Function TruncateNestedEntry

pg_documentdb/src/opclass/gin_index_term.c:1385–1555

* Truncate an entry that is present in an object or array. * For types that don't support truncation mark the outer entry as definitely * not truncated. */

 * not truncated.
 */
static bool
TruncateNestedEntry(pgbson_element_writer *elementWriter, const
					bson_value_t *currentValue,
					bool *forceAsNotTruncated, int32_t sizeBudgetForElementWriter, int32_t
					currentLength)
{
	switch (currentValue->value_type)
	{
		/* Fixed size values - just write it out */
		case BSON_TYPE_MAXKEY:
		case BSON_TYPE_MINKEY:
		case BSON_TYPE_BOOL:
		case BSON_TYPE_DATE_TIME:
		case BSON_TYPE_NULL:
		case BSON_TYPE_OID:
		case BSON_TYPE_TIMESTAMP:
		case BSON_TYPE_UNDEFINED:
		{
			/* Primitive values aren't truncated */
			PgbsonElementWriterWriteValue(elementWriter, currentValue);
			return false;
		}

		case BSON_TYPE_DECIMAL128:
		case BSON_TYPE_DOUBLE:
		case BSON_TYPE_INT32:
		case BSON_TYPE_INT64:
		{
			/* These are variable length but can be compared together
			 * To ensure we have proper comparison in the middle of an array,
			 * Convert them to a unified type. This is needed to handle
			 * terms that come after the number.
			 * e.g. if you had an array
			 * [ Int32(1), "123456789012345" ]
			 * and
			 * [ Decimal128(1), "123456789012345" ]
			 *
			 * These 2 arrays are and should be able to be read via a query of
			 * $eq: [ Double(1), "1234567890123456789" ]
			 *
			 * If the truncation limit was say 18 bytes we would get
			 * (ignoring structural overhead):
			 * [ Int32(1), "123456789012345"] (not truncated)
			 * [ Decimal128(1), "12" ] (truncated)
			 * which can produce incorrect results.
			 *
			 * So we convert all numerics to a common value.
			 */
			bson_value_t numericValue = *currentValue;
			bool checkFixedInteger = true;
			if (IsBsonValue32BitInteger(currentValue, checkFixedInteger))
			{
				numericValue.value.v_int32 = BsonValueAsInt32(currentValue);
				numericValue.value_type = BSON_TYPE_INT32;
			}
			else if (IsBsonValue64BitInteger(currentValue, checkFixedInteger))
			{
				numericValue.value.v_int64 = BsonValueAsInt64(currentValue);