = new_header_len + new_data_len;
new_data = (HeapTupleHeader) palloc0(new_tuple_len);
/*
* Copy the existing tuple header, but adjust natts and t_hoff.
*/
memcpy(new_data, tup, SizeofHeapTupleHeader);
HeapTupleHeaderSetNatts(new_data, numAttrs);
new_data->t_hoff = new_header_len;
/* Set the composite-Datum header fields correctly */
HeapTupleHeaderSetDatumLength(new_data, new_tuple_len);
HeapTupleHeaderSetTypeId(new_data, tupleDesc->tdtypeid);
HeapTupleHeaderSetTypMod(new_data, tupleDesc->tdtypmod);
/* Copy over the data, and fill the null bitmap if needed */
heap_fill_tuple(tupleDesc,
toast_values,
toast_isnull,
(char *) new_data + new_header_len,
new_data_len,
&(new_data->t_infomask),
has_nulls ? new_data->t_bits : NULL);
/*
* Free allocated temp values
*/
for (i = 0; i < numAttrs; i++)
if (toast_free[i])
pfree(DatumGetPointer(toast_values[i]));
return PointerGetDatum(new_data);
}
/* ----------
* toast_build_flattened_tuple -
*
* Build a tuple containing no out-of-line toasted fields.
* (This does not eliminate compressed or short-header datums.)
*
* This is essentially just like heap_form_tuple, except that it will
* expand any external-data pointers beforehand.
*
* It's not very clear whether it would be preferable to decompress
* in-line compressed datums while at it. For now, we don't.
* ----------
*/
HeapTuple
toast_build_flattened_tuple(TupleDesc tupleDesc,
Datum *values,
bool *isnull)
{
HeapTuple new_tuple;
int numAttrs = tupleDesc->natts;
int num_to_free;
int i;
Datum new_values[MaxTupleAttributeNumber];
Pointer freeable_values[MaxTupleAttributeNumber];
/*
* We can pass the caller's isnull array directly to heap_form_tuple, but
* we potentially need to modify the values array.
*/
Assert(numAttrs <= MaxTupleAttributeNumber);
memcpy(new_values, values, numAttrs * sizeof(Datum));
num_to_free = 0;
for (i = 0; i < numAttrs; i++)
{
/*
* Look at non-null varlena attributes
*/
if (!isnull[i] && TupleDescAttr(tupleDesc, i)->attlen == -1)
{
struct varlena *new_value;
new_value = (struct varlena *) DatumGetPointer(new_values[i]);
if (VARATT_IS_EXTERNAL(new_value))
{
new_value = detoast_external_attr(new_value);
new_values[i] = PointerGetDatum(new_value);
freeable_values[num_to_free++] = (Pointer) new_value;
}
}
}
/*
* Form the reconfigured tuple.
*/
new_tuple = heap_form_tuple(tupleDesc, new_values, isnull);
/*
* Free allocated temp values
*/
for (i = 0; i < num_to_free; i++)
pfree(freeable_values[i]);
return new_tuple;
}
/*
* Fetch a TOAST slice from a heap table.
*
* toastrel is the relation from which chunks are to be fetched.
* valueid identifies the TOAST value from which chunks are being fetched.
* attrsize is the total size of the TOAST value.
* sliceoffset is the byte offset within the TOAST value from which to fetch.
* slicelength is the number of bytes to be fetched from the TOAST value.
* result is the varlena into which the results should be written.
*/
void
heap_fetch_toast_slice(Relation toastrel, Oid valueid, int32 attrsize,
int32 sliceoffset, int32 slicelength,
struct varlena *result)
{
Relation *toastidxs;
ScanKeyData toastkey[3];
TupleDesc toasttupDesc = toastrel->rd_att;
int nscankeys;
SysScanDesc toastscan;
HeapTuple ttup;
int32 expectedchunk;
int32 totalchunks = ((attrsize - 1) / TOAST_MAX_CHUNK_SIZE) + 1;
int startchunk;
int endchunk;
int num_indexes;
int validIndex;
SnapshotData SnapshotToast;
/* Look for the valid index of toast relation */
validIndex = toast_open_indexes(toastrel,
AccessShareLock,
&toastidxs,
&num_indexes);
startchunk = sliceoffset / TOAST_MAX_CHUNK_SIZE;
endchunk = (sliceoffset + slicelength - 1) / TOAST_MAX_CHUNK_SIZE;
Assert(endchunk <= totalchunks);
/* Set up a scan key to fetch from the index. */
ScanKeyInit(&toastkey[0],
(AttrNumber) 1,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(valueid));
/*
* No additional condition if fetching all chunks. Otherwise, use an
* equality condition for one chunk, and a range condition otherwise.
*/
if (startchunk == 0 && endchunk == totalchunks - 1)
nscankeys = 1;
else if (startchunk == endchunk)
{
ScanKeyInit(&toastkey[1],
(AttrNumber) 2,
BTEqualStrategyNumber, F_INT4EQ,
Int32GetDatum(startchunk));
nscankeys = 2;
}
else
{
ScanKeyInit(&toastkey[1],
(AttrNumber) 2,
BTGreaterEqualStrategyNumber, F_INT4GE,
Int32GetDatum(startchunk));
ScanKeyInit(&toastkey[2],
(AttrNumber) 2,
BTLessEqualStrategyNumber, F_INT4LE,
Int32GetDatum(endchunk));
nscankeys = 3;
}
/* Prepare for scan */
init_toast_snapshot(&SnapshotToast);
toastscan = systable_beginscan_ordered(toastrel, toastidxs[validIndex],
&SnapshotToast, nscankeys, toastkey);
/*
* Read the chunks by index
*
* The index is on (valueid, chunkidx) so they will come in order
*/
expectedchunk = startchunk;
while ((ttup = systable_getnext_ordered(toastscan, ForwardScanDirection)) != NULL)
{
int32 curchunk;
Pointer chunk;
bool isnull;
char *chunkdata;
int32 chunksize;
int32 expected_size;
int32 chcpystrt;
int32 chcpyend;
/*
* Have a chunk, extract the sequence number and the data
*/
curchunk = DatumGetInt32(fastgetattr(ttup, 2, toasttupDesc, &isnull));
Assert(!isnull);
chunk = DatumGetPointer(fastgetattr(ttup, 3, toasttupDesc, &isnull));
Assert(!isnull);
if (!VARATT_IS_EXTENDED(chunk))
{
chunksize = VARSIZE(chunk) - VARHDRSZ;
chunkdata = VARDATA(chunk);
}
else if (VARATT_IS_SHORT(chunk))
{
/* could happen due to heap_form_tuple doing its thing */
chunksize = VARSIZE_SHORT(chunk) - VARHDRSZ_SHORT;
chunkdata = VARDATA_SHORT(chunk);
}
else
{
/* should never happen */
elog(ERROR, "found toasted toast chunk for toast value %u in %s",
valueid, RelationGetRelationName(toastrel));
chunksize = 0; /* keep compiler quiet */
chunkdata = NULL;
}
/*
* Some checks on the data we've found
*/
if (curchunk != expectedchunk)
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg_internal("unexpected chunk number %d (expected %d) for toast value %u in %s",
curchunk, expectedchunk, valueid,
RelationGetRelationName(toastrel))));
if (curchunk > endchunk)
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg_internal("unexpected chunk number %d (out of range %d..%d) for toast value %u in %s",
curchunk,
startchunk, endchunk, valueid,
RelationGetRelationName(toastrel))));
expected_size = curchunk < totalchunks - 1 ? TOAST_MAX_CHUNK_SIZE
: attrsize - ((totalchunks - 1) * TOAST_MAX_CHUNK_SIZE);
if (chunksize != expected_size)
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg_internal("unexpected chunk size %d (expected %d) in chunk %d of %d for toast value %u in %s",
chunksize, expected_size,
curchunk, totalchunks, valueid,
RelationGetRelationName(toastrel))));
/*
* Copy the data into proper place in our result
*/
chcpystrt = 0;
chcpyend = chunksize - 1;
if (curchunk == startchunk)
chcpystrt = sliceoffset % TOAST_MAX_CHUNK_SIZE;
if (curchunk == endchunk)
chcpyend = (sliceoffset + slicelength - 1) % TOAST_MAX_CHUNK_SIZE;
memcpy(VARDATA(result) +
(curchunk * TOAST_MAX_CHUNK_SIZE - sliceoffset) + chcpystrt,
chunkdata + chcpystrt,
(chcpyend - chcpystrt) + 1);
expectedchunk++;
}
/*
* Final checks that we successfully fetched the datum
*/
if (expectedchunk != (endchunk + 1))
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg_internal("missing chunk number %d for toast value %u in %s",
expectedchunk, valueid,
RelationGetRelationName(toastrel))));
/* End scan and close indexes. */
systable_endscan_ordered(toastscan);
toast_close_indexes(toastidxs, num_indexes, AccessShareLock);
}
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