Re: BUG #13996: json_to_record() returns non-NULL, malformed value for omitted key under some circumstances

On 03/02/2016 08:04 PM, Tom Lane wrote:
> johann(at)visagie(dot)za(dot)net writes:
>> SELECT t.*
>> FROM json_to_record('{"a":1, "b":{"c":16, "d":2}, "x":8}'::json)
>> AS t(a int, b json, c text, x int);
>> However, if (as in this example) another key in the JSON object - `b` in
>> this case - refers to a nested JSON object which *does* contain a key `c`,
>> the function returns a malformed JSON string as (text) value for column
>> `c`:
>> a | b | c | x
>> ---+----------------+---------+---
>> 1 | {"c":16,"d":2} | {"c":16 | 8
>> (1 row)
>
> AFAICT this is a simple thinko in the hash_object_field_end() callback,
> as per attached patch that fixes this and doesn't break any existing
> regression test cases. Andrew, do you concur that this is correct,
> or is there something I'm missing about the tracking of lex_level?
>
>

Looks like you're right. lex_level is incremented at object/array start
and decremented at object/array end. So keys of the outermost object
will be at lex_level 1, and we shouldn't be using anything at a higher
level. I guess we should add something like this as an extra regression
test.

cheers

andrew