To define a builtin function that is collected by the Function systable at compile time, use BUILTIN_RETTYPE, BUILTIN_FUNC, and BUILTIN_ARGTYPE macros to define that in any source file in src/.
These macros must be appear on three consecutive lines with no leading spaces/tabs in the same order as below.
The return and argument types need to be some SQL type known to the system at compile time. For instance, to define a function f with a funcid = 1000 that accepts INT4 and INT2 typed arguments and returns a INT4, add the following lines (BUILTIN_xxx macros must appear at the beginning of the lines with no space) to some source file in src/. The funcid must be unique across all systable rows and will be checked at compile time for duplication.
BUILTIN_RETTYPE(INT4) BUILTIN_FUNC(f, 1000) BUILTIN_ARGTYPE(INT4, INT2) BUILTIN_OPR(ADD) // only needed if defining a operator { // implementation of f }
You'd also need to add the file that contains the builtin function to the list FILES_WITH_BUILTIN_FUNCS in src/utils/CMakeLists.txt.
