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 an immutable reference to the `Field`'s name.
332    #[inline]
333    pub const fn name(&self) -> &String {
334        &self.name
335    }
336
337    /// Set the name of this [`Field`]
338    #[inline]
339    pub fn set_name(&mut self, name: impl Into<String>) {
340        self.name = name.into();
341    }
342
343    /// Set the name of the [`Field`] and returns self.
344    ///
345    /// ```
346    /// # use arrow_schema::*;
347    /// let field = Field::new("c1", DataType::Int64, false)
348    ///    .with_name("c2");
349    ///
350    /// assert_eq!(field.name(), "c2");
351    /// ```
352    pub fn with_name(mut self, name: impl Into<String>) -> Self {
353        self.set_name(name);
354        self
355    }
356
357    /// Returns an immutable reference to the [`Field`]'s  [`DataType`].
358    #[inline]
359    pub const fn data_type(&self) -> &DataType {
360        &self.data_type
361    }
362
363    /// Set [`DataType`] of the [`Field`]
364    ///
365    /// ```
366    /// # use arrow_schema::*;
367    /// let mut field = Field::new("c1", DataType::Int64, false);
368    /// field.set_data_type(DataType::Utf8);
369    ///
370    /// assert_eq!(field.data_type(), &DataType::Utf8);
371    /// ```
372    #[inline]
373    pub fn set_data_type(&mut self, data_type: DataType) {
374        self.data_type = data_type;
375    }
376
377    /// Set [`DataType`] of the [`Field`] and returns self.
378    ///
379    /// ```
380    /// # use arrow_schema::*;
381    /// let field = Field::new("c1", DataType::Int64, false)
382    ///    .with_data_type(DataType::Utf8);
383    ///
384    /// assert_eq!(field.data_type(), &DataType::Utf8);
385    /// ```
386    pub fn with_data_type(mut self, data_type: DataType) -> Self {
387        self.set_data_type(data_type);
388        self
389    }
390
391    /// Returns the extension type name of this [`Field`], if set.
392    ///
393    /// This returns the value of [`EXTENSION_TYPE_NAME_KEY`], if set in
394    /// [`Field::metadata`]. If the key is missing, there is no extension type
395    /// name and this returns `None`.
396    ///
397    /// # Example
398    ///
399    /// ```
400    /// # use arrow_schema::{DataType, extension::EXTENSION_TYPE_NAME_KEY, Field};
401    ///
402    /// let field = Field::new("", DataType::Null, false);
403    /// assert_eq!(field.extension_type_name(), None);
404    ///
405    /// let field = Field::new("", DataType::Null, false).with_metadata(
406    ///    [(EXTENSION_TYPE_NAME_KEY.to_owned(), "example".to_owned())]
407    ///        .into_iter()
408    ///        .collect(),
409    /// );
410    /// assert_eq!(field.extension_type_name(), Some("example"));
411    /// ```
412    pub fn extension_type_name(&self) -> Option<&str> {
413        self.metadata()
414            .get(EXTENSION_TYPE_NAME_KEY)
415            .map(String::as_ref)
416    }
417
418    /// Returns the extension type metadata of this [`Field`], if set.
419    ///
420    /// This returns the value of [`EXTENSION_TYPE_METADATA_KEY`], if set in
421    /// [`Field::metadata`]. If the key is missing, there is no extension type
422    /// metadata and this returns `None`.
423    ///
424    /// # Example
425    ///
426    /// ```
427    /// # use arrow_schema::{DataType, extension::EXTENSION_TYPE_METADATA_KEY, Field};
428    ///
429    /// let field = Field::new("", DataType::Null, false);
430    /// assert_eq!(field.extension_type_metadata(), None);
431    ///
432    /// let field = Field::new("", DataType::Null, false).with_metadata(
433    ///    [(EXTENSION_TYPE_METADATA_KEY.to_owned(), "example".to_owned())]
434    ///        .into_iter()
435    ///        .collect(),
436    /// );
437    /// assert_eq!(field.extension_type_metadata(), Some("example"));
438    /// ```
439    pub fn extension_type_metadata(&self) -> Option<&str> {
440        self.metadata()
441            .get(EXTENSION_TYPE_METADATA_KEY)
442            .map(String::as_ref)
443    }
444
445    /// Returns an instance of the given [`ExtensionType`] of this [`Field`],
446    /// if set in the [`Field::metadata`].
