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sql_maps.md

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Working with SQL Maps

Spark makes available a number of functions that operate on SQL maps. Geni makes all these functions available in the core namespace. On top of that, Geni also adds a number of synonyms from Clojure core's map functions.

The examples assume the following required namespaces:

(require '[zero-one.geni.core :as g])
(require '[zero-one.geni.ml :as ml])
(require '[zero-one.geni.test-resources :refer [melbourne-df]])

Creating Map Columns

We can create map types using map, map-from-entries and map-from-arrays as follows:

Note that melbourne-df is a function so we need to add () to evaluate it.

(def dataframe
  (-> (melbourne-df)
      (g/limit 2)
      (g/select
        {:location (g/map (g/lit "suburb") :Suburb
                          (g/lit "region") :Regionname
                          (g/lit "council") :CouncilArea
                          (g/lit "address") :Address)
         :market   (g/map-from-entries
                     (g/array (g/struct (g/lit "size") (g/double :Price))
                              (g/struct (g/lit "price") (g/double :Price))))
         :coord    (g/map-from-arrays
                     (g/array (g/lit "lat") (g/lit "long"))
                     (g/array :Lattitude :Longtitude))})))

(g/collect dataframe)
; =>
({:location
  {"suburb" "Abbotsford",
   "region" "Northern Metropolitan",
   "council" "Yarra",
   "address" "85 Turner St"},
  :market {"size" 1480000.0, "price" 1480000.0},
  :coord {"lat" -37.7996, "long" 144.9984}}
 {:location
  {"suburb" "Abbotsford",
   "region" "Northern Metropolitan",
   "council" "Yarra",
   "address" "25 Bloomburg St"},
  :market {"size" 1035000.0, "price" 1035000.0},
  :coord {"lat" -37.8079, "long" 144.9934}}]

SQL Map Functions and Synonyms

Note that map-from-arrays above is actually the same as Clojure's zipmap, and it would be more natural to use the latter in a Clojure codebase. For that reason, Geni includes the following functions:

Geni Original Spark
assoc -
dissoc -
keys map-keys
merge-with map-zip-with
merge map-concat
rename-keys -
select-keys -
update -
vals map-values
zipmap map-from-arrays