/*------------------------------------------------------------------------- * * tuptoaster.c * Support routines for external and compressed storage of * variable size attributes. * * Copyright (c) 2000-2009, PostgreSQL Global Development Group * * * IDENTIFICATION * $PostgreSQL: pgsql/src/backend/access/heap/tuptoaster.c,v 1.93 2009/06/11 14:48:54 momjian Exp $ * * * INTERFACE ROUTINES * toast_insert_or_update - * Try to make a given tuple fit into one page by compressing * or moving off attributes * * toast_delete - * Reclaim toast storage when a tuple is deleted * * heap_tuple_untoast_attr - * Fetch back a given value from the "secondary" relation * *------------------------------------------------------------------------- */ #include "postgres.h" #include #include #include "access/genam.h" #include "access/heapam.h" #include "access/tuptoaster.h" #include "access/xact.h" #include "catalog/catalog.h" #include "utils/fmgroids.h" #include "utils/pg_lzcompress.h" #include "utils/rel.h" #include "utils/typcache.h" #include "utils/tqual.h" #undef TOAST_DEBUG /* Size of an EXTERNAL datum that contains a standard TOAST pointer */ #define TOAST_POINTER_SIZE (VARHDRSZ_EXTERNAL + sizeof(struct varatt_external)) /* * Testing whether an externally-stored value is compressed now requires * comparing extsize (the actual length of the external data) to rawsize * (the original uncompressed datum's size). The latter includes VARHDRSZ * overhead, the former doesn't. We never use compression unless it actually * saves space, so we expect either equality or less-than. */ #define VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer) \ ((toast_pointer).va_extsize < (toast_pointer).va_rawsize - VARHDRSZ) /* * Macro to fetch the possibly-unaligned contents of an EXTERNAL datum * into a local "struct varatt_external" toast pointer. This should be * just a memcpy, but some versions of gcc seem to produce broken code * that assumes the datum contents are aligned. Introducing an explicit * intermediate "varattrib_1b_e *" variable seems to fix it. */ #define VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr) \ do { \ varattrib_1b_e *attre = (varattrib_1b_e *) (attr); \ Assert(VARATT_IS_EXTERNAL(attre)); \ Assert(VARSIZE_EXTERNAL(attre) == sizeof(toast_pointer) + VARHDRSZ_EXTERNAL); \ memcpy(&(toast_pointer), VARDATA_EXTERNAL(attre), sizeof(toast_pointer)); \ } while (0) static void toast_delete_datum(Relation rel, Datum value); static Datum toast_save_datum(Relation rel, Datum value, int options); static struct varlena *toast_fetch_datum(struct varlena * attr); static struct varlena *toast_fetch_datum_slice(struct varlena * attr, int32 sliceoffset, int32 length); /* ---------- * heap_tuple_fetch_attr - * * Public entry point to get back a toasted value from * external storage (possibly still in compressed format). * * This will return a datum that contains all the data internally, ie, not * relying on external storage, but it can still be compressed or have a short * header. ---------- */ struct varlena * heap_tuple_fetch_attr(struct varlena * attr) { struct varlena *result; if (VARATT_IS_EXTERNAL(attr)) { /* * This is an external stored plain value */ result = toast_fetch_datum(attr); } else { /* * This is a plain value inside of the main tuple - why am I called? */ result = attr; } return result; } /* ---------- * heap_tuple_untoast_attr - * * Public entry point to get back a toasted value from compression * or external storage. * ---------- */ struct varlena * heap_tuple_untoast_attr(struct varlena * attr) { if (VARATT_IS_EXTERNAL(attr)) { /* * This is an externally stored datum --- fetch it back from there */ attr = toast_fetch_datum(attr); /* If it's compressed, decompress it */ if (VARATT_IS_COMPRESSED(attr)) { PGLZ_Header *tmp = (PGLZ_Header *) attr; attr = (struct varlena *) palloc(PGLZ_RAW_SIZE(tmp) + VARHDRSZ); SET_VARSIZE(attr, PGLZ_RAW_SIZE(tmp) + VARHDRSZ); pglz_decompress(tmp, VARDATA(attr)); pfree(tmp); } } else if (VARATT_IS_COMPRESSED(attr)) { /* * This is a compressed value inside of the main tuple */ PGLZ_Header *tmp = (PGLZ_Header *) attr; attr = (struct varlena *) palloc(PGLZ_RAW_SIZE(tmp) + VARHDRSZ); SET_VARSIZE(attr, PGLZ_RAW_SIZE(tmp) + VARHDRSZ); pglz_decompress(tmp, VARDATA(attr)); } else if (VARATT_IS_SHORT(attr)) { /* * This is a short-header varlena --- convert to 4-byte header format */ Size data_size = VARSIZE_SHORT(attr) - VARHDRSZ_SHORT; Size new_size = data_size + VARHDRSZ; struct varlena *new_attr; new_attr = (struct varlena *) palloc(new_size); SET_VARSIZE(new_attr, new_size); memcpy(VARDATA(new_attr), VARDATA_SHORT(attr), data_size); attr = new_attr; } return attr; } /* ---------- * heap_tuple_untoast_attr_slice - * * Public entry point to get back part of a toasted value * from compression or external storage. * ---------- */ struct varlena * heap_tuple_untoast_attr_slice(struct varlena * attr, int32 sliceoffset, int32 slicelength) { struct varlena *preslice; struct varlena *result; char *attrdata; int32 attrsize; if (VARATT_IS_EXTERNAL(attr)) { struct varatt_external toast_pointer; VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr); /* fast path for non-compressed external datums */ if (!VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer)) return toast_fetch_datum_slice(attr, sliceoffset, slicelength); /* fetch it back (compressed marker will get set automatically) */ preslice = toast_fetch_datum(attr); } else preslice = attr; if (VARATT_IS_COMPRESSED(preslice)) { PGLZ_Header *tmp = (PGLZ_Header *) preslice; Size size = PGLZ_RAW_SIZE(tmp) + VARHDRSZ; preslice = (struct varlena *) palloc(size); SET_VARSIZE(preslice, size); pglz_decompress(tmp, VARDATA(preslice)); if (tmp != (PGLZ_Header *) attr) pfree(tmp); } if (VARATT_IS_SHORT(preslice)) { attrdata = VARDATA_SHORT(preslice); attrsize = VARSIZE_SHORT(preslice) - VARHDRSZ_SHORT; } else { attrdata = VARDATA(preslice); attrsize = VARSIZE(preslice) - VARHDRSZ; } /* slicing of datum for compressed cases and plain value */ if (sliceoffset >= attrsize) { sliceoffset = 0; slicelength = 0; } if (((sliceoffset + slicelength) > attrsize) || slicelength < 0) slicelength = attrsize - sliceoffset; result = (struct varlena *) palloc(slicelength + VARHDRSZ); SET_VARSIZE(result, slicelength + VARHDRSZ); memcpy(VARDATA(result), attrdata + sliceoffset, slicelength); if (preslice != attr) pfree(preslice); return result; } /* ---------- * toast_raw_datum_size - * * Return the raw (detoasted) size of a varlena datum * (including the VARHDRSZ header) * ---------- */ Size toast_raw_datum_size(Datum value) { struct varlena *attr = (struct varlena *) DatumGetPointer(value); Size result; if (VARATT_IS_EXTERNAL(attr)) { /* va_rawsize is the size of the original datum -- including header */ struct varatt_external toast_pointer; VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr); result = toast_pointer.va_rawsize; } else if (VARATT_IS_COMPRESSED(attr)) { /* here, va_rawsize is just the payload size */ result = VARRAWSIZE_4B_C(attr) + VARHDRSZ; } else if (VARATT_IS_SHORT(attr)) { /* * we have to normalize the header length to VARHDRSZ or else the * callers of this function will be confused. */ result = VARSIZE_SHORT(attr) - VARHDRSZ_SHORT + VARHDRSZ; } else { /* plain untoasted datum */ result = VARSIZE(attr); } return result; } /* ---------- * toast_datum_size * * Return the physical storage size (possibly compressed) of a varlena datum * ---------- */ Size toast_datum_size(Datum value) { struct varlena *attr = (struct varlena *) DatumGetPointer(value); Size result; if (VARATT_IS_EXTERNAL(attr)) { /* * Attribute is stored externally - return the extsize whether * compressed or not. We do not count the size of the toast pointer * ... should we? */ struct varatt_external toast_pointer; VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr); result = toast_pointer.va_extsize; } else if (VARATT_IS_SHORT(attr)) { result = VARSIZE_SHORT(attr); } else { /* * Attribute is stored inline either compressed or not, just calculate * the size of the datum in either case. */ result = VARSIZE(attr); } return result; } /* ---------- * toast_delete - * * Cascaded delete toast-entries on DELETE * ---------- */ void toast_delete(Relation rel, HeapTuple oldtup) { TupleDesc tupleDesc; Form_pg_attribute *att; int numAttrs; int i; Datum toast_values[MaxHeapAttributeNumber]; bool toast_isnull[MaxHeapAttributeNumber]; /* * We should only ever be called for tuples of plain relations --- * recursing on a toast rel is bad news. */ Assert(rel->rd_rel->relkind == RELKIND_RELATION); /* * 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; att = tupleDesc->attrs; numAttrs = tupleDesc->natts; Assert(numAttrs <= MaxHeapAttributeNumber); heap_deform_tuple(oldtup, tupleDesc, toast_values, toast_isnull); /* * Check for external stored attributes and delete them from the secondary * relation. */ for (i = 0; i < numAttrs; i++) { if (att[i]->attlen == -1) { Datum value = toast_values[i]; if (!toast_isnull[i] && VARATT_IS_EXTERNAL(PointerGetDatum(value))) toast_delete_datum(rel, value); } } } /* ---------- * 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 toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup, int options) { HeapTuple result_tuple; TupleDesc tupleDesc; Form_pg_attribute *att; int numAttrs; int i; bool need_change = false; bool need_free = false; bool need_delold = false; bool has_nulls = false; Size