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Diffstat (limited to 'src/backend/access/heap/heaptoast.c')
| -rw-r--r-- | src/backend/access/heap/heaptoast.c | 793 |
1 files changed, 793 insertions, 0 deletions
diff --git a/src/backend/access/heap/heaptoast.c b/src/backend/access/heap/heaptoast.c new file mode 100644 index 0000000..1575a81 --- /dev/null +++ b/src/backend/access/heap/heaptoast.c @@ -0,0 +1,793 @@ +/*------------------------------------------------------------------------- + * + * heaptoast.c + * Heap-specific definitions for external and compressed storage + * of variable size attributes. + * + * Copyright (c) 2000-2022, 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); +} |