/* ----------
* 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)
{
varattrib *tmp;
int32 valsize = VARSIZE_ANY_EXHDR_D(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 = (varattrib *) palloc(PGLZ_MAX_OUTPUT(valsize));
if (pglz_compress(VARDATA_ANY_D(value), valsize,
(PGLZ_Header *) tmp, PGLZ_strategy_default) &&
VARSIZE(tmp) < VARSIZE_ANY_D(value))
{
/* successful compression */
VARATT_SET_COMPRESSED(tmp);
return PointerGetDatum(tmp);
}
else
{
/* incompressible data */
pfree(tmp);
return PointerGetDatum(NULL);
}
}
/*
* heap_compute_data_size
* Determine size of the data area of a tuple to be constructed
*/
Size
heap_compute_data_size(TupleDesc tupleDesc,
Datum *values,
bool *isnull)
{
Size data_length = 0;
int i;
int numberOfAttributes = tupleDesc->natts;
Form_pg_attribute *att = tupleDesc->attrs;
for (i = 0; i < numberOfAttributes; i++)
{
if (isnull[i])
continue;
/* we're anticipating converting to a short varlena header even if it's
* not currently */
if (att[i]->attlen == -1 && value_type_could_short(values[i], att[i]->atttypid))
{
/* no alignment and we will convert to 1-byte header */;
data_length += VARSIZE_ANY_EXHDR_D(values[i]) + VARHDRSZ_SHORT;
}
else
{
data_length = att_align(data_length, att[i]->attalign);
data_length = att_addlength(data_length, att[i]->attlen, values[i]);
}
}
return data_length;
}