Not out of the box. Fields are parsed into tokens and queries search on tokens. An empty string has no tokens for that field and a missing field has no tokens for that field.
If you really need to do this, then you’ll need to turn the empty string in a special token that means “empty string”, choosing a token that won’t conflict with any real token. At this point, we’re moving into Ugly Hack Land, but sometimes that is the best we can do. For example, you could create an update request processor that checked for a field with an empty value, then replaced that with a rare character, perhaps a composed, compatibility Unicode character, like Angstrom (same as circle capital A), or one of the TV Guide symbols (numbers in TV-shaped surrounds), or my personal favorite, the IPA symbol for “audible gnashing of teeth”, which could be an appropriate response to this request. That character is U+02AD, "LATIN LETTER BIDENTAL PERCUSSIVE” (http://www.fileformat.info/info/unicode/char/2ad/index.htm). Then you would need to craft a query using this special token to mean “empty string”. Of course, none of this works if some upstream processing of the update document strips fields with empty values. wunder Walter Underwood wun...@wunderwood.org http://observer.wunderwood.org/ (my blog) On May 18, 2015, at 5:56 PM, Shawn Heisey <apa...@elyograg.org> wrote: > Can I search for the empty string? This is distinct from searching for > documents that don't have a certain fieldat all, which I can already do > with a clause of "*:* -field:[*TO *]"in my query. > > Thanks, > Shawn >
