On Jul 11, 2015 6:19 PM, "Pavel Stehule" <pavel.stehule@gmail.com> wrote: > > > > 2015-07-11 18:02 GMT+02:00 Shulgin, Oleksandr <oleksandr.shulgin@zalando.de>: >> >> On Fri, Jul 10, 2015 at 5:16 PM, Pavel Stehule <pavel.stehule@gmail.com> wrote: >>>> >>>> >>>> Well, one could call it premature pessimization due to dynamic call overhead. >>>> >>>> IMO, the fact that json_out_init_context() sets the value callback to json_out_value is an implementation detail, the other parts of code should not rely on. And for the Explain output, there definitely going to be *some* code between context initialization and output callbacks: these are done in a number of different functions. >>> >>> >>> Again - it is necessary? Postgres still use modular code, not OOP code. I can understand the using of this technique, when I need a possibility to change behave. But these function are used for printing JSON, not printing any others. >> >> >> No, it's not strictly necessary. >> >> For me it's not about procedural- vs. object- style, but rather about being able to override/extend the behavior consistently. And for that I would prefer that if I override the value callback in a JSON output context, that it would be called for every value being printed, not only for some of them. > > > please, can me show any real use case? JSON is JSON, not art work.
To quote my first mail:
The motivation behind this to be able to produce specially-crafted JSON in a logical replication output plugin, such that numeric (and bigint) values are quoted. This requirement, in turn, arises from the fact that JavaScript specification, which is quite natural to expect as a consumer for this JSON data, allows to silently drop significant digits when converting from string to number object.
I believe this is a well-known problem and I'm aware of a number of tricks that might be used to avoid it, but none of them seems to be optimal from my standpoint.
I can also imagine this can be used to convert date/time to string differently, or adding indentation depending on the depth in object hierarchy, etc.
There is simple rule - be strict on output and tolerant on input. If I understand to sense of this patch - the target is one same format of JSON documents - so there are no space for any variability.
> Still I don't see any value of this.
Huh? Why then do you spend time on review?
I am thinking so general json functions has sense, but I partially disagree with your implementation.