If you call removeField(name) from a BaseDBObject and then call toString(), the fields are still there and only the value is null. I would expect that it would remove all filed and the value.

E.g.

if (site.containsKey(SiteDocField.HOMEPAGE_CRAWL_CONTENT.key))

{ site.removeField(SiteDocField.HOMEPAGE_CRAWL_CONTENT.key); }

The JSON below still contains homec/HOMEPAGE_CRAWL_CONTENT.key

{"site":

{"blc":1104883,"tldid":1,"homefu":"http://www.bloomberg.com/","homec":null,"h":"www.bloomberg.com","homert":2072,"_ns":"sites","lhomet":1249578595914,"idxc":1104883,"_id":null,"hsyndf":false,"ta":1249578575882,"lfext":1249578615980,"lidxt":1249578595914,"hcopy":false,"lgpr":1249578595914,"lblct":1249578595914,"homerc":200}

,"siteId":"8c779c4797f10c5a1287c0e89cec4ae7"}