Function GetLowerBoundForLessThan

pg_documentdb/src/opclass/bson_gin_core.c:4079–4179

* Given a bson type returns the lowest value for that type bracket * for the sort order type. */

 * for the sort order type.
 */
static bson_value_t
GetLowerBoundForLessThan(bson_type_t inputBsonType)
{
	bson_value_t minValue = { 0 };
	minValue.value_type = BSON_TYPE_MINKEY;
	switch (inputBsonType)
	{
		case BSON_TYPE_EOD:
		case BSON_TYPE_MINKEY:
		{
			/* The minValue for MinKey is MinKey */
			return minValue;
		}

		case BSON_TYPE_UNDEFINED:
		case BSON_TYPE_NULL:
		{
			/* Use MinKey here since null has custom semantics */
			return minValue;
		}

		case BSON_TYPE_DOUBLE:
		case BSON_TYPE_INT32:
		case BSON_TYPE_INT64:
		case BSON_TYPE_DECIMAL128:
		{
			minValue.value_type = BSON_TYPE_DOUBLE;
			minValue.value.v_double = NAN;
			return minValue;
		}

		case BSON_TYPE_UTF8:
		case BSON_TYPE_SYMBOL:
		{
			minValue.value_type = inputBsonType;
			minValue.value.v_utf8.len = 0;
			minValue.value.v_utf8.str = "";
			return minValue;
		}

		case BSON_TYPE_DOCUMENT:
		{
			/* Return an empty document */
			pgbson *bson = PgbsonInitEmpty();
			return ConvertPgbsonToBsonValue(bson);
		}

		case BSON_TYPE_ARRAY:
		{
			pgbson_writer bsonWriter;

			/* now create a bson for that path which has the min value for the field */
			/* we map this to an empty array since that's the smallest value we'll encounter */
			PgbsonWriterInit(&bsonWriter);
			PgbsonWriterAppendEmptyArray(&bsonWriter, "", 0);
			pgbson *doc = PgbsonWriterGetPgbson(&bsonWriter);

			pgbsonelement termElement;