maxDataLen; Size hoff; char toast_action[MaxHeapAttributeNumber]; bool toast_isnull[MaxHeapAttributeNumber]; bool toast_oldisnull[MaxHeapAttributeNumber]; Datum toast_values[MaxHeapAttributeNumber]; Datum toast_oldvalues[MaxHeapAttributeNumber]; int32 toast_sizes[MaxHeapAttributeNumber]; bool toast_free[MaxHeapAttributeNumber]; bool toast_delold[MaxHeapAttributeNumber]; /* * We should only ever be called for tuples of plain relations --- * recursing on a toast rel is bad news. */ Assert(rel->rd_rel->relkind == RELKIND_RELATION); /* * Get the tuple descriptor and break down the tuple(s) into fields. */ tupleDesc = rel->rd_att; att = tupleDesc->attrs; 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); /* ---------- * Then collect information about the values given * * NOTE: toast_action[i] can have these values: * ' ' default handling * 'p' already processed --- don't touch it * 'x' incompressible, but OK to move off * * NOTE: toast_sizes[i] is only made valid for varlena attributes with * toast_action[i] different from 'p'. * ---------- */ memset(toast_action, ' ', numAttrs * sizeof(char)); memset(toast_free, 0, numAttrs * sizeof(bool)); memset(toast_delold, 0, numAttrs * sizeof(bool)); for (i = 0; i < numAttrs; i++) { struct varlena *old_value; struct varlena *new_value; if (oldtup != NULL) { /* * For UPDATE get the old and new values of this attribute */ old_value = (struct varlena *) DatumGetPointer(toast_oldvalues[i]); new_value = (struct varlena *) DatumGetPointer(toast_values[i]); /* * If the old value is an external stored one, check if it has * changed so we have to delete it later. */ if (att[i]->attlen == -1 && !toast_oldisnull[i] && VARATT_IS_EXTERNAL(old_value)) { if (toast_isnull[i] || !VARATT_IS_EXTERNAL(new_value) || memcmp((char *) old_value, (char *) new_value, VARSIZE_EXTERNAL(old_value)) != 0) { /* * The old external stored value isn't needed any more * after the update */ toast_delold[i] = true; need_delold = true; } else { /* * This attribute isn't changed by this update so we reuse * the original reference to the old value in the new * tuple. */ toast_action[i] = 'p'; continue; } } } else { /* * For INSERT simply get the new value */ new_value = (struct varlena *) DatumGetPointer(toast_values[i]); } /* * Handle NULL attributes */ if (toast_isnull[i]) { toast_action[i] = 'p'; has_nulls = true; continue; } /* * Now look at varlena attributes */ if (att[i]->attlen == -1) { /* * If the table's attribute says PLAIN always, force it so. */ if (att[i]->attstorage == 'p') toast_action[i] = 'p'; /* * We took care of UPDATE above, so any external value we find * still in the tuple must be someone else's we cannot reuse. * Fetch it back (without decompression, unless we are forcing * PLAIN storage). If necessary, we'll push it out as a new * external value below. */ if (VARATT_IS_EXTERNAL(new_value)) { if (att[i]->attstorage == 'p') new_value = heap_tuple_untoast_attr(new_value); else new_value = heap_tuple_fetch_attr(new_value); toast_values[i] = PointerGetDatum(new_value); toast_free[i] = true; need_change = true; need_free = true; } /* * Remember the size of this attribute */ toast_sizes[i] = VARSIZE_ANY(new_value); } else { /* * Not a varlena attribute, plain storage always */ toast_action[i] = 'p'; } } /* ---------- * Compress and/or save external until data fits into target length * * 1: Inline compress attributes with attstorage 'x', and store very * large attributes with attstorage 'x' or 'e' external immediately * 2: Store attributes with attstorage 'x' or 'e' external * 3: Inline compress attributes with attstorage 'm' * 4: Store attributes with attstorage 'm' external * ---------- */ /* compute header overhead --- this should match heap_form_tuple() */ hoff = offsetof(HeapTupleHeaderData, t_bits); if (has_nulls) hoff += BITMAPLEN(numAttrs); if (newtup->t_data->t_infomask & HEAP_HASOID) hoff += sizeof(Oid); hoff = MAXALIGN(hoff); Assert(hoff == newtup->t_data->t_hoff); /* now convert to a limit on the tuple data size */ maxDataLen = TOAST_TUPLE_TARGET - hoff; /* * Look for attributes with attstorage 'x' to compress. Also find large * attributes with attstorage 'x' or 'e', and store them external. */ while (heap_compute_data_size(tupleDesc, toast_values, toast_isnull) > maxDataLen) { int biggest_attno = -1; int32 biggest_size = MAXALIGN(TOAST_POINTER_SIZE); Datum old_value; Datum new_value; /* * Search for the biggest yet unprocessed internal attribute */ for (i = 0; i < numAttrs; i++) { if (toast_action[i] != ' ') continue; if (VARATT_IS_EXTERNAL(DatumGetPointer(toast_values[i]))) continue; /* can't happen, toast_action would be 'p' */ if (VARATT_IS_COMPRESSED(DatumGetPointer(toast_values[i]))) continue; if (att[i]->attstorage != 'x' && att[i]->attstorage != 'e') continue; if (toast_sizes[i] > biggest_size) { biggest_attno = i; biggest_size = toast_sizes[i]; } } if (biggest_attno < 0) break; /* * Attempt to compress it inline, if it has attstorage 'x' */ i = biggest_attno; if (att[i]->attstorage == 'x') { old_value = toast_values[i]; new_value = toast_compress_datum(old_value); if (DatumGetPointer(new_value) != NULL) { /* successful compression */ if (toast_free[i]) pfree(DatumGetPointer(old_value)); toast_values[i] = new_value; toast_free[i] = true; toast_sizes[i] = VARSIZE(DatumGetPointer(toast_values[i])); need_change = true; need_free = true; } else { /* incompressible, ignore on subsequent compression passes */ toast_action[i] = 'x'; } } else { /* has attstorage 'e', ignore on subsequent compression passes */ toast_action[i] = 'x'; } /* * 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_sizes[i] > maxDataLen && rel->rd_rel->reltoastrelid != InvalidOid) { old_value = toast_values[i]; toast_action[i] = 'p'; toast_values[i] = toast_save_datum(rel, toast_values[i], options); if (toast_free[i]) pfree(DatumGetPointer(old_value)); toast_free[i] = true; need_change = true; need_free = true; } } /* * Second we look for attributes of attstorage 'x' or 'e' that are still * inline. 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 = -1; int32 biggest_size = MAXALIGN(TOAST_POINTER_SIZE); Datum old_value; /*------ * Search for the biggest yet inlined attribute with * attstorage equals 'x' or 'e' *------ */ for (i = 0; i < numAttrs; i++) { if (toast_action[i] == 'p') continue; if (VARATT_IS_EXTERNAL(DatumGetPointer(toast_values[i]))) continue; /* can't happen, toast_action would be 'p' */ if (att[i]->attstorage != 'x' && att[i]->attstorage != 'e') continue; if (toast_sizes[i] > biggest_size) { biggest_attno = i; biggest_size = toast_sizes[i]; } } if (biggest_attno < 0) break; /* * Store this external */ i = biggest_attno; old_value = toast_values[i]; toast_action[i] = 'p'; toast_values[i] = toast_save_datum(rel, toast_values[i], options); if (toast_free[i]) pfree(DatumGetPointer(old_value)); toast_free[i] = true; need_change = true; need_free = true; } /* * Round 3 - this time we take attributes with storage 'm' into * compression */ while (heap_compute_data_size(tupleDesc, toast_values, toast_isnull) > maxDataLen) { int biggest_attno = -1; int32 biggest_size = MAXALIGN(TOAST_POINTER_SIZE); Datum old_value; Datum new_value; /* * Search for the biggest yet uncompressed internal attribute */ for (i = 0; i < numAttrs; i++) { if (toast_action[i] != ' ') continue; if (VARATT_IS_EXTERNAL(DatumGetPointer(toast_values[i]))) continue; /* can't happen, toast_action would be 'p' */ if (VARATT_IS_COMPRESSED(DatumGetPointer(toast_values[i]))) continue; if (att[i]->attstorage != 'm') continue; if (toast_sizes[i] > biggest_size) { biggest_attno = i; biggest_size = toast_sizes[i]; } } if (biggest_attno < 0) break; /* * Attempt to compress it inline */ i = biggest_attno; old_value = toast_values[i]; new_value = toast_compress_datum(old_value); if (DatumGetPointer(new_value) != NULL) { /* successful compression */ if (toast_free[i]) pfree(DatumGetPointer(old_value)); toast_values[i] = new_value; toast_free[i] = true; toast_sizes[i] = VARSIZE(DatumGetPointer(toast_values[i])); need_change = true; need_free = true; } else { /* incompressible, ignore on subsequent compression passes */ toast_action[i] = 'x'; } } /* * Finally we store attributes of type 'm' external, if possible. */ while (heap_compute_data_size(tupleDesc, toast_values, toast_isnull) > maxDataLen && rel->rd_rel->reltoastrelid != InvalidOid) { int biggest_attno = -1; int32 biggest_size = MAXALIGN(TOAST_POINTER_SIZE); Datum old_value; /*-------- * Search for the biggest yet inlined attribute with * attstorage = 'm' *-------- */ for (i = 0; i < numAttrs; i++) { if (toast_action[i] == 'p') continue; if (VARATT_IS_EXTERNAL(DatumGetPointer(toast_values[i]))) continue; /* can't happen, toast_action would be 'p' */ if (att[i]->attstorage != 'm') continue; if (toast_sizes[i] > biggest_size) { biggest_attno = i; biggest_size = toast_sizes[i]; } } if (biggest_attno < 0) break; /* * Store this external */ i = biggest_attno; old_value = toast_values[i]; toast_action[i] = 'p'; toast_values[i] = toast_save_datum(rel, toast_values[i], options); if (toast_free[i]) pfree(DatumGetPointer(old_value)); toast_free[i] = true; need_change = true; need_free = true; } /* * In the case we toasted any values, we need to build a new heap tuple * with the changed values. */ if (need_change) { HeapTupleHeader olddata = newtup->t_data; HeapTupleHeader new_data; int32 new_len; int32 new_data_len; /* * Calculate the new