Unable to decompose nested JSON in Spark dataframe

Question content

I am new to spark. I'm trying to flatten the dataframe but am not able to do it via "explode".

The original data frame structure is as follows:

id|approvaljson
1|[{"approvertype":"1st line manager","status":"approved"},{"approvertype":"2nd line manager","status":"approved"}]
2|[{"approvertype":"1st line manager","status":"approved"},{"approvertype":"2nd line manager","status":"rejected"}]

Do I need to convert it to the following schema?

id|approvaltype|status
1|1st line manager|approved
1|2nd line manager|approved
2|1st line manager|approved
2|2nd line manager|rejected

I've tried it

df_exploded = df.withcolumn("approvaljson", explode("approvaljson"))

But I got the error:

Cannot resolve "explode(ApprovalJSON)" due to data type mismatch:
parameter 1 requires ("ARRAY" or "MAP") type, however, "ApprovalJSON"
is of "STRING" type.;

Correct answer

First parse the json-like string into an array of structures, then use inline to break the array into rows and columns

df1 = df.withcolumn("approvaljson", f.from_json("approvaljson", schema="array<struct<approvertype string, status string>>"))
df1 = df1.select("id", f.inline('approvaljson'))

result

df1.show()

+---+----------------+--------+
| ID|    ApproverType|  Status|
+---+----------------+--------+
|  1|1st Line Manager|Approved|
|  1|2nd Line Manager|Approved|
|  2|1st Line Manager|Approved|
|  2|2nd Line Manager|Rejected|
+---+----------------+--------+

The above is the detailed content of Unable to decompose nested JSON in Spark dataframe. For more information, please follow other related articles on the PHP Chinese website!