Hi all, If you are familiar with the tree model, you should know that for a device d1, if it contains three sensors: s1, s2, s3, and its data are like: Time | s1 | s2 | s3 | -------|-----|-----|-----| 1 | 1| 10|100 | -------|-----|-----|-----| 2 | 2| null|null | -------|-----|-----|-----| 3 | 3| null|null |
if we only query s2 and s3, select s2, s3 from root.db.d1, we will only get one row(the first row), because for 2 and 3 row, s2 and s3 are all null, we automatically filter out rows that are entirely null during a scan by the storage engine. However, this is inconsistent with the behavior of relational databases which will return all three rows. So in our table model, should we keep consistent with tree model, or we follow the relational databases way? Personally, I think that we should maintain consistency with relational databases. What do you think? Best regards, ---------------------- Yuan Tian