size of the tuple. Header size should not * change, but data size might. */ new_len = offsetof(HeapTupleHeaderData, t_bits); if (has_nulls) new_len += BITMAPLEN(numAttrs); if (olddata->t_infomask & HEAP_HASOID) new_len += sizeof(Oid); new_len = MAXALIGN(new_len); Assert(new_len == olddata->t_hoff); new_data_len = heap_compute_data_size(tupleDesc, toast_values, toast_isnull); new_len += new_data_len; /* * Allocate and zero the space needed, and fill HeapTupleData fields. */ result_tuple = (HeapTuple) palloc0(HEAPTUPLESIZE + new_len); result_tuple->t_len = new_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; /* * Put the existing tuple header and the changed values into place */ memcpy(new_data, olddata, olddata->t_hoff); heap_fill_tuple(tupleDesc, toast_values, toast_isnull, (char *) new_data + olddata->t_hoff, new_data_len, &(new_data->t_infomask), has_nulls ? new_data->t_bits : NULL); } else result_tuple = newtup; /* * Free allocated temp values */ if (need_free) for (i = 0; i < numAttrs; i++) if (toast_free[i]) pfree(DatumGetPointer(toast_values[i])); /* * Delete external values from the old tuple */ if (need_delold) for (i = 0; i < numAttrs; i++) if (toast_delold[i]) toast_delete_datum(rel, toast_oldvalues[i]); return result_tuple; } /* ---------- * toast_flatten_tuple_attribute - * * If a Datum is of composite type, "flatten" it to contain no toasted fields. * This must be invoked on any potentially-composite field that is to be * inserted into a tuple. Doing this preserves the invariant that toasting * goes only one level deep in a tuple. * * Note that flattening does not mean expansion of short-header varlenas, * so in one sense toasting is allowed within composite datums. * ---------- */ Datum toast_flatten_tuple_attribute(Datum value, Oid typeId, int32 typeMod) { TupleDesc tupleDesc; HeapTupleHeader olddata; HeapTupleHeader new_data; int32 new_len; int32 new_data_len; HeapTupleData tmptup; Form_pg_attribute *att; int numAttrs; int i; bool need_change = false; bool has_nulls = false; Datum toast_values[MaxTupleAttributeNumber]; bool toast_isnull[MaxTupleAttributeNumber]; bool toast_free[MaxTupleAttributeNumber]; /* * See if it's a composite type, and get the tupdesc if so. */ tupleDesc = lookup_rowtype_tupdesc_noerror(typeId, typeMod, true); if (tupleDesc == NULL) return value; /* not a composite type */ att = tupleDesc->attrs; numAttrs = tupleDesc->natts; /* * Break down the tuple into fields. */ olddata = DatumGetHeapTupleHeader(value); Assert(typeId == HeapTupleHeaderGetTypeId(olddata)); Assert(typeMod == HeapTupleHeaderGetTypMod(olddata)); /* Build a temporary HeapTuple control structure */ tmptup.t_len = HeapTupleHeaderGetDatumLength(olddata); ItemPointerSetInvalid(&(tmptup.t_self)); tmptup.t_tableOid = InvalidOid; tmptup.t_data = olddata; 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 (att[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 = heap_tuple_untoast_attr(new_value); toast_values[i] = PointerGetDatum(new_value); toast_free[i] = true; need_change = true; } } } /* * If nothing to untoast, just return the original tuple. */ if (!need_change) { ReleaseTupleDesc(tupleDesc); return value; } /* * Calculate the new size of the tuple. Header size should not change, * but data size might. */ new_len = offsetof(HeapTupleHeaderData, t_bits); if (has_nulls) new_len += BITMAPLEN(numAttrs); if (olddata->t_infomask & HEAP_HASOID) new_len += sizeof(Oid); new_len = MAXALIGN(new_len); Assert(new_len == olddata->t_hoff); new_data_len = heap_compute_data_size(tupleDesc, toast_values, toast_isnull); new_len += new_data_len; new_data = (HeapTupleHeader) palloc0(new_len); /* * Put the tuple header and the changed values into place */ memcpy(new_data, olddata, olddata->t_hoff); HeapTupleHeaderSetDatumLength(new_data, new_len); heap_fill_tuple(tupleDesc, toast_values, toast_isnull, (char *) new_data + olddata->t_hoff, 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])); ReleaseTupleDesc(tupleDesc); return PointerGetDatum(new_data); } /* ---------- * toast_compress_datum - * * Create a compressed version of a varlena datum * * If we fail (ie, compressed result is actually bigger than original) * then return NULL. We must not use compressed data if it'd expand * the tuple! * * We use VAR{SIZE,DATA}_ANY so we can handle short varlenas here without * copying them. But we can't handle external or compressed datums. * ---------- */ Datum toast_compress_datum(Datum value) { struct varlena *tmp; int32 valsize = VARSIZE_ANY_EXHDR(DatumGetPointer(value)); Assert(!VARATT_IS_EXTERNAL(DatumGetPointer(value))); Assert(!VARATT_IS_COMPRESSED(DatumGetPointer(value))); /* * No point in wasting a palloc cycle if value size is out