447    ///
448    /// # Error
449    ///
450    /// Returns an error if
451    /// - this field does not have the name of this extension type
452    ///   ([`ExtensionType::NAME`]) in the [`Field::metadata`] (mismatch or
453    ///   missing)
454    /// - the deserialization of the metadata
455    ///   ([`ExtensionType::deserialize_metadata`]) fails
456    /// - the construction of the extension type ([`ExtensionType::try_new`])
457    ///   fail (for example when the [`Field::data_type`] is not supported by
458    ///   the extension type ([`ExtensionType::supports_data_type`]))
459    pub fn try_extension_type<E: ExtensionType>(&self) -> Result<E, ArrowError> {
460        // Check the extension name in the metadata
461        match self.extension_type_name() {
462            // It should match the name of the given extension type
463            Some(name) if name == E::NAME => {
464                // Deserialize the metadata and try to construct the extension
465                // type
466                E::deserialize_metadata(self.extension_type_metadata())
467                    .and_then(|metadata| E::try_new(self.data_type(), metadata))
468            }
469            // Name mismatch
470            Some(name) => Err(ArrowError::InvalidArgumentError(format!(
471                "Field extension type name mismatch, expected {}, found {name}",
472                E::NAME
473            ))),
474            // Name missing
475            None => Err(ArrowError::InvalidArgumentError(
476                "Field extension type name missing".to_owned(),
477            )),
478        }
479    }
480
481    /// Returns an instance of the given [`ExtensionType`] of this [`Field`],
482    /// panics if this [`Field`] does not have this extension type.
483    ///
484    /// # Panic
485    ///
486    /// This calls [`Field::try_extension_type`] and panics when it returns an
487    /// error.
488    pub fn extension_type<E: ExtensionType>(&self) -> E {
489        self.try_extension_type::<E>()
490            .unwrap_or_else(|e| panic!("{e}"))
491    }
492
493    /// Updates the metadata of this [`Field`] with the [`ExtensionType::NAME`]
494    /// and [`ExtensionType::metadata`] of the given [`ExtensionType`], if the
495    /// given extension type supports the [`Field::data_type`] of this field
496    /// ([`ExtensionType::supports_data_type`]).
497    ///
498    /// If the given extension type defines no metadata, a previously set
499    /// value of [`EXTENSION_TYPE_METADATA_KEY`] is cleared.
500    ///
501    /// # Error
502    ///
503    /// This functions returns an error if the data type of this field does not
504    /// match any of the supported storage types of the given extension type.
505    pub fn try_with_extension_type<E: ExtensionType>(
506        &mut self,
507        extension_type: E,
508    ) -> Result<(), ArrowError> {
509        // Make sure the data type of this field is supported
510        extension_type.supports_data_type(&self.data_type)?;
511
512        self.metadata
513            .insert(EXTENSION_TYPE_NAME_KEY.to_owned(), E::NAME.to_owned());
514        match extension_type.serialize_metadata() {
515            Some(metadata) => self
516                .metadata
517                .insert(EXTENSION_TYPE_METADATA_KEY.to_owned(), metadata),
518            // If this extension type has no metadata, we make sure to
519            // clear previously set metadata.
520            None => self.metadata.remove(EXTENSION_TYPE_METADATA_KEY),
521        };
522
523        Ok(())
524    }
525
526    /// Updates the metadata of this [`Field`] with the [`ExtensionType::NAME`]
527    /// and [`ExtensionType::metadata`] of the given [`ExtensionType`].
528    ///
529    /// # Panics
530    ///
531    /// This calls [`Field::try_with_extension_type`] and panics when it
532    /// returns an error.
