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Map AvroSchema to Arrow (#4886) #5009
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// 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. | ||
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use crate::schema::{ComplexType, PrimitiveType, Record, Schema, TypeName}; | ||
use arrow_schema::{ | ||
ArrowError, DataType, Field, FieldRef, IntervalUnit, SchemaBuilder, SchemaRef, TimeUnit, | ||
}; | ||
use std::borrow::Cow; | ||
use std::collections::HashMap; | ||
use std::sync::Arc; | ||
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/// Avro types are not nullable, with nullability instead encoded as a union | ||
/// where one of the variants is the null type. | ||
/// | ||
/// To accommodate this we special case two-variant unions where one of the | ||
/// variants is the null type, and use this to derive arrow's notion of nullability | ||
#[derive(Debug, Copy, Clone)] | ||
enum Nulls { | ||
/// The nulls are encoded as the first union variant | ||
NullFirst, | ||
/// The nulls are encoded as the second union variant | ||
NullSecond, | ||
} | ||
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/// An Avro field mapped to the arrow data model | ||
#[derive(Debug, Clone)] | ||
pub struct AvroField { | ||
nulls: Option<Nulls>, | ||
meta: Arc<AvroFieldMeta>, | ||
} | ||
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#[derive(Debug, Clone)] | ||
struct AvroFieldMeta { | ||
name: String, | ||
metadata: HashMap<String, String>, | ||
codec: Codec, | ||
} | ||
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impl AvroField { | ||
/// Returns the arrow [`Field`] | ||
pub fn field(&self) -> Field { | ||
let d = self.meta.codec.data_type(); | ||
Field::new(&self.meta.name, d, self.nulls.is_some()) | ||
.with_metadata(self.meta.metadata.clone()) | ||
} | ||
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/// Returns the [`Codec`] | ||
pub fn codec(&self) -> &Codec { | ||
&self.meta.codec | ||
} | ||
} | ||
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impl<'a> TryFrom<&Schema<'a>> for AvroField { | ||
type Error = ArrowError; | ||
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fn try_from(schema: &Schema<'a>) -> Result<Self, Self::Error> { | ||
let mut resolver = Resolver::default(); | ||
make_field(schema, "item", None, &mut resolver) | ||
} | ||
} | ||
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#[derive(Debug, Clone)] | ||
pub enum Codec { | ||
Null, | ||
Boolean, | ||
Int32, | ||
Int64, | ||
Float32, | ||
Float64, | ||
Binary, | ||
Utf8, | ||
Date32, | ||
TimeMillis, | ||
TimeMicros, | ||
/// Timestamp (is_utc) | ||
TimestampMillis(bool), | ||
TimestampMicros(bool), | ||
Fixed(i32), | ||
List(Arc<AvroField>), | ||
Struct(Arc<[AvroField]>), | ||
Duration, | ||
} | ||
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impl Codec { | ||
fn data_type(&self) -> DataType { | ||
match self { | ||
Self::Null => DataType::Null, | ||
Self::Boolean => DataType::Boolean, | ||
Self::Int32 => DataType::Int32, | ||
Self::Int64 => DataType::Int64, | ||
Self::Float32 => DataType::Float32, | ||
Self::Float64 => DataType::Float64, | ||
Self::Binary => DataType::Binary, | ||
Self::Utf8 => DataType::Utf8, | ||
Self::Date32 => DataType::Date32, | ||
Self::TimeMillis => DataType::Time32(TimeUnit::Millisecond), | ||
Self::TimeMicros => DataType::Time64(TimeUnit::Microsecond), | ||
Self::TimestampMillis(is_utc) => { | ||
DataType::Timestamp(TimeUnit::Millisecond, is_utc.then(|| "+00:00".into())) | ||
} | ||
Self::TimestampMicros(is_utc) => { | ||
DataType::Timestamp(TimeUnit::Microsecond, is_utc.then(|| "+00:00".into())) | ||
