Question

I have a mongodb document with below structure..

{

    "key4" : 

         [
           {"k1":"v1", "k2":"va1", "k3":"value1"},         
           {"k1":"v2", "k2":"va2", "k4":"name"},
           {"k1":"v3", "k2":"va3"}
         ]
}

when i was updating this document with given structure..

{

    "key4" : 

         [
           {"k1":"v1", "k3":"val1"},         
           {"k1":"v2", "k3":"val2"},
           {"k1":"v3", "k3":"val3"},
           {"k1":"v4", "k3":"val4"}
         ]
}

i need output as..

{

"key4" : 

         [
           {"k1":"v1", "k2":"va1", "k3":"val1"},         
           {"k1":"v2", "k2":"va2", "k3":"val2", "k4":"name"},
           {"k1":"v3", "k2":"va3", "k3":"val3"},
           {"k1":"v4", "k3":"val4"}
         ]
}

which means that if value of ‘k1’ exist in the new array, it should merge the only object of array into new.
i am implementing this structure in clojure map.

Answer 1

you can get very close with a combination of merge-with, map, and merge

user> a
{"key4" [{"k1" "v1", "k2" "va1", "k3" "value1"} 
         {"k1" "v2", "k2" "va2", "k4" "name"} 
         {"k1" "v3", "k2" "va3"}]}
user> b
{"key4" [{"k1" "v1", "k3" "val1"} 
         {"k1" "v2", "k3" "val2"} 
         {"k1" "v3", "k3" "val3"} 
         {"k1" "v4", "k3" "val4"}]}
user> (merge-with #(map merge %1 %2) a b)
{"key4" 
    ({"k1" "v1", "k2" "va1", "k3" "val1"} 
     {"k1" "v2", "k2" "va2", "k3" "val2", "k4" "name"} 
     {"k1" "v3", "k2" "va3", "k3" "val3"})}
user> 

then you need to merge in any items from the longer set.