533    pub fn with_extension_type<E: ExtensionType>(mut self, extension_type: E) -> Self {
534        self.try_with_extension_type(extension_type)
535            .unwrap_or_else(|e| panic!("{e}"));
536        self
537    }
538
539    /// Returns the [`CanonicalExtensionType`] of this [`Field`], if set.
540    ///
541    /// # Error
542    ///
543    /// Returns an error if
544    /// - this field does have a canonical extension type (mismatch or missing)
545    /// - the canonical extension is not supported
546    /// - the construction of the extension type fails
547    #[cfg(feature = "canonical_extension_types")]
548    pub fn try_canonical_extension_type(&self) -> Result<CanonicalExtensionType, ArrowError> {
549        CanonicalExtensionType::try_from(self)
550    }
551
552    /// Indicates whether this [`Field`] supports null values.
553    ///
554    /// If true, the field *may* contain null values.
555    #[inline]
556    pub const fn is_nullable(&self) -> bool {
557        self.nullable
558    }
559
560    /// Set the `nullable` of this [`Field`].
561    ///
562    /// ```
563    /// # use arrow_schema::*;
564    /// let mut field = Field::new("c1", DataType::Int64, false);
565    /// field.set_nullable(true);
566    ///
567    /// assert_eq!(field.is_nullable(), true);
568    /// ```
569    #[inline]
570    pub fn set_nullable(&mut self, nullable: bool) {
571        self.nullable = nullable;
572    }
573
574    /// Set `nullable` of the [`Field`] and returns self.
575    ///
576    /// ```
577    /// # use arrow_schema::*;
578    /// let field = Field::new("c1", DataType::Int64, false)
579    ///    .with_nullable(true);
580    ///
581    /// assert_eq!(field.is_nullable(), true);
582    /// ```
583    pub fn with_nullable(mut self, nullable: bool) -> Self {
584        self.set_nullable(nullable);
585        self
586    }
587
588    /// Returns a (flattened) [`Vec`] containing all child [`Field`]s
589    /// within `self` contained within this field (including `self`)
590    pub(crate) fn fields(&self) -> Vec<&Field> {
591        let mut collected_fields = vec![self];
592        collected_fields.append(&mut Field::_fields(&self.data_type));
593
594        collected_fields
595    }
596
597    fn _fields(dt: &DataType) -> Vec<&Field> {
598        match dt {
599            DataType::Struct(fields) => fields.iter().flat_map(|f| f.fields()).collect(),
600            DataType::Union(fields, _) => fields.iter().flat_map(|(_, f)| f.fields()).collect(),
601            DataType::List(field)
602            | DataType::LargeList(field)
603            | DataType::FixedSizeList(field, _)
604            | DataType::Map(field, _) => field.fields(),
605            DataType::Dictionary(_, value_field) => Field::_fields(value_field.as_ref()),
606            DataType::RunEndEncoded(_, field) => field.fields(),
607            _ => vec![],
608        }
609    }
610
611    /// Returns a vector containing all (potentially nested) `Field` instances selected by the
612    /// dictionary ID they use
613    #[inline]
614    #[deprecated(
615        since = "54.0.0",
616        note = "The ability to preserve dictionary IDs will be removed. With it, all fields related to it."
617    )]
618    pub(crate) fn fields_with_dict_id(&self, id: i64) -> Vec<&Field> {
619        self.fields()
620            .into_iter()
621            .filter(|&field| {
622                #[allow(deprecated)]
623                let matching_dict_id = field.dict_id == id;
624                matches!(field.data_type(), DataType::Dictionary(_, _)) && matching_dict_id
625            })
626            .collect()
627    }
628
629    /// Returns the dictionary ID, if this is a dictionary type.
630    #[inline]
631    #[deprecated(
632        since = "54.0.0",
633        note = "The ability to preserve dictionary IDs will be removed. With it, all fields related to it."
634    )]
635    pub const fn dict_id(&self) -> Option<i64> {
636        match self.data_type {
637            #[allow(deprecated)]
638            DataType::Dictionary(_, _) => Some(self.dict_id),
639            _ => None,
640        }
641    }
642
643    /// Returns whether this `Field`'s dictionary is ordered, if this is a dictionary type.
