Re: [PATCH] Generalized JSON output functions

On Jul 11, 2015 6:19 PM, "Pavel Stehule" <pavel.stehule@gmail.com> wrote:
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> 2015-07-11 18:02 GMT+02:00 Shulgin, Oleksandr <oleksandr.shulgin@zalando.de>:
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>> On Fri, Jul 10, 2015 at 5:16 PM, Pavel Stehule <pavel.stehule@gmail.com> wrote:
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>>>> Well, one could call it premature pessimization due to dynamic call overhead.
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>>>> 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.
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>>> 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.
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>> No, it's not strictly necessary.
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>> 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.
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> 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.

> Still I don't see any value of this.

Huh? Why then do you spend time on review?