of the allowed * range for compression */ if (valsize < PGLZ_strategy_default->min_input_size || valsize > PGLZ_strategy_default->max_input_size) return PointerGetDatum(NULL); tmp = (struct varlena *) palloc(PGLZ_MAX_OUTPUT(valsize)); /* * We recheck the actual size even if pglz_compress() reports success, * because it might be satisfied with having saved as little as one byte * in the compressed data --- which could turn into a net loss once you * consider header and alignment padding. Worst case, the compressed * format might require three padding bytes (plus header, which is * included in VARSIZE(tmp)), whereas the uncompressed format would take * only one header byte and no padding if the value is short enough. So * we insist on a savings of more than 2 bytes to ensure we have a gain. */ if (pglz_compress(VARDATA_ANY(DatumGetPointer(value)), valsize, (PGLZ_Header *) tmp, PGLZ_strategy_default) && VARSIZE(tmp) < valsize - 2) { /* successful compression */ return PointerGetDatum(tmp); } else { /* incompressible data */ pfree(tmp); return PointerGetDatum(NULL); } } /* ---------- * toast_save_datum - * * Save one single datum into the secondary relation and return * a Datum reference for it. * ---------- */ static Datum toast_save_datum(Relation rel, Datum value, int options) { Relation toastrel; Relation toastidx; HeapTuple toasttup; TupleDesc toasttupDesc; Datum t_values[3]; bool t_isnull[3]; CommandId mycid = GetCurrentCommandId(true); struct varlena *result; struct varatt_external toast_pointer; struct { struct varlena hdr; char data[TOAST_MAX_CHUNK_SIZE]; /* make struct big enough */ int32 align_it; /* ensure struct is aligned well enough */ } chunk_data; int32 chunk_size; int32 chunk_seq = 0; char *data_p; int32 data_todo; Pointer dval = DatumGetPointer(value); /* * Open the toast relation and its index. We can use the index to check * uniqueness of the OID we assign to the toasted item, even though it has * additional columns besides OID. */ toastrel = heap_open(rel->rd_rel->reltoastrelid, RowExclusiveLock); toasttupDesc = toastrel->rd_att; toastidx = index_open(toastrel->rd_rel->reltoastidxid, RowExclusiveLock); /* * Get the data pointer and length, and compute va_rawsize and va_extsize. * * va_rawsize is the size of the equivalent fully uncompressed datum, so * we have to adjust for short headers. * * va_extsize is the actual size of the data payload in the toast records. */ if (VARATT_IS_SHORT(dval)) { data_p = VARDATA_SHORT(dval); data_todo = VARSIZE_SHORT(dval) - VARHDRSZ_SHORT; toast_pointer.va_rawsize = data_todo + VARHDRSZ; /* as if not short */ toast_pointer.va_extsize = data_todo; } else if (VARATT_IS_COMPRESSED(dval)) { data_p = VARDATA(dval); data_todo = VARSIZE(dval) - VARHDRSZ; /* rawsize in a compressed datum is just the size of the payload */ toast_pointer.va_rawsize = VARRAWSIZE_4B_C(dval) + VARHDRSZ; toast_pointer.va_extsize = data_todo; /* Assert that the numbers look like it's compressed */ Assert(VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer)); } else { data_p = VARDATA(dval); data_todo = VARSIZE(dval) - VARHDRSZ; toast_pointer.va_rawsize = VARSIZE(dval); toast_pointer.va_extsize = data_todo; } toast_pointer.va_valueid = GetNewOidWithIndex(toastrel, RelationGetRelid(toastidx), (AttrNumber) 1); toast_pointer.va_toastrelid = rel->rd_rel->reltoastrelid; /* * Initialize constant parts of the tuple data */ t_values[0] = ObjectIdGetDatum(toast_pointer.va_valueid); t_values[2] = PointerGetDatum(&chunk_data); t_isnull[0] = false; t_isnull[1] = false; t_isnull[2] = false; /* * Split up the item into chunks */ while (data_todo > 0) { /* * Calculate the size of this chunk */ chunk_size = Min(TOAST_MAX_CHUNK_SIZE, data_todo); /* * Build a tuple and store it */ t_values[1] = Int32GetDatum(chunk_seq++); SET_VARSIZE(&chunk_data, chunk_size + VARHDRSZ); memcpy(VARDATA(&chunk_data), data_p, chunk_size); toasttup = heap_form_tuple(toasttupDesc, t_values, t_isnull); heap_insert(toastrel, toasttup, mycid, options, NULL); /* * Create the index entry. We cheat a little here by not using * FormIndexDatum: this relies on the knowledge that the index columns * are the same as the initial columns of the table. * * Note also that there had better not be any user-created index on * the TOAST table, since we don't bother to update anything else. */ index_insert(toastidx, t_values, t_isnull, &(toasttup->t_self), toastrel, toastidx->rd_index->indisunique); /* * Free memory */ heap_freetuple(toasttup); /* * Move on to next chunk */ data_todo -= chunk_size; data_p += chunk_size; } /* * Done - close toast relation */ index_close(toastidx, RowExclusiveLock); heap_close(toastrel, RowExclusiveLock); /* * Create the TOAST pointer