arrow_schema/
field.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
3// distributed with this work for additional information
4// regarding copyright ownership.  The ASF licenses this file
5// to you under the Apache License, Version 2.0 (the
6// "License"); you may not use this file except in compliance
7// with the License.  You may obtain a copy of the License at
8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing,
12// software distributed under the License is distributed on an
13// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14// KIND, either express or implied.  See the License for the
15// specific language governing permissions and limitations
16// under the License.
17
18use crate::error::ArrowError;
19use std::cmp::Ordering;
20use std::collections::HashMap;
21use std::hash::{Hash, Hasher};
22use std::sync::Arc;
23
24use crate::datatype::DataType;
25#[cfg(feature = "canonical_extension_types")]
26use crate::extension::CanonicalExtensionType;
27use crate::schema::SchemaBuilder;
28use crate::{
29    extension::{ExtensionType, EXTENSION_TYPE_METADATA_KEY, EXTENSION_TYPE_NAME_KEY},
30    Fields, UnionFields, UnionMode,
31};
32
33/// A reference counted [`Field`]
34pub type FieldRef = Arc<Field>;
35
36/// Describes a single column in a [`Schema`](super::Schema).
37///
38/// A [`Schema`](super::Schema) is an ordered collection of
39/// [`Field`] objects. Fields contain:
40/// * `name`: the name of the field
41/// * `data_type`: the type of the field
42/// * `nullable`: if the field is nullable
43/// * `metadata`: a map of key-value pairs containing additional custom metadata
44///
45/// Arrow Extension types, are encoded in `Field`s metadata. See
46/// [`Self::try_extension_type`] to retrieve the [`ExtensionType`], if any.
47#[derive(Debug, Clone)]
48#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
49pub struct Field {
50    name: String,
51    data_type: DataType,
52    nullable: bool,
53    #[deprecated(
54        since = "54.0.0",
55        note = "The ability to preserve dictionary IDs will be removed. With it, all fields related to it."
56    )]
57    dict_id: i64,
58    dict_is_ordered: bool,
59    /// A map of key-value pairs containing additional custom meta data.
60    metadata: HashMap<String, String>,
61}
62
63// Auto-derive `PartialEq` traits will pull `dict_id` and `dict_is_ordered`
64// into comparison. However, these properties are only used in IPC context
65// for matching dictionary encoded data. They are not necessary to be same
66// to consider schema equality. For example, in C++ `Field` implementation,
67// it doesn't contain these dictionary properties too.
68impl PartialEq for Field {
69    fn eq(&self, other: &Self) -> bool {
70        self.name == other.name
71            && self.data_type == other.data_type
72            && self.nullable == other.nullable
73            && self.metadata == other.metadata
74    }
75}
76
77impl Eq for Field {}
78
79impl PartialOrd for Field {
80    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
81        Some(self.cmp(other))
82    }
83}
84
85impl Ord for Field {
86    fn cmp(&self, other: &Self) -> Ordering {
87        self.name
88            .cmp(other.name())
89            .then_with(|| self.data_type.cmp(other.data_type()))
90            .then_with(|| self.nullable.cmp(&other.nullable))
91            .then_with(|| {
92                // ensure deterministic key order
93                let mut keys: Vec<&String> =
94                    self.metadata.keys().chain(other.metadata.keys()).collect();
95                keys.sort();
96                for k in keys {
97                    match (self.metadata.get(k), other.metadata.get(k)) {
98                        (None, None) => {}
99                        (Some(_), None) => {
100                            return Ordering::Less;
101                        }
102                        (None, Some(_)) => {
103                            return Ordering::Greater;
104                        }
105                        (Some(v1), Some(v2)) => match v1.cmp(v2) {
106                            Ordering::Equal => {}
107                            other => {
108                                return other;
109                            }
110                        },
111                    }
112                }
113
114                Ordering::Equal
115            })
116    }
117}
118
119impl Hash for Field {
120    fn hash<H: Hasher>(&self, state: &mut H) {
121        self.name.hash(state);
122        self.data_type.hash(state);
123        self.nullable.hash(state);
124
125        // ensure deterministic key order
126        let mut keys: Vec<&String> = self.metadata.keys().collect();
127        keys.sort();
128        for k in keys {
129            k.hash(state);
130            self.metadata.get(k).expect("key valid").hash(state);
131        }
132    }
133}
134
135impl Field {
136    /// Default list member field name
137    pub const LIST_FIELD_DEFAULT_NAME: &'static str = "item";
138
139    /// Creates a new field with the given name, data type, and nullability
140    ///
141    /// # Example
142    /// ```
143    /// # use arrow_schema::{Field, DataType};
144    /// Field::new("field_name", DataType::Int32, true);
145    /// ```
146    pub fn new(name: impl Into<String>, data_type: DataType, nullable: bool) -> Self {
147        #[allow(deprecated)]
148        Field {
149            name: name.into(),
150            data_type,
151            nullable,
152            dict_id: 0,
153            dict_is_ordered: false,
154            metadata: HashMap::default(),
155        }
156    }
157
158    /// Creates a new `Field` suitable for [`DataType::List`] and
159    /// [`DataType::LargeList`]
160    ///
161    /// While not required, this method follows the convention of naming the
162    /// `Field` `"item"`.
163    ///
164    /// # Example
165    /// ```
166    /// # use arrow_schema::{Field, DataType};
167    /// assert_eq!(
168    ///   Field::new("item", DataType::Int32, true),
169    ///   Field::new_list_field(DataType::Int32, true)
170    /// );
171    /// ```
172    pub fn new_list_field(data_type: DataType, nullable: bool) -> Self {
173        Self::new(Self::LIST_FIELD_DEFAULT_NAME, data_type, nullable)
174    }
175
176    /// Creates a new field that has additional dictionary information
177    #[deprecated(
178        since = "54.0.0",
179        note = "The ability to preserve dictionary IDs will be removed. With the dict_id field disappearing this function signature will change by removing the dict_id parameter."
