Apologies for the miscommunication. I meant to say that keeping all-null rows
will be better for the table model.
> From: "Stefanie Zhao"<zhaoxi...@apache.org>
> Date: Fri, Aug 30, 2024, 15:16
> Subject: Re: Whether to automatically filter out rows that are entirely null
> in the result set during a scan by the storage engine
> To: <dev@iotdb.apache.org>
> I think for table model, filter out all-null rows will be better. User can
> use "is not null" statement to filter all-null rows if they want (though a
> little bit inconvenient to use when there are many columns). And for the tree
> model, keep the current define is better.
>
> On 2024/08/29 01:45:07 Yuan Tian wrote:
> > 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
> >