value that we'll return */ result = (struct varlena *) palloc(TOAST_POINTER_SIZE); SET_VARSIZE_EXTERNAL(result, TOAST_POINTER_SIZE); memcpy(VARDATA_EXTERNAL(result), &toast_pointer, sizeof(toast_pointer)); return PointerGetDatum(result); } /* ---------- * toast_delete_datum - * * Delete a single external stored value. * ---------- */ static void toast_delete_datum(Relation rel, Datum value) { struct varlena *attr = (struct varlena *) DatumGetPointer(value); struct varatt_external toast_pointer; Relation toastrel; Relation toastidx; ScanKeyData toastkey; SysScanDesc toastscan; HeapTuple toasttup; if (!VARATT_IS_EXTERNAL(attr)) return; /* Must copy to access aligned fields */ VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr); /* * Open the toast relation and its index */ toastrel = heap_open(toast_pointer.va_toastrelid, RowExclusiveLock); toastidx = index_open(toastrel->rd_rel->reltoastidxid, RowExclusiveLock); /* * Setup a scan key to find chunks with matching va_valueid */ ScanKeyInit(&toastkey, (AttrNumber) 1, BTEqualStrategyNumber, F_OIDEQ, ObjectIdGetDatum(toast_pointer.va_valueid)); /* * Find all the chunks. (We don't actually care whether we see them in * sequence or not, but since we've already locked the index we might as * well use systable_beginscan_ordered.) */ toastscan = systable_beginscan_ordered(toastrel, toastidx, SnapshotToast, 1, &toastkey); while ((toasttup = systable_getnext_ordered(toastscan, ForwardScanDirection)) != NULL) { /* * Have a chunk, delete it */ simple_heap_delete(toastrel, &toasttup->t_self); } /* * End scan and close relations */ systable_endscan_ordered(toastscan); index_close(toastidx, RowExclusiveLock); heap_close(toastrel, RowExclusiveLock); } /* ---------- * toast_fetch_datum - * * Reconstruct an in memory Datum from the chunks saved * in the toast relation * ---------- */ static struct varlena * toast_fetch_datum(struct varlena * attr) { Relation toastrel; Relation toastidx; ScanKeyData toastkey; SysScanDesc toastscan; HeapTuple ttup; TupleDesc toasttupDesc; struct varlena *result; struct varatt_external toast_pointer; int32 ressize; int32 residx, nextidx; int32 numchunks; Pointer chunk; bool isnull; char *chunkdata; int32 chunksize; /* Must copy to access aligned fields */ VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr); ressize = toast_pointer.va_extsize; numchunks = ((ressize - 1) / TOAST_MAX_CHUNK_SIZE) + 1; result = (struct varlena *) palloc(ressize + VARHDRSZ); if (VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer)) SET_VARSIZE_COMPRESSED(result, ressize + VARHDRSZ); else SET_VARSIZE(result, ressize + VARHDRSZ); /* * Open the toast relation and its index */ toastrel = heap_open(toast_pointer.va_toastrelid, AccessShareLock); toasttupDesc = toastrel->rd_att; toastidx = index_open(toastrel->rd_rel->reltoastidxid, AccessShareLock); /* * Setup a scan key to fetch from the index by va_valueid */ ScanKeyInit(&toastkey, (AttrNumber) 1, BTEqualStrategyNumber, F_OIDEQ, ObjectIdGetDatum(toast_pointer.va_valueid)); /* * 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. */ nextidx = 0; toastscan = systable_beginscan_ordered(toastrel, toastidx, SnapshotToast, 1, &toastkey); while ((ttup = systable_getnext_ordered(toastscan, ForwardScanDirection)) != NULL) { /* * Have a chunk, extract the sequence number and the data */ residx = 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 (residx != nextidx) elog(ERROR, "unexpected chunk number %d (expected %d) for toast value %u in %s", residx, nextidx, toast_pointer.va_valueid, RelationGetRelationName(toastrel)); if (residx < numchunks - 1) { if (chunksize != TOAST_MAX_CHUNK_SIZE) elog(ERROR, "unexpected chunk size %d (expected %d) in chunk %d of %d for toast value %u in %s", chunksize, (int) TOAST_MAX_CHUNK_SIZE, residx, numchunks, toast_pointer.va_valueid, RelationGetRelationName(toastrel)); } else if (residx == numchunks - 1) { if ((residx * TOAST_MAX_CHUNK_SIZE + chunksize) != ressize) elog(ERROR, "unexpected chunk size %d (expected %d) in final chunk %d for toast value %u in %s", chunksize, (int) (ressize - residx * TOAST_MAX_CHUNK_SIZE), residx, toast_pointer.va_valueid, RelationGetRelationName(toastrel)); } else elog(ERROR, "unexpected chunk number %d (out of range %d..