Parse json arrays using HIVE - arrays

Question

I have many json arrays stored in a table (jt) that looks like this:
[{"ts":1403781896,"id":14,"log":"show"},{"ts":1403781896,"id":14,"log":"start"}]
[{"ts":1403781911,"id":14,"log":"press"},{"ts":1403781911,"id":14,"log":"press"}]
Each array is a record.
I would like to parse this table in order to get a new table (logs) with 3 fields: ts, id, log.
I tried to use the get_json_object method, but it seems that method is not compatible with json arrays because I only get null values.
This is the code I have tested:
CREATE TABLE logs AS
SELECT get_json_object(jt.value, '$.ts') AS ts,
get_json_object(jt.value, '$.id') AS id,
get_json_object(jt.value, '$.log') AS log
FROM jt;
I tried to use other functions but they seem really complicated.
Thank you! :)
Update!
I solved my issue by performing a regexp:
CREATE TABLE jt_reg AS
select regexp_replace(regexp_replace(value,'\\}\\,\\{','\\}\\\n\\{'),'\\[|\\]','') as valuereg from jt;
CREATE TABLE logs AS
SELECT get_json_object(jt_reg.valuereg, '$.ts') AS ts,
get_json_object(jt_reg.valuereg, '$.id') AS id,
get_json_object(jt_reg.valuereg, '$.log') AS log
FROM ams_json_reg;

Answer 1

I just ran into this problem, with the JSON array stored as a string in the hive table.
The solution is a bit hacky and ugly, but it works and doesn't require serdes or external UDFs
SELECT
get_json_object(single_json_table.single_json, '$.ts') AS ts,
get_json_object(single_json_table.single_json, '$.id') AS id,
get_json_object(single_json_table.single_json, '$.log') AS log
FROM ( SELECT explode (
split(regexp_replace(substr(json_array_col, 2, length(json_array_col)-2),
'"}","', '"}",,,,"'), ',,,,')
) FROM src_table) single_json_table;
I broke the lines up so that it would be a little easier to read.
I'm using substr() to strip the first and last characters, removing [ and ] . I'm then using regex_replace to match the separator between records in the json array and adding or changing the separator to be something unique that can then be used easily with split() to turn the string into a hive array of json objects which can then be used with explode() as described in the previous solution.
Note, the separator regex used here ( "}"," ) wouldn't work with the original data set...the regex would have to be ( "},\{" ) and the replacement would then need to be "},,,,{" eg..
split(regexp_replace(substr(json_array_col, 2, length(json_array_col)-2),
'"},\\{"', '"},,,,{"'), ',,,,')

Answer 2

Use explode() function
hive (default)> CREATE TABLE logs AS
> SELECT get_json_object(single_json_table.single_json, '$.ts') AS ts,
> get_json_object(single_json_table.single_json, '$.id') AS id,
> get_json_object(single_json_table.single_json, '$.log') AS log
> FROM
> (SELECT explode(json_array_col) as single_json FROM jt) single_json_table ;
Automatically selecting local only mode for query
Total MapReduce jobs = 3
Launching Job 1 out of 3
Number of reduce tasks is set to 0 since there's no reduce operator
hive (default)> select * from logs;
OK
ts id log
1403781896 14 show
1403781896 14 start
1403781911 14 press
1403781911 14 press
Time taken: 0.118 seconds, Fetched: 4 row(s)
hive (default)>
where json_array_col is column in jt which holds your array of jsons.
hive (default)> select json_array_col from jt;
json_array_col
["{"ts":1403781896,"id":14,"log":"show"}","{"ts":1403781896,"id":14,"log":"start"}"]
["{"ts":1403781911,"id":14,"log":"press"}","{"ts":1403781911,"id":14,"log":"press"}"]

Answer 3

because get_json_object doesn't support json array string, so you can concat to a json object, like this:
SELECT
get_json_object(concat(concat('{"root":', jt.value), '}'), '$.root')
FROM jt;