180    )]
181    pub fn new_dict(
182        name: impl Into<String>,
183        data_type: DataType,
184        nullable: bool,
185        dict_id: i64,
186        dict_is_ordered: bool,
187    ) -> Self {
188        #[allow(deprecated)]
189        Field {
190            name: name.into(),
191            data_type,
192            nullable,
193            dict_id,
194            dict_is_ordered,
195            metadata: HashMap::default(),
196        }
197    }
198
199    /// Create a new [`Field`] with [`DataType::Dictionary`]
200    ///
201    /// Use [`Self::new_dict`] for more advanced dictionary options
202    ///
203    /// # Panics
204    ///
205    /// Panics if [`!key.is_dictionary_key_type`][DataType::is_dictionary_key_type]
206    pub fn new_dictionary(
207        name: impl Into<String>,
208        key: DataType,
209        value: DataType,
210        nullable: bool,
211    ) -> Self {
212        assert!(
213            key.is_dictionary_key_type(),
214            "{key} is not a valid dictionary key"
215        );
216        let data_type = DataType::Dictionary(Box::new(key), Box::new(value));
217        Self::new(name, data_type, nullable)
218    }
219
220    /// Create a new [`Field`] with [`DataType::Struct`]
221    ///
222    /// - `name`: the name of the [`DataType::Struct`] field
223    /// - `fields`: the description of each struct element
224    /// - `nullable`: if the [`DataType::Struct`] array is nullable
225    pub fn new_struct(name: impl Into<String>, fields: impl Into<Fields>, nullable: bool) -> Self {
226        Self::new(name, DataType::Struct(fields.into()), nullable)
227    }
228
229    /// Create a new [`Field`] with [`DataType::List`]
230    ///
231    /// - `name`: the name of the [`DataType::List`] field
232    /// - `value`: the description of each list element
233    /// - `nullable`: if the [`DataType::List`] array is nullable
234    pub fn new_list(name: impl Into<String>, value: impl Into<FieldRef>, nullable: bool) -> Self {
235        Self::new(name, DataType::List(value.into()), nullable)
236    }
237
238    /// Create a new [`Field`] with [`DataType::LargeList`]
239    ///
240    /// - `name`: the name of the [`DataType::LargeList`] field
241    /// - `value`: the description of each list element
242    /// - `nullable`: if the [`DataType::LargeList`] array is nullable
243    pub fn new_large_list(
244        name: impl Into<String>,
245        value: impl Into<FieldRef>,
246        nullable: bool,
247    ) -> Self {
248        Self::new(name, DataType::LargeList(value.into()), nullable)
249    }
250
251    /// Create a new [`Field`] with [`DataType::FixedSizeList`]
252    ///
253    /// - `name`: the name of the [`DataType::FixedSizeList`] field
254    /// - `value`: the description of each list element
255    /// - `size`: the size of the fixed size list
256    /// - `nullable`: if the [`DataType::FixedSizeList`] array is nullable
257    pub fn new_fixed_size_list(
258        name: impl Into<String>,
259        value: impl Into<FieldRef>,
260        size: i32,
261        nullable: bool,
262    ) -> Self {
263        Self::new(name, DataType::FixedSizeList(value.into(), size), nullable)
264    }
265
266    /// Create a new [`Field`] with [`DataType::Map`]
267    ///
268    /// - `name`: the name of the [`DataType::Map`] field
269    /// - `entries`: the name of the inner [`DataType::Struct`] field
270    /// - `keys`: the map keys
271    /// - `values`: the map values
272    /// - `sorted`: if the [`DataType::Map`] array is sorted
273    /// - `nullable`: if the [`DataType::Map`] array is nullable
274    pub fn new_map(
275        name: impl Into<String>,
276        entries: impl Into<String>,
277        keys: impl Into<FieldRef>,
278        values: impl Into<FieldRef>,
279        sorted: bool,
280        nullable: bool,
281    ) -> Self {
282        let data_type = DataType::Map(
283            Arc::new(Field::new(
284                entries.into(),
285                DataType::Struct(Fields::from([keys.into(), values.into()])),
286                false, // The inner map field is always non-nullable (#1697),
287            )),
288            sorted,
289        );
290        Self::new(name, data_type, nullable)
291    }
292
293    /// Create a new [`Field`] with [`DataType::Union`]
294    ///
295    /// - `name`: the name of the [`DataType::Union`] field
296    /// - `type_ids`: the union type ids
297    /// - `fields`: the union fields
298    /// - `mode`: the union mode
299    pub fn new_union<S, F, T>(name: S, type_ids: T, fields: F, mode: UnionMode) -> Self
300    where
301        S: Into<String>,
302        F: IntoIterator,
303        F::Item: Into<FieldRef>,
304        T: IntoIterator<Item = i8>,
305    {
306        Self::new(
307            name,
308            DataType::Union(UnionFields::new(type_ids, fields), mode),
309            false, // Unions cannot be nullable
310        )
311    }
312
313    /// Sets the `Field`'s optional custom metadata.
314    #[inline]
315    pub fn set_metadata(&mut self, metadata: HashMap<String, String>) {
316        self.metadata = metadata;
317    }
318
319    /// Sets the metadata of this `Field` to be `metadata` and returns self
320    pub fn with_metadata(mut self, metadata: HashMap<String, String>) -> Self {
321        self.set_metadata(metadata);
322        self
323    }
324
325    /// Returns the immutable reference to the `Field`'s optional custom metadata.