%d) for toast value %u in %s", residx, 0, numchunks - 1, toast_pointer.va_valueid, RelationGetRelationName(toastrel)); /* * Copy the data into proper place in our result */ memcpy(VARDATA(result) + residx * TOAST_MAX_CHUNK_SIZE, chunkdata, chunksize); nextidx++; } /* * Final checks that we successfully fetched the datum */ if (nextidx != numchunks) elog(ERROR, "missing chunk number %d for toast value %u in %s", nextidx, toast_pointer.va_valueid, RelationGetRelationName(toastrel)); /* * End scan and close relations */ systable_endscan_ordered(toastscan); index_close(toastidx, AccessShareLock); heap_close(toastrel, AccessShareLock); return result; } /* ---------- * toast_fetch_datum_slice - * * Reconstruct a segment of a Datum from the chunks saved * in the toast relation * ---------- */ static struct varlena * toast_fetch_datum_slice(struct varlena * attr, int32 sliceoffset, int32 length) { Relation toastrel; Relation toastidx; ScanKeyData toastkey[3]; int nscankeys; SysScanDesc toastscan; HeapTuple ttup; TupleDesc toasttupDesc; struct varlena *result; struct varatt_external toast_pointer; int32 attrsize; int32 residx; int32 nextidx; int numchunks; int startchunk; int endchunk; int32 startoffset; int32 endoffset; int totalchunks; Pointer chunk; bool isnull; char *chunkdata; int32 chunksize; int32 chcpystrt; int32 chcpyend; Assert(VARATT_IS_EXTERNAL(attr)); /* Must copy to access aligned fields */ VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr); /* * It's nonsense to fetch slices of a compressed datum -- this isn't lo_* * we can't return a compressed datum which is meaningful to toast later */ Assert(!VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer)); attrsize = toast_pointer.va_extsize; totalchunks = ((attrsize - 1) / TOAST_MAX_CHUNK_SIZE) + 1; if (sliceoffset >= attrsize) { sliceoffset = 0; length = 0; } if (((sliceoffset + length) > attrsize) || length < 0) length = attrsize - sliceoffset; result = (struct varlena *) palloc(length + VARHDRSZ); if (VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer)) SET_VARSIZE_COMPRESSED(result, length + VARHDRSZ); else SET_VARSIZE(result, length + VARHDRSZ); if (length == 0) return result; /* Can save a lot of work at this point! */ startchunk = sliceoffset / TOAST_MAX_CHUNK_SIZE; endchunk = (sliceoffset + length - 1) / TOAST_MAX_CHUNK_SIZE; numchunks = (endchunk - startchunk) + 1; startoffset = sliceoffset % TOAST_MAX_CHUNK_SIZE; endoffset = (sliceoffset + length - 1) % TOAST_MAX_CHUNK_SIZE; /* * Open the toast relation and its index */ toastrel = heap_open(toast_pointer.va_toastrelid, AccessShareLock); toasttupDesc = toastrel->rd_att; toastidx = index_open(toastrel->rd_rel->reltoastidxid, AccessShareLock); /* * 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)); /* * Use equality condition for one chunk, a range condition otherwise: */ if (numchunks == 1) { 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; } /* * Read the chunks by index * * The index is on (valueid, chunkidx) so they will come in order */ nextidx = startchunk; toastscan = systable_beginscan_ordered(toastrel, toastidx, SnapshotToast, nscankeys, toastkey); while ((ttup = systable_getnext_ordered(toastscan, ForwardScanDirection)) != NULL) { /* * Have a chunk, extract the sequence number and the data */ residx = 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 ((residx != nextidx) || (residx > endchunk) || (residx < startchunk)) elog(ERROR, "unexpected chunk number %d (expected %d) for toast value %u in %s", residx, nextidx, toast_pointer.va_valueid, RelationGetRelationName(toastrel)); if (residx < totalchunks - 1) { if (chunksize != TOAST_MAX_CHUNK_SIZE) elog(ERROR, "unexpected chunk size %d (expected %d) in chunk %d of %d for toast value %u in %s when fetching slice", chunksize, (int) TOAST_MAX_CHUNK_SIZE, residx, totalchunks, toast_pointer.va_valueid, RelationGetRelationName(toastrel)); } else if (residx == totalchunks - 1) { if ((residx * TOAST_MAX_CHUNK_SIZE + chunksize) != attrsize) elog(ERROR, "unexpected chunk size %d (expected %d) in final chunk %d for toast value %u in %s when fetching slice", chunksize, (int) (attrsize - residx * TOAST_MAX_CHUNK_SIZE), residx, toast_pointer.va_valueid, RelationGetRelationName(toastrel)); } else elog(ERROR, "unexpected chunk number %d (out of range %d..%d) for toast value %u in %s", residx, 0, totalchunks - 1, toast_pointer.va_valueid, RelationGetRelationName(toastrel)); /* * Copy the data into proper place in our result */ chcpystrt = 0; chcpyend = chunksize - 1; if (residx == startchunk) chcpystrt = startoffset; if (residx == endchunk) chcpyend = endoffset; memcpy(VARDATA(result) + (residx * TOAST_MAX_CHUNK_SIZE - sliceoffset) + chcpystrt, chunkdata + chcpystrt, (chcpyend - chcpystrt) + 1); nextidx++; } /* * Final checks that we successfully fetched the datum */ if (nextidx != (endchunk + 1)) elog(ERROR, "missing chunk number %d for toast value %u in %s", nextidx, toast_pointer.va_valueid, RelationGetRelationName(toastrel)); /* * End scan and close relations */ systable_endscan_ordered(toastscan); index_close(toastidx, AccessShareLock); heap_close(toastrel, AccessShareLock); return result; }