paleolimbot commented on code in PR #20312:
URL: https://github.com/apache/datafusion/pull/20312#discussion_r2995241541
##########
datafusion-examples/examples/extension_types/temperature.rs:
##########
@@ -181,45 +212,69 @@ impl ExtensionType for TemperatureExtensionType {
data_type: &DataType,
metadata: Self::Metadata,
) -> std::result::Result<Self, ArrowError> {
- let instance = Self(metadata);
+ let instance = Self::new(data_type.clone(), metadata);
instance.supports_data_type(data_type)?;
Ok(instance)
}
}
/// Implementation of [`DFExtensionType`] for [`TemperatureExtensionType`].
+///
+/// This implements the trait for customizing DataFusion.
impl DFExtensionType for TemperatureExtensionType {
+ fn storage_type(&self) -> DataType {
+ self.storage_type.clone()
+ }
+
+ fn serialize_metadata(&self) -> Option<String> {
+ ExtensionType::serialize_metadata(self)
+ }
+
fn create_array_formatter<'fmt>(
&self,
array: &'fmt dyn Array,
options: &FormatOptions<'fmt>,
) -> Result<Option<ArrayFormatter<'fmt>>> {
- if array.data_type() != &DataType::Float64 {
- return internal_err!("Wrong array type for Temperature");
+ match self.storage_type {
+ DataType::Float32 => {
Review Comment:
This is indeed more verbose...if I were writing this today I would probably
just cast `array` to `Float64` and format since that particular cast isn't
expensive in the context of printing stuff, but I think this example is great
as is.
##########
datafusion/core/src/extension_types/array_formatter_factory.rs:
##########
@@ -0,0 +1,67 @@
+// 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 arrow::array::Array;
+use arrow::util::display::{ArrayFormatter, ArrayFormatterFactory,
FormatOptions};
+use arrow_schema::{ArrowError, Field};
+use datafusion_expr::registry::ExtensionTypeRegistryRef;
+
+/// A factory for creating [`ArrayFormatter`]s that checks whether a
registered extension type can
+/// format a given array based on its metadata.
+#[derive(Debug)]
+pub struct DFArrayFormatterFactory {
+ /// The extension type registry
+ registry: ExtensionTypeRegistryRef,
+}
Review Comment:
Sorry for not catching this on the previous pass, but this feels like an odd
place for the formatter factory (printing values happen in lower level crates
quite a lot)...I think this would make more sense next to the registry in
datafusion-expr.
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