Function svec_pivot

methods/svec_util/src/pg_gp/svec_util.c:709–813

* Aggregate function svec_pivot takes its float8 argument and appends it * to the state variable (an svec) to produce the concatenated return variable. * The StringInfo variables within the state variable svec are used in a way * that minimizes the number of memory re-allocations. * * Note that the first time this is called, the state variable should be null. */

 * Note that the first time this is called, the state variable should be null.
 */
Datum svec_pivot(PG_FUNCTION_ARGS)
{
	SvecType *svec;
	SparseData sdata;
	float8 value;

	if (PG_ARGISNULL(1)) value = NVP;
	else value = PG_GETARG_FLOAT8(1);

	if (! PG_ARGISNULL(0))
	{
		svec = PG_GETARG_SVECTYPE_P_COPY(0);
	} else {	//first call, construct a new svec
		/*
		 * Allocate space for the unique values and index
		 *
		 * Note that we do this manually because we are going to
		 * manage the memory allocations for the StringInfo structures
		 * manually within this aggregate so that we can preserve
		 * the intermediate state without re-serializing until there is
		 * a need to re-alloc, at which point we will re-serialize to
		 * form the returned state variable.
		 */
		svec = makeEmptySvec(1);
	}
	sdata = sdata_from_svec(svec);

	/*
	 * Add the incoming float8 value to the svec.
	 *
	 * First check to see if there is room in both the data area and index
	 * and if there isn't, re-alloc and recreate the svec
	 */
	if (   ((Size) (sdata->vals->len + sizeof(float8)+1) > (Size) sdata->vals->maxlen)
	    || ((Size) (sdata->index->len + 9 +1)            > (Size) sdata->index->maxlen) )
	{
		svec = reallocSvec(svec);
		sdata = sdata_from_svec(svec);
	}

	/*
	 * Now let's check to see if we're adding a new value or appending to
	 * the last run.  If the incoming value is the same as the last value,
	 * just increment the last run.  Note that we need to use the index
	 * cursor to find where the last index counter is located.
	 */
	{
		char *index_location;
		int old_index_storage_size;
		int64 run_count;
		float8 last_value=-100000;
		bool new_run;

		if (sdata->index->len==0) //New vector
		{
			new_run=true;
			index_location = sdata->index->data;
			sdata->index->cursor = 0;