644    ///
645    /// # Example
646    /// ```
647    /// # use arrow_schema::{DataType, Field};
648    /// // non dictionaries do not have a dict is ordered flat
649    /// let field = Field::new("c1", DataType::Int64, false);
650    /// assert_eq!(field.dict_is_ordered(), None);
651    /// // by default dictionary is not ordered
652    /// let field = Field::new("c1", DataType::Dictionary(Box::new(DataType::Int64), Box::new(DataType::Utf8)), false);
653    /// assert_eq!(field.dict_is_ordered(), Some(false));
654    /// let field = field.with_dict_is_ordered(true);
655    /// assert_eq!(field.dict_is_ordered(), Some(true));
656    /// ```
657    #[inline]
658    pub const fn dict_is_ordered(&self) -> Option<bool> {
659        match self.data_type {
660            DataType::Dictionary(_, _) => Some(self.dict_is_ordered),
661            _ => None,
662        }
663    }
664
665    /// Set the is ordered field for this `Field`, if it is a dictionary.
666    ///
667    /// Does nothing if this is not a dictionary type.
668    ///
669    /// See [`Field::dict_is_ordered`] for more information.
670    pub fn with_dict_is_ordered(mut self, dict_is_ordered: bool) -> Self {
671        if matches!(self.data_type, DataType::Dictionary(_, _)) {
672            self.dict_is_ordered = dict_is_ordered;
673        };
674        self
675    }
676
677    /// Merge this field into self if it is compatible.
678    ///
679    /// Struct fields are merged recursively.
680    ///
681    /// NOTE: `self` may be updated to a partial / unexpected state in case of merge failure.
682    ///
683    /// Example:
684    ///
685    /// ```
686    /// # use arrow_schema::*;
687    /// let mut field = Field::new("c1", DataType::Int64, false);
688    /// assert!(field.try_merge(&Field::new("c1", DataType::Int64, true)).is_ok());
689    /// assert!(field.is_nullable());
690    /// ```
691    pub fn try_merge(&mut self, from: &Field) -> Result<(), ArrowError> {
692        #[allow(deprecated)]
693        if from.dict_id != self.dict_id {
694            return Err(ArrowError::SchemaError(format!(
695                "Fail to merge schema field '{}' because from dict_id = {} does not match {}",
696                self.name, from.dict_id, self.dict_id
697            )));
698        }
699        if from.dict_is_ordered != self.dict_is_ordered {
700            return Err(ArrowError::SchemaError(format!(
701                "Fail to merge schema field '{}' because from dict_is_ordered = {} does not match {}",
702                self.name, from.dict_is_ordered, self.dict_is_ordered
703            )));
704        }
705        // merge metadata
706        match (self.metadata().is_empty(), from.metadata().is_empty()) {
707            (false, false) => {
708                let mut merged = self.metadata().clone();
709                for (key, from_value) in from.metadata() {
710                    if let Some(self_value) = self.metadata.get(key) {
711                        if self_value != from_value {
712                            return Err(ArrowError::SchemaError(format!(
713                                "Fail to merge field '{}' due to conflicting metadata data value for key {}.
714                                    From value = {} does not match {}", self.name, key, from_value, self_value),
715                            ));
716                        }
717                    } else {
718                        merged.insert(key.clone(), from_value.clone());
719                    }
720                }
721                self.set_metadata(merged);
722            }
723            (true, false) => {
724                self.set_metadata(from.metadata().clone());
725            }
726            _ => {}
727        }
728        match &mut self.data_type {
729            DataType::Struct(nested_fields) => match &from.data_type {
730                DataType::Struct(from_nested_fields) => {
731                    let mut builder = SchemaBuilder::new();
732                    nested_fields.iter().chain(from_nested_fields).try_for_each(|f| builder.try_merge(f))?;
733                    *nested_fields = builder.finish().fields;
734                }
735                _ => {
736                    return Err(ArrowError::SchemaError(
737                        format!("Fail to merge schema field '{}' because the from data_type = {} is not DataType::Struct",
738                            self.name, from.data_type)
739                ))}
740            },
741            DataType::Union(nested_fields, _) => match &from.data_type {
742                DataType::Union(from_nested_fields, _) => {
743                    nested_fields.try_merge(from_nested_fields)?
