Allow searching for null values

[JasonSanford]

I had a hard time searching for null values in a TileMill project earlier.

I tried

[field is null]

[field=null]

[field='null']

[field='']

without any luck.

[springmeyer]

@JasonSanford - thanks for reporting. So [field=""] works for me with geojson datasource. What datasource were you testing with and finding no easy solution?

[JasonSanford]

Oh yeah, I should have added that. I'm using a PostGIS datasource.

[springmeyer]

Okay, had a chance to look into this. It is due to some unfinished work in the mapnik PostGIS datasource driver. The fix is quite simple and easy, but I'll need to make sure there are no unintended consequences. http://trac.mapnik.org/ticket/794

My understanding from twitter is that you found a workaround for this issue and its not pressing - so I'm going to close as the issue can now be tracked upstream at http://trac.mapnik.org/ticket/794. I doubt anything in carto would affect this.

closing.

[springmeyer]

re-opening. Realizing I closed this saying I would deal with it on the mapnik side, and never ended up doing so. Needs another look (and a clean, small testcase).

[tmcw]

[field=null] is now supported. is is not a valid operator.

[springmeyer]

also, mapnik/mapnik#1644 is now done for postgres, meaning my comment that triggered re-opening is not fully settled. Things should be (and have been) working fine and tests now conclusively show that.