feat: add builders for aggregate, window funcs and if-then

src/substrait/builders/extended_expression.py

@@ -0,0 +1,374 @@
+import itertools
+import substrait.gen.proto.algebra_pb2 as stalg
+import substrait.gen.proto.type_pb2 as stp
+import substrait.gen.proto.extended_expression_pb2 as stee
+import substrait.gen.proto.extensions.extensions_pb2 as ste
+from substrait.extension_registry import ExtensionRegistry
+from substrait.utils import type_num_names, merge_extension_uris, merge_extension_declarations
+from substrait.type_inference import infer_extended_expression_schema
+from typing import Callable, Any, Union, Iterable
+
+UnboundExtendedExpression = Callable[[stp.NamedStruct, ExtensionRegistry], stee.ExtendedExpression]
+
+def literal(value: Any, type: stp.Type, alias: str = None) -> UnboundExtendedExpression:
+    """Builds a resolver for ExtendedExpression containing a literal expression"""
+    def resolve(base_schema: stp.NamedStruct, registry: ExtensionRegistry) -> stee.ExtendedExpression:
+        kind = type.WhichOneof('kind')
+
+        if kind == "bool":
+            literal = stalg.Expression.Literal(boolean=value, nullable=type.bool.nullability == stp.Type.NULLABILITY_NULLABLE)
+        elif kind == "i8":
+            literal = stalg.Expression.Literal(i8=value, nullable=type.i8.nullability == stp.Type.NULLABILITY_NULLABLE)
+        elif kind == "i16":
+            literal = stalg.Expression.Literal(i16=value, nullable=type.i16.nullability == stp.Type.NULLABILITY_NULLABLE)
+        elif kind == "i32":
+            literal = stalg.Expression.Literal(i32=value, nullable=type.i32.nullability == stp.Type.NULLABILITY_NULLABLE)
+        elif kind == "i64":
+            literal = stalg.Expression.Literal(i64=value, nullable=type.i64.nullability == stp.Type.NULLABILITY_NULLABLE)
+        elif kind == "fp32":
+            literal = stalg.Expression.Literal(fp32=value, nullable=type.fp32.nullability == stp.Type.NULLABILITY_NULLABLE)
+        elif kind == "fp64":
+            literal = stalg.Expression.Literal(fp64=value, nullable=type.fp64.nullability == stp.Type.NULLABILITY_NULLABLE)
+        elif kind == "string":
+            literal = stalg.Expression.Literal(string=value, nullable=type.string.nullability == stp.Type.NULLABILITY_NULLABLE)
+        else:
+            raise Exception(f"Unknown literal type - {type}")
+
+        return stee.ExtendedExpression(
+            referred_expr=[
+                stee.ExpressionReference(
+                    expression=stalg.Expression(
+                        literal=literal
+                    ),
+                    output_names=[alias if alias else f'literal_{kind}'],
+                )
+            ],
+            base_schema=base_schema,
+        )
+
+    return resolve
+
+def column(field: Union[str, int], alias: str = None):
+    """Builds a resolver for ExtendedExpression containing a FieldReference expression
+
+    Accepts either an index or a field name of a desired field.
