Function FillWeightsSpec

pg_documentdb/src/opclass/bson_text_gin.c:1080–1203

* Populates the index option weights into the index spec * This includes the path and associated weights encoded as follows * [ ]+ */

 * <numPaths><Datum[4] of weights>[<pathLength><path><weightIndex>]+
 */
static Size
FillWeightsSpec(const char *weightsSpec, void *buffer)
{
	/* Weights count + Weight array (for rank) */
	Size sizeRequired = sizeof(uint32_t) + (sizeof(Datum) * 4);

	pgbson *bson;
	if (weightsSpec != NULL && strlen(weightsSpec) > 0)
	{
		bson = PgbsonInitFromJson(weightsSpec);
	}
	else
	{
		bson = PgbsonInitEmpty();
	}

	bson_iter_t weightsIter;
	PgbsonInitIterator(bson, &weightsIter);

	int pathCount = 0;
	float4 maxWeight = 0;
	while (bson_iter_next(&weightsIter))
	{
		pathCount++;

		StringView pathView = bson_iter_key_string_view(&weightsIter);
		if (pathView.length == 0)
		{
			ereport(ERROR, (errcode(ERRCODE_DOCUMENTDB_BADVALUE), errmsg(
								"filter must have a valid path")));
		}

		/* add the prefixed path length */
		sizeRequired += sizeof(uint32_t);

		/* add the path size */
		sizeRequired += pathView.length;

		/* Add 1 character for 'weight' char (A, B, C, D)*/
		sizeRequired++;

		float4 weight = (float4) BsonValueAsDouble(bson_iter_value(&weightsIter));
		maxWeight = Max(weight, maxWeight);
	}

	maxWeight = Max(maxWeight, 1.0);
	if (buffer != NULL)
	{
		char *bufferPtr = (char *) buffer;

		/* Use memcpy to avoid misaligned memory access - buffer may not be 4-byte aligned */
		memcpy(bufferPtr, &pathCount, sizeof(uint32_t));
		bufferPtr += sizeof(uint32_t);

		/* Save space for the weights array */
		Datum *weightDatums = (Datum *) bufferPtr;
		bufferPtr += (sizeof(Datum) * 4);