326    #[inline]
327    pub const fn metadata(&self) -> &HashMap<String, String> {
328        &self.metadata
329    }
330
331    /// Returns a mutable reference to the `Field`'s optional custom metadata.
332    #[inline]
333    pub fn metadata_mut(&mut self) -> &mut HashMap<String, String> {
334        &mut self.metadata
335    }
336
337    /// Returns an immutable reference to the `Field`'s name.
338    #[inline]
339    pub const fn name(&self) -> &String {
340        &self.name
341    }
342
343    /// Set the name of this [`Field`]
344    #[inline]
345    pub fn set_name(&mut self, name: impl Into<String>) {
346        self.name = name.into();
347    }
348
349    /// Set the name of the [`Field`] and returns self.
350    ///
351    /// ```
352    /// # use arrow_schema::*;
353    /// let field = Field::new("c1", DataType::Int64, false)
354    ///    .with_name("c2");
355    ///
356    /// assert_eq!(field.name(), "c2");
357    /// ```
358    pub fn with_name(mut self, name: impl Into<String>) -> Self {
359        self.set_name(name);
360        self
361    }
362
363    /// Returns an immutable reference to the [`Field`]'s  [`DataType`].
364    #[inline]
365    pub const fn data_type(&self) -> &DataType {
366        &self.data_type
367    }
368
369    /// Set [`DataType`] of the [`Field`]
370    ///
371    /// ```
372    /// # use arrow_schema::*;
373    /// let mut field = Field::new("c1", DataType::Int64, false);
374    /// field.set_data_type(DataType::Utf8);
375    ///
376    /// assert_eq!(field.data_type(), &DataType::Utf8);
377    /// ```
378    #[inline]
379    pub fn set_data_type(&mut self, data_type: DataType) {
380        self.data_type = data_type;
381    }
382
383    /// Set [`DataType`] of the [`Field`] and returns self.
384    ///
385    /// ```
386    /// # use arrow_schema::*;
387    /// let field = Field::new("c1", DataType::Int64, false)
388    ///    .with_data_type(DataType::Utf8);
389    ///
390    /// assert_eq!(field.data_type(), &DataType::Utf8);
391    /// ```
392    pub fn with_data_type(mut self, data_type: DataType) -> Self {
393        self.set_data_type(data_type);
394        self
395    }
396
397    /// Returns the extension type name of this [`Field`], if set.
398    ///
399    /// This returns the value of [`EXTENSION_TYPE_NAME_KEY`], if set in
400    /// [`Field::metadata`]. If the key is missing, there is no extension type
401    /// name and this returns `None`.
402    ///
403    /// # Example
404    ///
405    /// ```
406    /// # use arrow_schema::{DataType, extension::EXTENSION_TYPE_NAME_KEY, Field};
407    ///
408    /// let field = Field::new("", DataType::Null, false);
409    /// assert_eq!(field.extension_type_name(), None);
410    ///
411    /// let field = Field::new("", DataType::Null, false).with_metadata(
412    ///    [(EXTENSION_TYPE_NAME_KEY.to_owned(), "example".to_owned())]
413    ///        .into_iter()
414    ///        .collect(),
415    /// );
416    /// assert_eq!(field.extension_type_name(), Some("example"));
417    /// ```
418    pub fn extension_type_name(&self) -> Option<&str> {
419        self.metadata()
420            .get(EXTENSION_TYPE_NAME_KEY)
421            .map(String::as_ref)
422    }
423
424    /// Returns the extension type metadata of this [`Field`], if set.
425    ///
426    /// This returns the value of [`EXTENSION_TYPE_METADATA_KEY`], if set in
427    /// [`Field::metadata`]. If the key is missing, there is no extension type
428    /// metadata and this returns `None`.
429    ///
430    /// # Example
431    ///
432    /// ```
433    /// # use arrow_schema::{DataType, extension::EXTENSION_TYPE_METADATA_KEY, Field};
434    ///
435    /// let field = Field::new("", DataType::Null, false);
436    /// assert_eq!(field.extension_type_metadata(), None);
437    ///
438    /// let field = Field::new("", DataType::Null, false).with_metadata(
439    ///    [(EXTENSION_TYPE_METADATA_KEY.to_owned(), "example".to_owned())]
440    ///        .into_iter()
441    ///        .collect(),
442    /// );
443    /// assert_eq!(field.extension_type_metadata(), Some("example"));
444    /// ```
445    pub fn extension_type_metadata(&self) -> Option<&str> {
446        self.metadata()
447            .get(EXTENSION_TYPE_METADATA_KEY)
448            .map(String::as_ref)
449    }
450
451    /// Returns an instance of the given [`ExtensionType`] of this [`Field`],
452    /// if set in the [`Field::metadata`].
453    ///
454    /// # Error
455    ///
456    /// Returns an error if
457    /// - this field does not have the name of this extension type
458    ///   ([`ExtensionType::NAME`]) in the [`Field::metadata`] (mismatch or
459    ///   missing)
460    /// - the deserialization of the metadata
461    ///   ([`ExtensionType::deserialize_metadata`]) fails
462    /// - the construction of the extension type ([`ExtensionType::try_new`])
463    ///   fail (for example when the [`Field::data_type`] is not supported by
464    ///   the extension type ([`ExtensionType::supports_data_type`]))
465    pub fn try_extension_type<E: ExtensionType>(&self) -> Result<E, ArrowError> {
466        // Check the extension name in the metadata
467        match self.extension_type_name() {
468            // It should match the name of the given extension type
469            Some(name) if name == E::NAME => {
470                // Deserialize the metadata and try to construct the extension
471                // type
472                E::deserialize_metadata(self.extension_type_metadata())
473                    .and_then(|metadata| E::try_new(self.data_type(), metadata))
474            }
475            // Name mismatch
476            Some(name) => Err(ArrowError::InvalidArgumentError(format!(
477                "Field extension type name mismatch, expected {}, found {name}",
478                E::NAME
479            ))),
480            // Name missing
481            None => Err(ArrowError::InvalidArgumentError(
482                "Field extension type name missing".to_owned(),
483            )),
484        }
485    }
486
487    /// Returns an instance of the given [`ExtensionType`] of this [`Field`],
488    /// panics if this [`Field`] does not have this extension type.
