static struct varlena *toast_fetch_datum_slice(struct varlena *attr,
int32 sliceoffset,
int32 slicelength);
+static void heap_fetch_toast_slice(Relation toastrel, Oid valueid,
+ int32 attrsize, int32 sliceoffset,
+ int32 slicelength, struct varlena *result);
static struct varlena *toast_decompress_datum(struct varlena *attr);
static struct varlena *toast_decompress_datum_slice(struct varlena *attr, int32 slicelength);
toast_fetch_datum(struct varlena *attr)
{
Relation toastrel;
- Relation *toastidxs;
- ScanKeyData toastkey;
- SysScanDesc toastscan;
- HeapTuple ttup;
- TupleDesc toasttupDesc;
struct varlena *result;
struct varatt_external toast_pointer;
int32 attrsize;
- int32 expectedchunk;
- int32 totalchunks;
- int num_indexes;
- int validIndex;
- SnapshotData SnapshotToast;
if (!VARATT_IS_EXTERNAL_ONDISK(attr))
elog(ERROR, "toast_fetch_datum shouldn't be called for non-ondisk datums");
VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
attrsize = toast_pointer.va_extsize;
- totalchunks = ((attrsize - 1) / TOAST_MAX_CHUNK_SIZE) + 1;
result = (struct varlena *) palloc(attrsize + VARHDRSZ);
else
SET_VARSIZE(result, attrsize + VARHDRSZ);
+ if (attrsize == 0)
+ return result; /* Probably shouldn't happen, but just in case. */
+
/*
* Open the toast relation and its indexes
*/
toastrel = table_open(toast_pointer.va_toastrelid, AccessShareLock);
- toasttupDesc = toastrel->rd_att;
-
- /* Look for the valid index of the toast relation */
- validIndex = toast_open_indexes(toastrel,
- AccessShareLock,
- &toastidxs,
- &num_indexes);
- /*
- * Setup a scan key to fetch from the index by va_valueid
- */
- ScanKeyInit(&toastkey,
- (AttrNumber) 1,
- BTEqualStrategyNumber, F_OIDEQ,
- ObjectIdGetDatum(toast_pointer.va_valueid));
+ /* Fetch all chunks */
+ heap_fetch_toast_slice(toastrel, toast_pointer.va_valueid, attrsize, 0,
+ attrsize, result);
- /*
- * Read the chunks by index
- *
- * Note that because the index is actually on (valueid, chunkidx) we will
- * see the chunks in chunkidx order, even though we didn't explicitly ask
- * for it.
- */
- expectedchunk = 0;
-
- init_toast_snapshot(&SnapshotToast);
- toastscan = systable_beginscan_ordered(toastrel, toastidxs[validIndex],
- &SnapshotToast, 1, &toastkey);
- while ((ttup = systable_getnext_ordered(toastscan, ForwardScanDirection)) != NULL)
- {
- int32 curchunk;
- Pointer chunk;
- bool isnull;
- char *chunkdata;
- int32 chunksize;
- int32 expected_size;
-
- /*
- * 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",
- toast_pointer.va_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,
- toast_pointer.va_valueid,
- RelationGetRelationName(toastrel))));
- if (curchunk > totalchunks - 1)
- ereport(ERROR,
- (errcode(ERRCODE_DATA_CORRUPTED),
- errmsg_internal("unexpected chunk number %d (out of range %d..%d) for toast value %u in %s",
- curchunk,
- 0, totalchunks - 1,
- toast_pointer.va_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,
- toast_pointer.va_valueid,
- RelationGetRelationName(toastrel))));
-
- /*
- * Copy the data into proper place in our result
- */
- memcpy(VARDATA(result) + curchunk * TOAST_MAX_CHUNK_SIZE,
- chunkdata,
- chunksize);
-
- expectedchunk++;
- }
-
- /*
- * Final checks that we successfully fetched the datum
- */
- if (expectedchunk != totalchunks)
- ereport(ERROR,
- (errcode(ERRCODE_DATA_CORRUPTED),
- errmsg_internal("missing chunk number %d for toast value %u in %s",
- expectedchunk,
- toast_pointer.va_valueid,
- RelationGetRelationName(toastrel))));
-
- /*
- * End scan and close relations
- */
- systable_endscan_ordered(toastscan);
- toast_close_indexes(toastidxs, num_indexes, AccessShareLock);
+ /* Close toast table */
table_close(toastrel, AccessShareLock);
return result;
int32 slicelength)
{
Relation toastrel;
- Relation *toastidxs;
- ScanKeyData toastkey[3];
- int nscankeys;
- SysScanDesc toastscan;
- HeapTuple ttup;
- TupleDesc toasttupDesc;
struct varlena *result;