} | ||
Self::Duration => DataType::Interval(IntervalUnit::MonthDayNano), | ||
Self::Fixed(size) => DataType::FixedSizeBinary(*size), | ||
Self::List(f) => DataType::List(Arc::new(f.field())), | ||
Self::Struct(f) => DataType::Struct(f.iter().map(|x| x.field()).collect()), | ||
} | ||
} | ||
} | ||
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impl From<PrimitiveType> for Codec { | ||
fn from(value: PrimitiveType) -> Self { | ||
match value { | ||
PrimitiveType::Null => Self::Null, | ||
PrimitiveType::Boolean => Self::Boolean, | ||
PrimitiveType::Int => Self::Int32, | ||
PrimitiveType::Long => Self::Int64, | ||
PrimitiveType::Float => Self::Float32, | ||
PrimitiveType::Double => Self::Float64, | ||
PrimitiveType::Bytes => Self::Binary, | ||
PrimitiveType::String => Self::Utf8, | ||
} | ||
} | ||
} | ||
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#[derive(Debug, Default)] | ||
struct Resolver<'a> { | ||
map: HashMap<(&'a str, &'a str), AvroField>, | ||
} | ||
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impl<'a> Resolver<'a> { | ||
fn register(&mut self, name: &'a str, namespace: Option<&'a str>, schema: AvroField) { | ||
self.map.insert((name, namespace.unwrap_or("")), schema); | ||
} | ||
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fn resolve(&self, name: &str, namespace: Option<&'a str>) -> Result<AvroField, ArrowError> { | ||
let (namespace, name) = name | ||
.rsplit_once('.') | ||
.unwrap_or_else(|| (namespace.unwrap_or(""), name)); | ||
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self.map | ||
.get(&(namespace, name)) | ||
.ok_or_else(|| ArrowError::ParseError(format!("Failed to resolve {namespace}.{name}"))) | ||
.cloned() | ||
} | ||
} | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. This could use some docstrings. For once: what's a namespace and why is the top-level namespace |
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fn make_field<'a>( | ||
schema: &Schema<'a>, | ||
name: &'a str, | ||
namespace: Option<&'a str>, | ||
resolver: &mut Resolver<'a>, | ||
) -> Result<AvroField, ArrowError> { | ||
match schema { | ||
Schema::TypeName(TypeName::Primitive(p)) => Ok(AvroField { | ||
nulls: None, | ||
meta: Arc::new(AvroFieldMeta { | ||
name: name.to_string(), | ||
metadata: Default::default(), | ||
codec: (*p).into(), | ||
}), | ||
}), | ||
Schema::TypeName(TypeName::Ref(name)) => resolver.resolve(name, namespace), | ||
Schema::Union(f) => { | ||
let null = f | ||
.iter() | ||
.position(|x| x == &Schema::TypeName(TypeName::Primitive(PrimitiveType::Null))); | ||
match (f.len() == 2, null) { | ||
(true, Some(0)) => { | ||
let mut field = make_field(&f[1], name, namespace, resolver)?; | ||
field.nulls = Some(Nulls::NullFirst); | ||
Ok(field) | ||
} | ||
(true, Some(1)) => { | ||
let mut field = make_field(&f[0], name, namespace, resolver)?; | ||
field.nulls = Some(Nulls::NullSecond); | ||
Ok(field) | ||
} | ||
_ => Err(ArrowError::NotYetImplemented(format!( | ||
"Union of {f:?} not currently supported" | ||
))), | ||
} | ||
} | ||
Schema::Complex(c) => match c { | ||
ComplexType::Record(r) => { | ||
let namespace = r.namespace.or(namespace); | ||
let fields = r | ||
.fields | ||
.iter() | ||
.map(|field| make_field(&field.r#type, field.name, namespace, resolver)) | ||
.collect::<Result<_, _>>()?; | ||
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let field = AvroField { | ||
nulls: None, | ||
meta: Arc::new(AvroFieldMeta { | ||
name: r.name.to_string(), | ||
codec: Codec::Struct(fields), | ||
metadata: extract_metadata(&r.attributes.additional), | ||
}), | ||
}; | ||
resolver.register(name, namespace, field.clone()); | ||
