- i think you can use the fctx->current variable without temporary variable (there's comment in the add_var function: Full version of add functionality on variable level (handling signs). result might point to one of the operands too without danger.). But you _must_ switch the context first because add_var will allocate new array for the data and freeing the old one.
Yep.
- numeric can be NaN. We must reject it as first, finish and last parameter.
Makes sense.
- numeric datatype is large, but there are limitations. According to doc, the limit is: up to 131072 digits before the decimal point; up to 16383 digits after the decimal point. How can we check if the next step overflows? As a comparison, in int.c, generate_series_step_int4 checks if its overflows, and stop the next call by setting step to 0. Should we do that?
Yes we should.
- while testing regression test, opr_sanity checks that the generate_series_numeric function is used twice (once for 2 parameter and once for the 3 parameter function), so i changed the name to generate_series_step_numeric and created new function generate_series_numeric that calls generate_series_step_numeric.
Yep.
It seems to me that this patch is heading in a good direction (haven't tested or tried to break it, just looked at the code). However please be careful of code format, particularly brackets for "if" blocks. For example this thing: