feat: consume and produce Substrait type extensions

datafusion/substrait/src/extensions.rs

@@ -0,0 +1,157 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use datafusion::common::{plan_err, DataFusionError};
+use std::collections::HashMap;
+use substrait::proto::extensions::simple_extension_declaration::{
+    ExtensionFunction, ExtensionType, ExtensionTypeVariation, MappingType,
+};
+use substrait::proto::extensions::SimpleExtensionDeclaration;
+
+/// Substrait uses [SimpleExtensions](https://substrait.io/extensions/#simple-extensions) to define
+/// behavior of plans in addition to what's supported directly by the protobuf definitions.
+/// That includes functions, but also provides support for custom types and variations for existing
+/// types. This structs facilitates the use of these extensions in DataFusion.
+/// TODO: DF doesn't yet use extensions for type variations <https://github.com/apache/datafusion/issues/11544>
+/// TODO: DF doesn't yet provide valid extensionUris <https://github.com/apache/datafusion/issues/11545>
+#[derive(Default, Debug, PartialEq)]
+pub struct Extensions {
+    pub functions: HashMap<u32, String>, // anchor -> function name
+    pub types: HashMap<u32, String>,     // anchor -> type name
+    pub type_variations: HashMap<u32, String>, // anchor -> type variation name
+}
+
+impl Extensions {
+    /// Registers a function and returns the anchor (reference) to it. If the function has already
+    /// been registered, it returns the existing anchor.
+    /// Function names are case-insensitive (converted to lowercase).
+    pub fn register_function(&mut self, function_name: String) -> u32 {
+        let function_name = function_name.to_lowercase();
+
+        // Some functions are named differently in Substrait default extensions than in DF
+        // Rename those to match the Substrait extensions for interoperability
+        let function_name = match function_name.as_str() {
+            "substr" => "substring".to_string(),
+            _ => function_name,
+        };
+
+        match self.functions.iter().find(|(_, f)| *f == &function_name) {
+            Some((function_anchor, _)) => *function_anchor, // Function has been registered
+            None => {
+                // Function has NOT been registered
+                let function_anchor = self.functions.len() as u32;
+                self.functions
+                    .insert(function_anchor, function_name.clone());
+                function_anchor
+            }
+        }
+    }
+
+    /// Registers a type and returns the anchor (reference) to it. If the type has already
+    /// been registered, it returns the existing anchor.
+    pub fn register_type(&mut self, type_name: String) -> u32 {
+        let type_name = type_name.to_lowercase();
+        match self.types.iter().find(|(_, t)| *t == &type_name) {
+            Some((type_anchor, _)) => *type_anchor, // Type has been registered
+            None => {
+                // Type has NOT been registered
+                let type_anchor = self.types.len() as u32;
+                self.types.insert(type_anchor, type_name.clone());
+                type_anchor
+            }
+        }
+    }
+}
+
+impl TryFrom<&Vec<SimpleExtensionDeclaration>> for Extensions {
+    type Error = DataFusionError;
+
+    fn try_from(
+        value: &Vec<SimpleExtensionDeclaration>,
+    ) -> datafusion::common::Result<Self> {
+        let mut functions = HashMap::new();
+        let mut types = HashMap::new();
+        let mut type_variations = HashMap::new();
+
+        for ext in value {
+            match &ext.mapping_type {
+                Some(MappingType::ExtensionFunction(ext_f)) => {
+                    functions.insert(ext_f.function_anchor, ext_f.name.to_owned());
+                }
+                Some(MappingType::ExtensionType(ext_t)) => {
+                    types.insert(ext_t.type_anchor, ext_t.name.to_owned());
+                }
+                Some(MappingType::ExtensionTypeVariation(ext_v)) => {
+                    type_variations
+                        .insert(ext_v.type_variation_anchor, ext_v.name.to_owned());
+                }
+                None => return plan_err!("Cannot parse empty extension"),
+            }
+        }
+
+        Ok(Extensions {
+            functions,
+            types,
+            type_variations,
+        })
+    }
+}
+
+impl From<Extensions> for Vec<SimpleExtensionDeclaration> {
+    fn from(val: Extensions) -> Vec<SimpleExtensionDeclaration> {
+        let mut extensions = vec![];
+        for (f_anchor, f_name) in val.functions {
+            let function_extension = ExtensionFunction {
+                extension_uri_reference: u32::MAX,
+                function_anchor: f_anchor,
+                name: f_name,
+            };
+            let simple_extension = SimpleExtensionDeclaration {
+                mapping_type: Some(MappingType::ExtensionFunction(function_extension)),
+            };
+            extensions.push(simple_extension);
+        }
+
+        for (t_anchor, t_name) in val.types {
+            let type_extension = ExtensionType {
+                extension_uri_reference: u32::MAX, // https://github.com/apache/datafusion/issues/11545
+                type_anchor: t_anchor,
+                name: t_name,
+            };
+            let simple_extension = SimpleExtensionDeclaration {
+                mapping_type: Some(MappingType::ExtensionType(type_extension)),
+            };
+            extensions.push(simple_extension);
+        }
+
+        for (tv_anchor, tv_name) in val.type_variations {
+            let type_variation_extension = ExtensionTypeVariation {
+                extension_uri_reference: u32::MAX, // We don't register proper extension URIs yet
+                type_variation_anchor: tv_anchor,
+                name: tv_name,
+            };
+            let simple_extension = SimpleExtensionDeclaration {
+                mapping_type: Some(MappingType::ExtensionTypeVariation(
+                    type_variation_extension,
+                )),
+            };
+            extensions.push(simple_extension);
+        }
+
+        extensions
+    }
+}

datafusion/substrait/src/lib.rs

@@ -72,6 +72,7 @@
 //! # Ok(())
 //! # }
 //! ```
+pub mod extensions;
 pub mod logical_plan;
 pub mod physical_plan;
 pub mod serializer;