Ok(field) | ||
} | ||
ComplexType::Array(a) => { | ||
let mut field = make_field(a.items.as_ref(), "item", namespace, resolver)?; | ||
Ok(AvroField { | ||
nulls: None, | ||
meta: Arc::new(AvroFieldMeta { | ||
name: name.to_string(), | ||
metadata: extract_metadata(&a.attributes.additional), | ||
codec: Codec::List(Arc::new(field)), | ||
}), | ||
}) | ||
} | ||
ComplexType::Fixed(f) => { | ||
let size = f.size.try_into().map_err(|e| { | ||
ArrowError::ParseError(format!("Overflow converting size to i32: {e}")) | ||
})?; | ||
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let field = AvroField { | ||
nulls: None, | ||
meta: Arc::new(AvroFieldMeta { | ||
name: f.name.to_string(), | ||
metadata: extract_metadata(&f.attributes.additional), | ||
codec: Codec::Fixed(size), | ||
}), | ||
}; | ||
resolver.register(f.name, namespace, field.clone()); | ||
Ok(field) | ||
} | ||
ComplexType::Enum(e) => Err(ArrowError::NotYetImplemented(format!( | ||
"Enum of {e:?} not currently supported" | ||
))), | ||
ComplexType::Map(m) => Err(ArrowError::NotYetImplemented(format!( | ||
"Map of {m:?} not currently supported" | ||
))), | ||
}, | ||
Schema::Type(t) => { | ||
let mut field = make_field( | ||
&Schema::TypeName(t.r#type.clone()), | ||
name, | ||
namespace, | ||
resolver, | ||
)?; | ||
let meta = Arc::make_mut(&mut field.meta); | ||
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// https://avro.apache.org/docs/1.11.1/specification/#logical-types | ||
match (t.attributes.logical_type, &mut meta.codec) { | ||
(Some("decimal"), c @ Codec::Fixed(_)) => { | ||
return Err(ArrowError::NotYetImplemented( | ||
"Decimals are not currently supported".to_string(), | ||
)) | ||
} | ||
(Some("date"), c @ Codec::Int32) => *c = Codec::Date32, | ||
(Some("time-millis"), c @ Codec::Int32) => *c = Codec::TimeMillis, | ||
(Some("time-micros"), c @ Codec::Int64) => *c = Codec::TimeMicros, | ||
(Some("timestamp-millis"), c @ Codec::Int64) => *c = Codec::TimestampMillis(true), | ||
(Some("timestamp-micros"), c @ Codec::Int64) => *c = Codec::TimestampMicros(true), | ||
(Some("local-timestamp-millis"), c @ Codec::Int64) => { | ||
*c = Codec::TimestampMillis(false) | ||
} | ||
(Some("local-timestamp-micros"), c @ Codec::Int64) => { | ||
*c = Codec::TimestampMicros(false) | ||
} | ||
(Some("duration"), c @ Codec::Fixed(12)) => *c = Codec::Duration, | ||
(Some(logical), _) => { | ||
// Insert unrecognized logical type into metadata map | ||
meta.metadata.insert("logicalType".into(), logical.into()); | ||
} | ||
(None, _) => {} | ||
} | ||
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if !t.attributes.additional.is_empty() { | ||
for (k, v) in &t.attributes.additional { | ||
meta.metadata.insert(k.to_string(), v.to_string()); | ||
} | ||
} | ||
Ok(field) | ||
} | ||
} | ||
} | ||
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fn extract_metadata(metadata: &HashMap<&str, serde_json::Value>) -> HashMap<String, String> { | ||
metadata | ||
.iter() | ||
.map(|(k, v)| (k.to_string(), v.to_string())) | ||
.collect() | ||
} |
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mod compression; | ||
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mod codec; | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. This is all kept crate-private to allow us to revisit this design as things evolve |
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#[cfg(test)] | ||
mod test_util { | ||
pub fn arrow_test_data(path: &str) -> String { | ||
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There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
This whole setup is rather annoying, but necessary to provide a reasonable API