postgresql jsonpath support-CodePudding

I am running postgresql 12 and am trying to use jsonpath.

I'd like to use jsonb_path_query_first to get the length of an array. I know I can do json_array_length but would rather not.

Here is the query that I am trying to make work.

select jsonb_path_query_first('{"a":3,"b":6,"s":[1,2,3,4,5], "d":{"v":4}}'::jsonb, '$.s.length()'::jsonpath);
ERROR:  syntax error, unexpected '(', expecting end of file at or near "(" of jsonpath input
LINE 1: ...a":3,"b":6,"s":[1,2,3,4,5], "d":{"v":4}}'::jsonb, '$.s.lengt...

Does the version of jsonpath in postgresql 12 not support this type of jsonpath functionality.

CodePudding user response：

You can use the .size() method for this:

test# select 
          jsonb_path_query_first(
            '{"a":3,"b":6,"s":[1,2,3,4,5], "d":{"v":4}}'::jsonb,    
            '$.s.size()'::jsonpath
);

 jsonb_path_query_first 
════════════════════════
 5
(1 row)