core_functions contains the set of functions that is included in the core system.
These functions are bundled with every installation of DuckDB.
In order to add new functions, add their definition to the functions.json file in the respective directory.
The function headers can then be generated from the set of functions using the following command:
python3 scripts/generate_functions.py
Function Format
Functions are defined according to the following format:
{
"name": "date_diff",
"parameters": "part,startdate,enddate",
"description": "The number of partition boundaries between the timestamps",
"example": "date_diff('hour', TIMESTAMPTZ '1992-09-30 23:59:59', TIMESTAMPTZ '1992-10-01 01:58:00')",
"type": "scalar_function_set",
"struct": "DateDiffFun",
"aliases": ["datediff"]
}
- name signifies the function name at the SQL level.
- parameters is a comma separated list of parameter names (for documentation purposes).
- description is a description of the function (for documentation purposes).
- example is an example of how to use the function (for documentation purposes).
- type is the type of function, e.g.
scalar_function,scalar_function_set,aggregate_function, etc. - struct is the optional name of the struct that holds the definition of the function in the generated header. By default the function name will be title cased with
Funadded to the end, e.g.date_diff->DateDiffFun. - aliases is an optional list of aliases for the function at the SQL level.
Scalar Function
Scalar functions require the following function to be defined:
ScalarFunction DateDiffFun::GetFunction() {
return ...
}
Scalar Function Set
Scalar function sets require the following function to be defined:
ScalarFunctionSet DateDiffFun::GetFunctions() {
return ...
}