All of my records have a field called “pictures”. This field is an array of strings.
I now want the newest 10 records where this array IS NOT empty.
I’ve googled around, but strangely enough I haven’t found much on this.
I’ve read into the $where option, but I was wondering how slow that is to native functions, and if there is a better solution.
And even then, that does not work:
ME.find({$where: 'this.pictures.length > 0'}).sort('-created').limit(10).execFind()
Returns nothing. Leaving this.pictures without the length bit does work, but then it also returns empty records, of course.
If you also have documents that don’t have the key, you can use:
ME.find({ pictures: { $exists: true, $not: {$size: 0} } })
MongoDB doesn’t use indexes if $size is involved, so here is a better solution:
ME.find({ pictures: { $exists: true, $ne: [] } })
If your property can have invalid values (like null boolean or others) , then you an add an additional check using $types as proposed in this answer:
With mongo >= 3.2:
ME.find({ pictures: { $exists: true, $type: 'array', $ne: [] } })
With mongo < 3.2:
ME.find({ pictures: { $exists: true, $type: 4, $ne: [] } })
Since the MongoDB 2.6 release, you can compare with the operator $gt, but this could lead to unexpected results (you can find a detailed explanation in this answer):
ME.find({ pictures: { $gt: [] } })
