On 09/14/2015 03:42 PM, Teodor Sigaev wrote:
Currently, json_agg, jsonb_agg, json_object_agg and jsonb_object_agg do
type classification on their arguments on each call to the transition
function. This is quite unnecessary, as the argument types won't change.
This patch remedies the defect by caching the necessary values in the
aggregate state object.

While this doesn't change the performance much, since these functions
are essentially dominated by other bits of the processing, I think it is
nevertheless worth doing.

After quick observation of your patch, why don't you use FmgrInfo instead of JsonAggState.val_output_func/JsonAggState.key_category? FmgrInfo could be filled by fmgr_info_cxt() in aggcontext memory context. Suppose, direct usage of FmgrInfo with FunctionCall a bit faster than OidFunctionCall.

Well, we need the category to help data_to_json(b) do its work. Nevertheless, it might be doable to pass an FmgrInfo* to datum_to_json. I'll see what I can do.



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