zhengruifeng commented on code in PR #39068:
URL: https://github.com/apache/spark/pull/39068#discussion_r1049238906
##########
python/pyspark/sql/connect/functions.py:
##########
@@ -79,6 +85,84 @@ def _invoke_binary_math_function(name: str, col1: Any, col2:
Any) -> Column:
return _invoke_function(name, *_cols)
+def _get_lambda_parameters(f: Callable) -> ValuesView[inspect.Parameter]:
+ signature = inspect.signature(f)
+ parameters = signature.parameters.values()
+
+ # We should exclude functions that use
+ # variable args and keyword argnames
+ # as well as keyword only args
+ supported_parameter_types = {
+ inspect.Parameter.POSITIONAL_OR_KEYWORD,
+ inspect.Parameter.POSITIONAL_ONLY,
+ }
+
+ # Validate that
+ # function arity is between 1 and 3
+ if not (1 <= len(parameters) <= 3):
+ raise ValueError(
+ "f should take between 1 and 3 arguments, but provided function
takes {}".format(
+ len(parameters)
+ )
+ )
+
+ # and all arguments can be used as positional
+ if not all(p.kind in supported_parameter_types for p in parameters):
+ raise ValueError("f should use only POSITIONAL or POSITIONAL OR
KEYWORD arguments")
+
+ return parameters
+
+
+def _create_lambda(f: Callable) -> LambdaFunction:
+ """
+ Create `o.a.s.sql.expressions.LambdaFunction` corresponding
+ to transformation described by f
+
+ :param f: A Python of one of the following forms:
+ - (Column) -> Column: ...
+ - (Column, Column) -> Column: ...
+ - (Column, Column, Column) -> Column: ...
+ """
+ parameters = _get_lambda_parameters(f)
+
+ arg_names = ["x", "y", "z"]
+
+ arg_cols: List[Column] = []
+ for arg in arg_names[: len(parameters)]:
+ # TODO: How to make sure lambda variable names are unique? RPC for
increasing ID?
Review Comment:
PySpark invokes `UnresolvedNamedLambdaVariable.freshVarName` in JVM to get a
unique variable name
```
object UnresolvedNamedLambdaVariable {
// Counter to ensure lambda variable names are unique
private val nextVarNameId = new AtomicInteger(0)
def freshVarName(name: String): String = {
s"${name}_${nextVarNameId.getAndIncrement()}"
}
}
```
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