struct varatt_external toast_pointer;
int32 attrsize;
- int32 expectedchunk;
- int startchunk;
- int endchunk;
- int totalchunks;
- int num_indexes;
- int validIndex;
- SnapshotData SnapshotToast;
if (!VARATT_IS_EXTERNAL_ONDISK(attr))
elog(ERROR, "toast_fetch_datum_slice shouldn't be called for non-ondisk datums");
Assert(!VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer) || 0 == sliceoffset);
attrsize = toast_pointer.va_extsize;
- totalchunks = ((attrsize - 1) / TOAST_MAX_CHUNK_SIZE) + 1;
if (sliceoffset >= attrsize)
{
if (slicelength == 0)
return result; /* Can save a lot of work at this point! */
- startchunk = sliceoffset / TOAST_MAX_CHUNK_SIZE;
- endchunk = (sliceoffset + slicelength - 1) / TOAST_MAX_CHUNK_SIZE;
- Assert(endchunk < totalchunks);
-
- /*
- * Open the toast relation and its indexes
- */
+ /* Open the toast relation */
toastrel = table_open(toast_pointer.va_toastrelid, AccessShareLock);
- toasttupDesc = toastrel->rd_att;
+
+ /* Fetch all chunks */
+ heap_fetch_toast_slice(toastrel, toast_pointer.va_valueid, attrsize,
+ sliceoffset, slicelength, result);
+
+ /* Close toast table */
+ table_close(toastrel, AccessShareLock);
+
+ return result;
+}
+
+/*
+ * 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.
+ */
+static 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,
&toastidxs,
&num_indexes);
+ startchunk = sliceoffset / TOAST_MAX_CHUNK_SIZE;
+ endchunk = (sliceoffset + slicelength - 1) / TOAST_MAX_CHUNK_SIZE;
+ Assert(endchunk <= totalchunks);
+
/*
* Setup a scan key to fetch from the index. This is either two keys or
* three depending on the number of chunks.
ScanKeyInit(&toastkey[0],
(AttrNumber) 1,
BTEqualStrategyNumber, F_OIDEQ,
- ObjectIdGetDatum(toast_pointer.va_valueid));
+ ObjectIdGetDatum(valueid));
/*
- * Use equality condition for one chunk, a range condition otherwise:
+ * No additional condition if fetching all chunks. Otherwise, use an
+ * equality condition for one chunk, and a range condition otherwise.
*/
- if (startchunk == endchunk)
+ if (startchunk == 0 && endchunk == totalchunks - 1)
+ nscankeys = 1;
+ else if (startchunk == endchunk)
{
ScanKeyInit(&toastkey[1],
(AttrNumber) 2,
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
*/
- init_toast_snapshot(&SnapshotToast);
expectedchunk = startchunk;
- toastscan = systable_beginscan_ordered(toastrel, toastidxs[validIndex],
- &SnapshotToast, nscankeys, toastkey);
while ((ttup = systable_getnext_ordered(toastscan, ForwardScanDirection)) != NULL)
{
int32 curchunk;
{
/* should never happen */
elog(ERROR, "found toasted toast chunk for toast value %u in %s",
- toast_pointer.va_valueid,
- RelationGetRelationName(toastrel));
+ valueid, RelationGetRelationName(toastrel));
chunksize = 0; /* keep compiler quiet */
chunkdata = NULL;
}
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg_internal("unexpected chunk number %d (expected %d) for toast value %u in %s",
- curchunk, expectedchunk,
- toast_pointer.va_valueid,
+ 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,
- toast_pointer.va_valueid,
+ startchunk, endchunk, valueid,
RelationGetRelationName(toastrel))));
expected_size = curchunk < totalchunks - 1 ? TOAST_MAX_CHUNK_SIZE
: attrsize - ((totalchunks - 1) * TOAST_MAX_CHUNK_SIZE);
(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,
- toast_pointer.va_valueid,
+ curchunk, totalchunks, valueid,
RelationGetRelationName(toastrel))));
/*
ereport(ERROR,
(errcode(ERRCODE_DATA_CORRUPTED),
errmsg_internal("missing chunk number %d for toast value %u in %s",
- expectedchunk,
- toast_pointer.va_valueid,
+ expectedchunk, valueid,
RelationGetRelationName(toastrel))));
- /*
- * End scan and close relations
- */
+ /* End scan and close indexes. */
systable_endscan_ordered(toastscan);
toast_close_indexes(toastidxs, num_indexes, AccessShareLock);
- table_close(toastrel, AccessShareLock);
-
- return result;
}
/* ----------
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