Confusing quick filter behavior around string column "null"

[devinrsmith]

I'm unable to do a literal search for the string "null" using the string "null" in the web UI quick filter - it assumes I want to search for the null value. This is due to an implementation detail in io.deephaven.engine.table.impl.select.MatchFilter when using MatchFilter#strValues:

Object convertStringLiteral(String str) {
    if (str.equals("null")) {
        return null;
    }
    ...
}

It may be that this is "as-desired", but it's a potential gotcha as it's different than every other string.

I see the importance of wanting to filter to null values, but I wonder if there might be a better way to expose this functionality? I wonder if an explicit option "is null" would be better? (This could also be a good place to introduce an "is empty" filter.)

I'm able to workaround this issue by going to advanced filters and explicitly selecting the "null" value.

As another note, the values in the advanced filters box might want to use the text rendering that the grid cell uses, so the user can tell the difference between null and "".

[devinrsmith]

Don noted a workaround, using the literal \null or =null, which seems to correctly search for the string "null". \ also works for literal empty (but = does not).

[dsmmcken]

typing = errors as invalid, but selecting context menu "filter by value" on empty fills the quick filter bar with just = as value and does work. So we should probably make that consistent.

[dsmmcken]

From slack:

Bender

Maybe we should have some sort of visual indicator when you enter null that it's searching for null instead of "null"? I dunno how we show that though

donmckenzie

yeah, present it similar to how it is in the table with italics?