Oracle 12c JSON TABLE解析错误处理

Question

Is it possible to handle error while parsing invalid JSON with JSON_TABLE ? Like for example below query works

SELECT *
FROM 
JSON_TABLE(
    '[{"productCode":"AD","serials":[{"id":"234242343","isPrimary":true}]},{"productCode":"BC","serials":[{"id":"23345345","isPrimary":true}]}]'
    , '$[*]'
    columns(
        productCode varchar2 PATH '$.productCode' NULL ON ERROR,
        serials varchar2 format JSON PATH '$.serials' NULL ON ERROR
    )
);

The output for above is as below:

|PRODUCTCODE | SERIALS                              |
|---------------------------------------------------|
|AD          |[{"id":"234242343","isPrimary":true}] |
|BC          |[{"id":"23345345","isPrimary":true}]  |

Here in the above example, the input JSON is valid, however, in my case, there is no guarantee as its being fetched from another log table.

I want the query to ignore if it encounters invalid JSON.

Answer 1

The easy way is transferring your data into new table with check constraint in order to check whether the data in the source table conforms to JSON format as being an Oracle 12c+ user.

If the format is false, then the row won't be inserted into that new table such as

CREATE TABLE tab_new (
  id      INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
  jsdata  VARCHAR2(500),
  CONSTRAINT json_chk CHECK (jsdata IS JSON)
);

BEGIN
  FOR C IN ( SELECT jsdata FROM tab_old )
  LOOP
  BEGIN
     INSERT INTO tab_new(jsdata) VALUES(c.jsdata) ;
   EXCEPTION
     WHEN OTHERS THEN IF SQLCODE = -2290 THEN 
                       INSERT INTO tab_error(jsdata) VALUES(c.jsdata) ;
                      END IF;
  END;
  END LOOP;
  COMMIT;
END;
/

Demo

Answer 2

You can use the is json condition to filter out invalid JSON:

create table t (
  what varchar2(20),
  c1   varchar2(500)
);

insert into t 
  values ( 'valid JSON', '[{"productCode":"AD","serials":[{"id":"234242343","isPrimary":true}]},{"productCode":"BC","serials":[{"id":"23345345","isPrimary":true}]}]' );
insert into t 
  values ( 'invalid JSON', '"productCode":"AD","serials":[{"id":"234242343","isPrimary":true}]},{"productCode":"BC","serials":[{"id":"23345345","isPrimary":true}]}]' );
commit;

select what from t
where  c1 is json;

WHAT         
valid JSON   

But this is unnecessary: json_table already ignores invalid documents!

SELECT what, j.*
FROM   t, JSON_TABLE(
    c1, '$[*]'
    columns(
      productCode varchar2 PATH '$.productCode' NULL ON ERROR,
      serials varchar2 format JSON PATH '$.serials' NULL ON ERROR
    )
) j;

WHAT          PRODUCTCODE    SERIALS                                 
valid JSON    AD             [{"id":"234242343","isPrimary":true}]    
valid JSON    BC             [{"id":"23345345","isPrimary":true}]  

You can force an error on invalid JSON with the on error clause:

SELECT what, j.*
FROM   t, JSON_TABLE(
    c1, '$[*]'
    error on error
    columns (
      productCode varchar2 PATH '$.productCode' NULL ON ERROR,
      serials varchar2 format JSON PATH '$.serials' NULL ON ERROR
    )
) j;

ORA-40441: JSON syntax error