489    ///
490    /// # Panic
491    ///
492    /// This calls [`Field::try_extension_type`] and panics when it returns an
493    /// error.
494    pub fn extension_type<E: ExtensionType>(&self) -> E {
495        self.try_extension_type::<E>()
496            .unwrap_or_else(|e| panic!("{e}"))
497    }
498
499    /// Updates the metadata of this [`Field`] with the [`ExtensionType::NAME`]
500    /// and [`ExtensionType::metadata`] of the given [`ExtensionType`], if the
501    /// given extension type supports the [`Field::data_type`] of this field
502    /// ([`ExtensionType::supports_data_type`]).
503    ///
504    /// If the given extension type defines no metadata, a previously set
505    /// value of [`EXTENSION_TYPE_METADATA_KEY`] is cleared.
506    ///
507    /// # Error
508    ///
509    /// This functions returns an error if the data type of this field does not
510    /// match any of the supported storage types of the given extension type.
511    pub fn try_with_extension_type<E: ExtensionType>(
512        &mut self,
513        extension_type: E,
514    ) -> Result<(), ArrowError> {
515        // Make sure the data type of this field is supported
516        extension_type.supports_data_type(&self.data_type)?;
517
518        self.metadata
519            .insert(EXTENSION_TYPE_NAME_KEY.to_owned(), E::NAME.to_owned());
520        match extension_type.serialize_metadata() {
521            Some(metadata) => self
522                .metadata
523                .insert(EXTENSION_TYPE_METADATA_KEY.to_owned(), metadata),
524            // If this extension type has no metadata, we make sure to
525            // clear previously set metadata.
526            None => self.metadata.remove(EXTENSION_TYPE_METADATA_KEY),
527        };
528
529        Ok(())
530    }
531
532    /// Updates the metadata of this [`Field`] with the [`ExtensionType::NAME`]
533    /// and [`ExtensionType::metadata`] of the given [`ExtensionType`].
534    ///
535    /// # Panics
536    ///
537    /// This calls [`Field::try_with_extension_type`] and panics when it
538    /// returns an error.
539    pub fn with_extension_type<E: ExtensionType>(mut self, extension_type: E) -> Self {
540        self.try_with_extension_type(extension_type)
541            .unwrap_or_else(|e| panic!("{e}"));
542        self
543    }
544
545    /// Returns the [`CanonicalExtensionType`] of this [`Field`], if set.
546    ///
547    /// # Error
548    ///
549    /// Returns an error if
550    /// - this field does have a canonical extension type (mismatch or missing)
551    /// - the canonical extension is not supported
552    /// - the construction of the extension type fails
553    #[cfg(feature = "canonical_extension_types")]
554    pub fn try_canonical_extension_type(&self) -> Result<CanonicalExtensionType, ArrowError> {
555        CanonicalExtensionType::try_from(self)
556    }
557
558    /// Indicates whether this [`Field`] supports null values.
559    ///
560    /// If true, the field *may* contain null values.
561    #[inline]
562    pub const fn is_nullable(&self) -> bool {
563        self.nullable
564    }
565
566    /// Set the `nullable` of this [`Field`].
567    ///
568    /// ```
569    /// # use arrow_schema::*;
570    /// let mut field = Field::new("c1", DataType::Int64, false);
571    /// field.set_nullable(true);
572    ///
573    /// assert_eq!(field.is_nullable(), true);
574    /// ```
575    #[inline]
576    pub fn set_nullable(&mut self, nullable: bool) {
577        self.nullable = nullable;
578    }
579
580    /// Set `nullable` of the [`Field`] and returns self.
581    ///
582    /// ```
583    /// # use arrow_schema::*;
584    /// let field = Field::new("c1", DataType::Int64, false)
585    ///    .with_nullable(true);
586    ///
587    /// assert_eq!(field.is_nullable(), true);
588    /// ```
589    pub fn with_nullable(mut self, nullable: bool) -> Self {
590        self.set_nullable(nullable);
591        self
592    }
593
594    /// Returns a (flattened) [`Vec`] containing all child [`Field`]s
595    /// within `self` contained within this field (including `self`)
596    pub(crate) fn fields(&self) -> Vec<&Field> {
597        let mut collected_fields = vec![self];
598        collected_fields.append(&mut Field::_fields(&self.data_type));
599
600        collected_fields
601    }
602
603    fn _fields(dt: &DataType) -> Vec<&Field> {
604        match dt {
605            DataType::Struct(fields) => fields.iter().flat_map(|f| f.fields()).collect(),
606            DataType::Union(fields, _) => fields.iter().flat_map(|(_, f)| f.fields()).collect(),
607            DataType::List(field)
608            | DataType::LargeList(field)
609            | DataType::FixedSizeList(field, _)
610            | DataType::Map(field, _) => field.fields(),
611            DataType::Dictionary(_, value_field) => Field::_fields(value_field.as_ref()),
612            DataType::RunEndEncoded(_, field) => field.fields(),
613            _ => vec![],
614        }
615    }
616
617    /// Returns a vector containing all (potentially nested) `Field` instances selected by the
618    /// dictionary ID they use
619    #[inline]
620    #[deprecated(
621        since = "54.0.0",
622        note = "The ability to preserve dictionary IDs will be removed. With it, all fields related to it."
