interface SqlQueryResponseIsTruncated reports that the query matched rows not included in Rows.
Rows holds at most the configured row limit (1000 by default), each ordered like Columns.
TruncationReason is "row_limit" when the query matched more rows than the row limit, "size_limit" when the rows past about 10 MB were left out, or null.
Warnings contains query planning warnings. Empty when there are no warnings.