jq --stream filter on multiple values of same key

Question

I am processing a very large JSON wherein I need to filter the inner JSON objects using a value of a key. My JSON looks like as follows:

{"userActivities":{"L3ATRosRdbDgSmX75Z":{"deviceId":"60ee32c2fae8dcf0","dow":"Friday","localDate":"2018-01-20"},"L3ATSFGrpAYRkIIKqrh":{"deviceId":"60ee32c2fae8dcf0","dow":"Friday","localDate":"2018-01-21"},"L3AVHvmReBBPNGluvHl":{"deviceId":"60ee32c2fae8dcf0","dow":"Friday","localDate":"2018-01-22"},"L3AVIcqaDpZxLf6ispK":{"deviceId":"60ee32c2fae8dcf0","dow":"Friday,"localDate":"2018-01-19"}}}

I want to put a filter on localDate values such that localDate in 2018-01-20 or localDate in "2018-01-21" such that the output look like.

{"userActivities":{"L3ATRosRdbDgSmX75Z":{"deviceId":"60ee32c2fae8dcf0","dow":"Friday","localDate":"2018-01-20"},"L3ATSFGrpAYRkIIKqrh":{"deviceId":"60ee32c2fae8dcf0","dow":"Friday","localDate":"2018-01-21"}}}

I have asked a similar question here and realised that I need to put filter on multiple values and retain the original structure of JSON.

https://stackoverflow.com/questions/52324497/how-to-filter-json-using-jq-stream

Thanks a ton in advance!

Answer 1

From the jq Cookbook, let's borrow def atomize(s):

# Convert an object (presented in streaming form as the stream s) into
# a stream of single-key objects
# Examples:
#   atomize({a:1,b:2}|tostream)
#   atomize(inputs) (used in conjunction with "jq -n --stream")
def atomize(s):
  fromstream(foreach s as $in ( {previous:null, emit: null};
      if ($in | length == 2) and ($in|.[0][0]) != .previous and .previous != null
      then {emit: [[.previous]], previous: $in|.[0][0]}
      else { previous: ($in|.[0][0]), emit: null}
      end;
      (.emit // empty), $in) ) ;

Since the top-level object described by the OP contains just one key, we can select the August 2018 objects as follows:

atomize(1|truncate_stream(inputs))
| select( .[].localDate[0:7] == "2018-08")

If you want these collected into a composite object, you might have to be careful about memory, so you might want to pipe the selected objects to another program (e.g. awk or jq). Otherwise, I'd go with:

def add(s): reduce s as $x (null; .+$x);

{"userActivities": add(
    atomize(1|truncate_stream(inputs | select(.[0][0] == "userActivities")))
    | select( .[].localDate[0:7] =="2018-01") ) }

Variation

If the top-level object has more than one key, then the following variation would be appropriate:

atomize(1|truncate_stream(inputs | select(.[0][0] == "userActivities")))
| select( .[].localDate[0:7] =="2018-08")