623    )]
624    pub(crate) fn fields_with_dict_id(&self, id: i64) -> Vec<&Field> {
625        self.fields()
626            .into_iter()
627            .filter(|&field| {
628                #[allow(deprecated)]
629                let matching_dict_id = field.dict_id == id;
630                matches!(field.data_type(), DataType::Dictionary(_, _)) && matching_dict_id
631            })
632            .collect()
633    }
634
635    /// Returns the dictionary ID, if this is a dictionary type.
636    #[inline]
637    #[deprecated(
638        since = "54.0.0",
639        note = "The ability to preserve dictionary IDs will be removed. With it, all fields related to it."
640    )]
641    pub const fn dict_id(&self) -> Option<i64> {
642        match self.data_type {
643            #[allow(deprecated)]
644            DataType::Dictionary(_, _) => Some(self.dict_id),
645            _ => None,
646        }
647    }
648
649    /// Returns whether this `Field`'s dictionary is ordered, if this is a dictionary type.
650    ///
651    /// # Example
652    /// ```
653    /// # use arrow_schema::{DataType, Field};
654    /// // non dictionaries do not have a dict is ordered flat
655    /// let field = Field::new("c1", DataType::Int64, false);
656    /// assert_eq!(field.dict_is_ordered(), None);
657    /// // by default dictionary is not ordered
658    /// let field = Field::new("c1", DataType::Dictionary(Box::new(DataType::Int64), Box::new(DataType::Utf8)), false);
659    /// assert_eq!(field.dict_is_ordered(), Some(false));
660    /// let field = field.with_dict_is_ordered(true);
661    /// assert_eq!(field.dict_is_ordered(), Some(true));
662    /// ```
663    #[inline]
664    pub const fn dict_is_ordered(&self) -> Option<bool> {
665        match self.data_type {
666            DataType::Dictionary(_, _) => Some(self.dict_is_ordered),
667            _ => None,
668        }
669    }
670
671    /// Set the is ordered field for this `Field`, if it is a dictionary.
672    ///
673    /// Does nothing if this is not a dictionary type.
674    ///
675    /// See [`Field::dict_is_ordered`] for more information.
676    pub fn with_dict_is_ordered(mut self, dict_is_ordered: bool) -> Self {
677        if matches!(self.data_type, DataType::Dictionary(_, _)) {
678            self.dict_is_ordered = dict_is_ordered;
679        };
680        self
681    }
682
683    /// Merge this field into self if it is compatible.
684    ///
685    /// Struct fields are merged recursively.
686    ///
687    /// NOTE: `self` may be updated to a partial / unexpected state in case of merge failure.
688    ///
689    /// Example:
690    ///
691    /// ```
692    /// # use arrow_schema::*;
693    /// let mut field = Field::new("c1", DataType::Int64, false);
694    /// assert!(field.try_merge(&Field::new("c1", DataType::Int64, true)).is_ok());
695    /// assert!(field.is_nullable());
696    /// ```
697    pub fn try_merge(&mut self, from: &Field) -> Result<(), ArrowError> {
698        if from.dict_is_ordered != self.dict_is_ordered {
699            return Err(ArrowError::SchemaError(format!(
700                "Fail to merge schema field '{}' because from dict_is_ordered = {} does not match {}",
701                self.name, from.dict_is_ordered, self.dict_is_ordered
702            )));
703        }
704        // merge metadata
705        match (self.metadata().is_empty(), from.metadata().is_empty()) {
706            (false, false) => {
707                let mut merged = self.metadata().clone();
708                for (key, from_value) in from.metadata() {
709                    if let Some(self_value) = self.metadata.get(key) {
710                        if self_value != from_value {
711                            return Err(ArrowError::SchemaError(format!(
712                                "Fail to merge field '{}' due to conflicting metadata data value for key {}.
713                                    From value = {} does not match {}", self.name, key, from_value, self_value),
714                            ));
715                        }
716                    } else {
717                        merged.insert(key.clone(), from_value.clone());
718                    }
719                }
720                self.set_metadata(merged);
721            }
722            (true, false) => {
723                self.set_metadata(from.metadata().clone());
724            }
725            _ => {}
726        }
727        match &mut self.data_type {
728            DataType::Struct(nested_fields) => match &from.data_type {
729                DataType::Struct(from_nested_fields) => {
730                    let mut builder = SchemaBuilder::new();
731                    nested_fields.iter().chain(from_nested_fields).try_for_each(|f| builder.try_merge(f))?;
732                    *nested_fields = builder.finish().fields;
733                }
734                _ => {
735                    return Err(ArrowError::SchemaError(
736                        format!("Fail to merge schema field '{}' because the from data_type = {} is not DataType::Struct",
737                            self.name, from.data_type)
738                ))}
739            },
740            DataType::Union(nested_fields, _) => match &from.data_type {
741                DataType::Union(from_nested_fields, _) => {
742                    nested_fields.try_merge(from_nested_fields)?