+    """
+
+    def resolve(
+        base_schema: stp.NamedStruct, registry: ExtensionRegistry
+    ) -> stee.ExtendedExpression:
+        lengths = [type_num_names(t) for t in base_schema.struct.types]
+        flat_indices = [0] + list(itertools.accumulate(lengths))[:-1]
+
+        if isinstance(field, str):
+            column_index = list(base_schema.names).index(field)
+            field_index = flat_indices.index(column_index)
+        else:
+            field_index = field
+
+        names_start = flat_indices[field_index]
+        names_end = (
+            flat_indices[field_index + 1]
+            if len(flat_indices) > field_index + 1
+            else None
+        )
+
+        return stee.ExtendedExpression(
+            referred_expr=[
+                stee.ExpressionReference(
+                    expression=stalg.Expression(
+                        selection=stalg.Expression.FieldReference(
+                            root_reference=stalg.Expression.FieldReference.RootReference(),
+                            direct_reference=stalg.Expression.ReferenceSegment(
+                                struct_field=stalg.Expression.ReferenceSegment.StructField(
+                                    field=field_index
+                                )
+                            ),
+                        )
+                    ),
+                    output_names=list(base_schema.names)[names_start:names_end]
+                    if not alias
+                    else [alias],
+                )
+            ],
+            base_schema=base_schema,
+        )
+
+    return resolve
+
+def scalar_function(
+    uri: str, function: str, *expressions: UnboundExtendedExpression, alias: str = None
+):
+    """Builds a resolver for ExtendedExpression containing a ScalarFunction expression"""
+
+    def resolve(
+        base_schema: stp.NamedStruct, registry: ExtensionRegistry
+    ) -> stee.ExtendedExpression:
+        bound_expressions: Iterable[stee.ExtendedExpression] = [
+            e(base_schema, registry) for e in expressions
+        ]
+
+        expression_schemas = [
+            infer_extended_expression_schema(b) for b in bound_expressions
+        ]
+
+        signature = [typ for es in expression_schemas for typ in es.types]
+
+        func = registry.lookup_function(uri, function, signature)
+
+        if not func:
+            raise Exception(f"Unknown function {function} for {signature}")
+
+        func_extension_uris = [
+            ste.SimpleExtensionURI(
+                extension_uri_anchor=registry.lookup_uri(uri), uri=uri
+            )
+        ]
+
+        func_extensions = [
+            ste.SimpleExtensionDeclaration(
+                extension_function=ste.SimpleExtensionDeclaration.ExtensionFunction(
+                    extension_uri_reference=registry.lookup_uri(uri),
+                    function_anchor=func[0].anchor,
+                    name=function,
+                )
+            )
+        ]
+
+        extension_uris = merge_extension_uris(
+            func_extension_uris, *[b.extension_uris for b in bound_expressions]
+        )
+
+        extensions = merge_extension_declarations(
+            func_extensions, *[b.extensions for b in bound_expressions]
+        )
+
+        return stee.ExtendedExpression(
+            referred_expr=[
+                stee.ExpressionReference(
+                    expression=stalg.Expression(
+                        scalar_function=stalg.Expression.ScalarFunction(
+                            function_reference=func[0].anchor,
+                            arguments=[
+                                stalg.FunctionArgument(
+                                    value=e.referred_expr[0].expression
+                                )
+                                for e in bound_expressions
+                            ],
+                            output_type=func[1],
+                        )
+                    ),
+                    output_names=[alias if alias else "scalar_function"],
+                )
+            ],
+            base_schema=base_schema,
+            extension_uris=extension_uris,
+            extensions=extensions,
+        )
+
+    return resolve
+
+def aggregate_function(
+    uri: str, function: str, *expressions: UnboundExtendedExpression, alias: str = None
+):
+    """Builds a resolver for ExtendedExpression containing a AggregateFunction measure"""
+
+    def resolve(
+        base_schema: stp.NamedStruct, registry: ExtensionRegistry
+    ) -> stee.ExtendedExpression:
+        bound_expressions: Iterable[stee.ExtendedExpression] = [
+            e(base_schema, registry) for e in expressions
+        ]
+
+        expression_schemas = [
+            infer_extended_expression_schema(b) for b in bound_expressions
+        ]
+
+        signature = [typ for es in expression_schemas for typ in es.types]
+
+        func = registry.lookup_function(uri, function, signature)
+
+        if not func:
+            raise Exception(f"Unknown function {function} for {signature}")
+
+        func_extension_uris = [
+            ste.SimpleExtensionURI(
+                extension_uri_anchor=registry.lookup_uri(uri), uri=uri
+            )
+        ]
+
+        func_extensions = [
+            ste.SimpleExtensionDeclaration(
+                extension_function=ste.SimpleExtensionDeclaration.ExtensionFunction(
+                    extension_uri_reference=registry.lookup_uri(uri),
+                    function_anchor=func[0].anchor,
+                    name=function,
+                )
+            )
+        ]
+
+        extension_uris = merge_extension_uris(
+            func_extension_uris, *[b.extension_uris for b in bound_expressions]
+        )
+
+        extensions = merge_extension_declarations(
+            func_extensions, *[b.extensions for b in bound_expressions]
