示例#1
0
文件: tuptoaster.c 项目: nskyzh/gpdb
/* ----------
 * 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);
	}
}
示例#2
0
/*
 * 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;
}