743                }
744                _ => {
745                    return Err(ArrowError::SchemaError(
746                        format!("Fail to merge schema field '{}' because the from data_type = {} is not DataType::Union",
747                            self.name, from.data_type)
748                    ));
749                }
750            },
751            DataType::List(field) => match &from.data_type {
752                DataType::List(from_field) => {
753                    let mut f = (**field).clone();
754                    f.try_merge(from_field)?;
755                    (*field) = Arc::new(f);
756                },
757                _ => {
758                    return Err(ArrowError::SchemaError(
759                        format!("Fail to merge schema field '{}' because the from data_type = {} is not DataType::List",
760                            self.name, from.data_type)
761                ))}
762            },
763            DataType::LargeList(field) => match &from.data_type {
764                DataType::LargeList(from_field) => {
765                    let mut f = (**field).clone();
766                    f.try_merge(from_field)?;
767                    (*field) = Arc::new(f);
768                },
769                _ => {
770                    return Err(ArrowError::SchemaError(
771                        format!("Fail to merge schema field '{}' because the from data_type = {} is not DataType::LargeList",
772                            self.name, from.data_type)
773                ))}
774            },
775            DataType::Null => {
776                self.nullable = true;
777                self.data_type = from.data_type.clone();
778            }
779            | DataType::Boolean
780            | DataType::Int8
781            | DataType::Int16
782            | DataType::Int32
783            | DataType::Int64
784            | DataType::UInt8
785            | DataType::UInt16
786            | DataType::UInt32
787            | DataType::UInt64
788            | DataType::Float16
789            | DataType::Float32
790            | DataType::Float64
791            | DataType::Timestamp(_, _)
792            | DataType::Date32
793            | DataType::Date64
794            | DataType::Time32(_)
795            | DataType::Time64(_)
796            | DataType::Duration(_)
797            | DataType::Binary
798            | DataType::LargeBinary
799            | DataType::BinaryView
800            | DataType::Interval(_)
801            | DataType::LargeListView(_)
802            | DataType::ListView(_)
803            | DataType::Map(_, _)
804            | DataType::Dictionary(_, _)
805            | DataType::RunEndEncoded(_, _)
806            | DataType::FixedSizeList(_, _)
807            | DataType::FixedSizeBinary(_)
808            | DataType::Utf8
809            | DataType::LargeUtf8
810            | DataType::Utf8View
811            | DataType::Decimal32(_, _)
812            | DataType::Decimal64(_, _)
813            | DataType::Decimal128(_, _)
814            | DataType::Decimal256(_, _) => {
815                if from.data_type == DataType::Null {
816                    self.nullable = true;
817                } else if self.data_type != from.data_type {
818                    return Err(ArrowError::SchemaError(
819                        format!("Fail to merge schema field '{}' because the from data_type = {} does not equal {}",
820                            self.name, from.data_type, self.data_type)
821                    ));
822                }
823            }
824        }
825        self.nullable |= from.nullable;
826
827        Ok(())
828    }
829
830    /// Check to see if `self` is a superset of `other` field. Superset is defined as:
831    ///
832    /// * if nullability doesn't match, self needs to be nullable
833    /// * self.metadata is a superset of other.metadata
834    /// * all other fields are equal
835    pub fn contains(&self, other: &Field) -> bool {
836        self.name == other.name
837        && self.data_type.contains(&other.data_type)
838        && self.dict_is_ordered == other.dict_is_ordered
839        // self need to be nullable or both of them are not nullable
840        && (self.nullable || !other.nullable)
841        // make sure self.metadata is a superset of other.metadata
842        && other.metadata.iter().all(|(k, v1)| {
843            self.metadata.get(k).map(|v2| v1 == v2).unwrap_or_default()
844        })
845    }
846
847    /// Return size of this instance in bytes.
848    ///
849    /// Includes the size of `Self`.
850    pub fn size(&self) -> usize {
851        std::mem::size_of_val(self) - std::mem::size_of_val(&self.data_type)
852            + self.data_type.size()
853            + self.name.capacity()
854            + (std::mem::size_of::<(String, String)>() * self.metadata.capacity())
855            + self
856                .metadata
857                .iter()
858                .map(|(k, v)| k.capacity() + v.capacity())
859                .sum::<usize>()
860    }
861}
862
863// TODO: improve display with crate https://crates.io/crates/derive_more ?
864impl std::fmt::Display for Field {
865    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
866        write!(f, "{self:?}")
867    }
868}
869
870#[cfg(test)]
871mod test {
872    use super::*;
873    use std::collections::hash_map::DefaultHasher;
874
875    #[test]
876    fn test_new_with_string() {
877        // Fields should allow owned Strings to support reuse
878        let s = "c1";
879        Field::new(s, DataType::Int64, false);
880    }
881
882    #[test]
883    fn test_new_dict_with_string() {
884        // Fields should allow owned Strings to support reuse
885        let s = "c1";
886        #[allow(deprecated)]
887        Field::new_dict(s, DataType::Int64, false, 4, false);
888    }
889
890    #[test]
891    fn test_merge_incompatible_types() {
892        let mut field = Field::new("c1", DataType::Int64, false);
893        let result = field
894            .try_merge(&Field::new("c1", DataType::Float32, true))
895            .expect_err("should fail")
896            .to_string();
897        assert_eq!("Schema error: Fail to merge schema field 'c1' because the from data_type = Float32 does not equal Int64", result);
898    }
899
900    #[test]
901    fn test_merge_with_null() {
902        let mut field1 = Field::new("c1", DataType::Null, true);
903        field1
904            .try_merge(&Field::new("c1", DataType::Float32, false))
905            .expect("should widen type to nullable float");
906        assert_eq!(Field::new("c1", DataType::Float32, true), field1);