+        )
+
+        return stee.ExtendedExpression(
+            referred_expr=[
+                stee.ExpressionReference(
+                    measure=stalg.AggregateFunction(
+                        function_reference=func[0].anchor,
+                        arguments=[
+                            stalg.FunctionArgument(value=e.referred_expr[0].expression)
+                            for e in bound_expressions
+                        ],
+                        output_type=func[1],
+                    ),
+                    output_names=[alias if alias else "aggregate_function"],
+                )
+            ],
+            base_schema=base_schema,
+            extension_uris=extension_uris,
+            extensions=extensions,
+        )
+
+    return resolve
+
+
+# TODO bounds, sorts
+def window_function(
+    uri: str,
+    function: str,
+    *expressions: UnboundExtendedExpression,
+    partitions: Iterable[UnboundExtendedExpression] = [],
+    alias: str = None,
+):
+    """Builds a resolver for ExtendedExpression containing a WindowFunction expression"""
+
+    def resolve(
+        base_schema: stp.NamedStruct, registry: ExtensionRegistry
+    ) -> stee.ExtendedExpression:
+        bound_expressions: Iterable[stee.ExtendedExpression] = [
+            e(base_schema, registry) for e in expressions
+        ]
+
+        bound_partitions = [e(base_schema, registry) for e in partitions]
+
+        expression_schemas = [
+            infer_extended_expression_schema(b) for b in bound_expressions
+        ]
+
+        signature = [typ for es in expression_schemas for typ in es.types]
+
+        func = registry.lookup_function(uri, function, signature)
+
+        if not func:
+            raise Exception(f"Unknown function {function} for {signature}")
+
+        func_extension_uris = [
+            ste.SimpleExtensionURI(
+                extension_uri_anchor=registry.lookup_uri(uri), uri=uri
+            )
+        ]
+
+        func_extensions = [
+            ste.SimpleExtensionDeclaration(
+                extension_function=ste.SimpleExtensionDeclaration.ExtensionFunction(
+                    extension_uri_reference=registry.lookup_uri(uri),
+                    function_anchor=func[0].anchor,
+                    name=function,
+                )
+            )
+        ]
+
+        extension_uris = merge_extension_uris(
+            func_extension_uris,
+            *[b.extension_uris for b in bound_expressions],
+            *[b.extension_uris for b in bound_partitions],
+        )
+
+        extensions = merge_extension_declarations(
+            func_extensions,
+            *[b.extensions for b in bound_expressions],
+            *[b.extensions for b in bound_partitions],
+        )
+
+        return stee.ExtendedExpression(
+            referred_expr=[
+                stee.ExpressionReference(
+                    expression=stalg.Expression(
+                        window_function=stalg.Expression.WindowFunction(
+                            function_reference=func[0].anchor,
+                            arguments=[
+                                stalg.FunctionArgument(
+                                    value=e.referred_expr[0].expression
+                                )
+                                for e in bound_expressions
+                            ],
+                            output_type=func[1],
+                            partitions=[
+                                e.referred_expr[0].expression for e in bound_partitions
+                            ],
+                        )
+                    ),
+                    output_names=[alias if alias else "window_function"],
+                )
+            ],
+            base_schema=base_schema,
+            extension_uris=extension_uris,
+            extensions=extensions,
+        )
+
+    return resolve
+
+
+def if_then(ifs: Iterable[tuple[UnboundExtendedExpression, UnboundExtendedExpression]], _else: UnboundExtendedExpression, alias: str = None):
+    """Builds a resolver for ExtendedExpression containing a IfThen expression"""
+    def resolve(
+        base_schema: stp.NamedStruct, registry: ExtensionRegistry
+    ) -> stee.ExtendedExpression:
+        bound_ifs = [
+            (if_clause[0](base_schema, registry), if_clause[1](base_schema, registry))
+            for if_clause in ifs
+        ]
+
+        bound_else = _else(base_schema, registry)
+
+        extension_uris = merge_extension_uris(
+            *[b[0].extension_uris for b in bound_ifs],
+            *[b[1].extension_uris for b in bound_ifs],
+            bound_else.extension_uris
+        )
+
+        extensions = merge_extension_declarations(
+            *[b[0].extensions for b in bound_ifs],
+            *[b[1].extensions for b in bound_ifs],
+            bound_else.extensions
+        )
+
+        return stee.ExtendedExpression(
+            referred_expr=[
+                stee.ExpressionReference(
+                    expression=stalg.Expression(
+                        if_then=stalg.Expression.IfThen(**{
+                            'ifs': [
+                                stalg.Expression.IfThen.IfClause(**{
+                                    'if': if_clause[0].referred_expr[0].expression,
+                                    'then': if_clause[1].referred_expr[0].expression,
+                                })    
+                                for if_clause in bound_ifs
+                            ],
+                            'else': bound_else.referred_expr[0].expression
+                        })
+                    ),
+                    output_names=[alias if alias else "if_then"],
+                )
+            ],
+            base_schema=base_schema,
+            extension_uris=extension_uris,
+            extensions=extensions,
+        )
+
+    return resolve