907
908        let mut field2 = Field::new("c2", DataType::Utf8, false);
909        field2
910            .try_merge(&Field::new("c2", DataType::Null, true))
911            .expect("should widen type to nullable utf8");
912        assert_eq!(Field::new("c2", DataType::Utf8, true), field2);
913    }
914
915    #[test]
916    fn test_merge_with_nested_null() {
917        let mut struct1 = Field::new(
918            "s1",
919            DataType::Struct(Fields::from(vec![Field::new(
920                "inner",
921                DataType::Float32,
922                false,
923            )])),
924            false,
925        );
926
927        let struct2 = Field::new(
928            "s2",
929            DataType::Struct(Fields::from(vec![Field::new(
930                "inner",
931                DataType::Null,
932                false,
933            )])),
934            true,
935        );
936
937        struct1
938            .try_merge(&struct2)
939            .expect("should widen inner field's type to nullable float");
940        assert_eq!(
941            Field::new(
942                "s1",
943                DataType::Struct(Fields::from(vec![Field::new(
944                    "inner",
945                    DataType::Float32,
946                    true,
947                )])),
948                true,
949            ),
950            struct1
951        );
952
953        let mut list1 = Field::new(
954            "l1",
955            DataType::List(Field::new("inner", DataType::Float32, false).into()),
956            false,
957        );
958
959        let list2 = Field::new(
960            "l2",
961            DataType::List(Field::new("inner", DataType::Null, false).into()),
962            true,
963        );
964
965        list1
966            .try_merge(&list2)
967            .expect("should widen inner field's type to nullable float");
968        assert_eq!(
969            Field::new(
970                "l1",
971                DataType::List(Field::new("inner", DataType::Float32, true).into()),
972                true,
973            ),
974            list1
975        );
976
977        let mut large_list1 = Field::new(
978            "ll1",
979            DataType::LargeList(Field::new("inner", DataType::Float32, false).into()),
980            false,
981        );
982
983        let large_list2 = Field::new(
984            "ll2",
985            DataType::LargeList(Field::new("inner", DataType::Null, false).into()),
986            true,
987        );
988
989        large_list1
990            .try_merge(&large_list2)
991            .expect("should widen inner field's type to nullable float");
992        assert_eq!(
993            Field::new(
994                "ll1",
995                DataType::LargeList(Field::new("inner", DataType::Float32, true).into()),
996                true,
997            ),
998            large_list1
999        );
1000    }
1001
1002    #[test]
1003    fn test_fields_with_dict_id() {
1004        #[allow(deprecated)]
1005        let dict1 = Field::new_dict(
1006            "dict1",
1007            DataType::Dictionary(DataType::Utf8.into(), DataType::Int32.into()),
1008            false,
1009            10,
1010            false,
1011        );
1012        #[allow(deprecated)]
1013        let dict2 = Field::new_dict(
1014            "dict2",
1015            DataType::Dictionary(DataType::Int32.into(), DataType::Int8.into()),
1016            false,
1017            20,
1018            false,
1019        );
1020
1021        let field = Field::new(
1022            "struct<dict1, list[struct<dict2, list[struct<dict1]>]>",
1023            DataType::Struct(Fields::from(vec![
1024                dict1.clone(),
1025                Field::new(
1026                    "list[struct<dict1, list[struct<dict2>]>]",
1027                    DataType::List(Arc::new(Field::new(
1028                        "struct<dict1, list[struct<dict2>]>",
1029                        DataType::Struct(Fields::from(vec![
1030                            dict1.clone(),
1031                            Field::new(
1032                                "list[struct<dict2>]",
1033                                DataType::List(Arc::new(Field::new(
1034                                    "struct<dict2>",
1035                                    DataType::Struct(vec![dict2.clone()].into()),
1036                                    false,
1037                                ))),
1038                                false,
1039                            ),
1040                        ])),
1041                        false,
1042                    ))),
1043                    false,
1044                ),
1045            ])),
1046            false,
1047        );
1048
1049        #[allow(deprecated)]
1050        for field in field.fields_with_dict_id(10) {
1051            assert_eq!(dict1, *field);
1052        }
1053        #[allow(deprecated)]
1054        for field in field.fields_with_dict_id(20) {
1055            assert_eq!(dict2, *field);
1056        }
1057    }
1058
1059    fn get_field_hash(field: &Field) -> u64 {
1060        let mut s = DefaultHasher::new();
1061        field.hash(&mut s);
1062        s.finish()
1063    }
1064
1065    #[test]
1066    fn test_field_comparison_case() {
1067        // dictionary-encoding properties not used for field comparison
1068        #[allow(deprecated)]
1069        let dict1 = Field::new_dict(
1070            "dict1",
1071            DataType::Dictionary(DataType::Utf8.into(), DataType::Int32.into()),
1072            false,
1073            10,
1074            false,
1075        );
1076        #[allow(deprecated)]
1077        let dict2 = Field::new_dict(
1078            "dict1",
1079            DataType::Dictionary(DataType::Utf8.into(), DataType::Int32.into()),
1080            false,
1081            20,
1082            false,
1083        );
1084
1085        assert_eq!(dict1, dict2);
1086        assert_eq!(get_field_hash(&dict1), get_field_hash(&dict2));
1087
1088        #[allow(deprecated)]
1089        let dict1 = Field::new_dict(
1090            "dict0",
1091            DataType::Dictionary(DataType::Utf8.into(), DataType::Int32.into()),
1092            false,
1093            10,
1094            false,
1095        );
1096
1097        assert_ne!(dict1, dict2);
1098        assert_ne!(get_field_hash(&dict1), get_field_hash(&dict2));
1099    }
1100
1101    #[test]
1102    fn test_field_comparison_metadata() {
1103        let f1 = Field::new("x", DataType::Binary, false).with_metadata(HashMap::from([
1104            (String::from("k1"), String::from("v1")),
1105            (String::from("k2"), String::from("v2")),
1106        ]));
1107        let f2 = Field::new("x", DataType::Binary, false).with_metadata(HashMap::from([
1108            (String::from("k1"), String::from("v1")),
1109            (String::from("k3"), String::from("v3")),
1110        ]));
1111        let f3 = Field::new("x", DataType::Binary, false).with_metadata(HashMap::from([
1112            (String::from("k1"), String::from("v1")),
1113            (String::from("k3"), String::from("v4")),
1114        ]));
1115
1116        assert!(f1.cmp(&f2).is_lt());
1117        assert!(f2.cmp(&f3).is_lt());
1118        assert!(f1.cmp(&f3).is_lt());
1119    }
1120
1121    #[test]
1122    fn test_contains_reflexivity() {
1123        let mut field = Field::new("field1", DataType::Float16, false);
1124        field.set_metadata(HashMap::from([
1125            (String::from("k0"), String::from("v0")),
1126            (String::from("k1"), String::from("v1")),
1127        ]));
1128        assert!(field.contains(&field))
1129    }
1130
1131    #[test]
1132    fn test_contains_transitivity() {
1133        let child_field = Field::new("child1", DataType::Float16, false);
1134
1135        let mut field1 = Field::new(
1136            "field1",
1137            DataType::Struct(Fields::from(vec![child_field])),
1138            false,
1139        );
1140        field1.set_metadata(HashMap::from([(String::from("k1"), String::from("v1"))]));
1141
1142        let mut field2 = Field::new("field1", DataType::Struct(Fields::default()), true);
1143        field2.set_metadata(HashMap::from([(String::from("k2"), String::from("v2"))]));
1144        field2.try_merge(&field1).unwrap();
1145
1146        let mut field3 = Field::new("field1", DataType::Struct(Fields::default()), false);
1147        field3.set_metadata(HashMap::from([(String::from("k3"), String::from("v3"))]));
1148        field3.try_merge(&field2).unwrap();
1149
1150        assert!(field2.contains(&field1));
1151        assert!(field3.contains(&field2));
1152        assert!(field3.contains(&field1));
1153
1154        assert!(!field1.contains(&field2));
1155        assert!(!field1.contains(&field3));
1156        assert!(!field2.contains(&field3));
1157    }
1158
1159    #[test]
1160    fn test_contains_nullable() {
1161        let field1 = Field::new("field1", DataType::Boolean, true);
1162        let field2 = Field::new("field1", DataType::Boolean, false);
1163        assert!(field1.contains(&field2));
1164        assert!(!field2.contains(&field1));
1165    }
1166
1167    #[test]
1168    fn test_contains_must_have_same_fields() {
1169        let child_field1 = Field::new("child1", DataType::Float16, false);
1170        let child_field2 = Field::new("child2", DataType::Float16, false);
1171
1172        let field1 = Field::new(
1173            "field1",
1174            DataType::Struct(vec![child_field1.clone()].into()),
1175            true,
1176        );
1177        let field2 = Field::new(
1178            "field1",
1179            DataType::Struct(vec![child_field1, child_field2].into()),
1180            true,
1181        );
1182
1183        assert!(!field1.contains(&field2));
1184        assert!(!field2.contains(&field1));
1185
1186        // UnionFields with different type ID
1187        let field1 = Field::new(
1188            "field1",
1189            DataType::Union(
1190                UnionFields::new(
1191                    vec![1, 2],
1192                    vec![
1193                        Field::new("field1", DataType::UInt8, true),
1194                        Field::new("field3", DataType::Utf8, false),
1195                    ],
1196                ),
1197                UnionMode::Dense,
1198            ),
1199            true,
1200        );
1201        let field2 = Field::new(
1202            "field1",
1203            DataType::Union(
1204                UnionFields::new(
1205                    vec![1, 3],
1206                    vec![
1207                        Field::new("field1", DataType::UInt8, false),
1208                        Field::new("field3", DataType::Utf8, false),
1209                    ],
1210                ),
1211                UnionMode::Dense,
1212            ),
1213            true,
1214        );
1215        assert!(!field1.contains(&field2));
1216
1217        // UnionFields with same type ID
1218        let field1 = Field::new(
1219            "field1",
1220            DataType::Union(
1221                UnionFields::new(
1222                    vec![1, 2],
1223                    vec![
1224                        Field::new("field1", DataType::UInt8, true),
1225                        Field::new("field3", DataType::Utf8, false),
1226                    ],
1227                ),
1228                UnionMode::Dense,
1229            ),
1230            true,
1231        );
1232        let field2 = Field::new(
1233            "field1",
1234            DataType::Union(
1235                UnionFields::new(
1236                    vec![1, 2],
1237                    vec![
1238                        Field::new("field1", DataType::UInt8, false),
1239                        Field::new("field3", DataType::Utf8, false),
1240                    ],
1241                ),
1242                UnionMode::Dense,
1243            ),
1244            true,
1245        );
1246        assert!(field1.contains(&field2));
1247    }
1248
1249    #[cfg(feature = "serde")]
1250    fn assert_binary_serde_round_trip(field: Field) {
1251        let serialized = bincode::serialize(&field).unwrap();
1252        let deserialized: Field = bincode::deserialize(&serialized).unwrap();
1253        assert_eq!(field, deserialized)
1254    }
1255
1256    #[cfg(feature = "serde")]
1257    #[test]
1258    fn test_field_without_metadata_serde() {
1259        let field = Field::new("name", DataType::Boolean, true);
1260        assert_binary_serde_round_trip(field)
1261    }
1262
1263    #[cfg(feature = "serde")]
1264    #[test]
1265    fn test_field_with_empty_metadata_serde() {
1266        let field = Field::new("name", DataType::Boolean, false).with_metadata(HashMap::new());
1267
1268        assert_binary_serde_round_trip(field)
1269    }
1270
1271    #[cfg(feature = "serde")]
1272    #[test]
1273    fn test_field_with_nonempty_metadata_serde() {
1274        let mut metadata = HashMap::new();
1275        metadata.insert("hi".to_owned(), "".to_owned());
1276        let field = Field::new("name", DataType::Boolean, false).with_metadata(metadata);
1277
1278        assert_binary_serde_round_trip(field)
1279    }
1280}
arrow_schema/field.rs

arrow_schema/
field.rs