744                }
745                _ => {
746                    return Err(ArrowError::SchemaError(
747                        format!("Fail to merge schema field '{}' because the from data_type = {} is not DataType::Union",
748                            self.name, from.data_type)
749                    ));
750                }
751            },
752            DataType::List(field) => match &from.data_type {
753                DataType::List(from_field) => {
754                    let mut f = (**field).clone();
755                    f.try_merge(from_field)?;
756                    (*field) = Arc::new(f);
757                },
758                _ => {
759                    return Err(ArrowError::SchemaError(
760                        format!("Fail to merge schema field '{}' because the from data_type = {} is not DataType::List",
761                            self.name, from.data_type)
762                ))}
763            },
764            DataType::LargeList(field) => match &from.data_type {
765                DataType::LargeList(from_field) => {
766                    let mut f = (**field).clone();
767                    f.try_merge(from_field)?;
768                    (*field) = Arc::new(f);
769                },
770                _ => {
771                    return Err(ArrowError::SchemaError(
772                        format!("Fail to merge schema field '{}' because the from data_type = {} is not DataType::LargeList",
773                            self.name, from.data_type)
774                ))}
775            },
776            DataType::Null => {
777                self.nullable = true;
778                self.data_type = from.data_type.clone();
779            }
780            | DataType::Boolean
781            | DataType::Int8
782            | DataType::Int16
783            | DataType::Int32
784            | DataType::Int64
785            | DataType::UInt8
786            | DataType::UInt16
787            | DataType::UInt32
788            | DataType::UInt64
789            | DataType::Float16
790            | DataType::Float32
791            | DataType::Float64
792            | DataType::Timestamp(_, _)
793            | DataType::Date32
794            | DataType::Date64
795            | DataType::Time32(_)
796            | DataType::Time64(_)
797            | DataType::Duration(_)
798            | DataType::Binary
799            | DataType::LargeBinary
800            | DataType::BinaryView
801            | DataType::Interval(_)
802            | DataType::LargeListView(_)
803            | DataType::ListView(_)
804            | DataType::Map(_, _)
805            | DataType::Dictionary(_, _)
806            | DataType::RunEndEncoded(_, _)
807            | DataType::FixedSizeList(_, _)
808            | DataType::FixedSizeBinary(_)
809            | DataType::Utf8
810            | DataType::LargeUtf8
811            | DataType::Utf8View
812            | DataType::Decimal128(_, _)
813            | DataType::Decimal256(_, _) => {
814                if from.data_type == DataType::Null {
815                    self.nullable = true;
816                } else if self.data_type != from.data_type {
817                    return Err(ArrowError::SchemaError(
818                        format!("Fail to merge schema field '{}' because the from data_type = {} does not equal {}",
819                            self.name, from.data_type, self.data_type)
820                    ));
821                }
822            }
823        }
824        self.nullable |= from.nullable;
825
826        Ok(())
827    }
828
829    /// Check to see if `self` is a superset of `other` field. Superset is defined as:
830    ///
831    /// * if nullability doesn't match, self needs to be nullable
832    /// * self.metadata is a superset of other.metadata
833    /// * all other fields are equal
834    pub fn contains(&self, other: &Field) -> bool {
835        #[allow(deprecated)]
836        let matching_dict_id = self.dict_id == other.dict_id;
837        self.name == other.name
838        && self.data_type.contains(&other.data_type)
839        && matching_dict_id
840        && self.dict_is_ordered == other.dict_is_ordered
841        // self need to be nullable or both of them are not nullable
842        && (self.nullable || !other.nullable)
843        // make sure self.metadata is a superset of other.metadata
844        && other.metadata.iter().all(|(k, v1)| {
845            self.metadata.get(k).map(|v2| v1 == v2).unwrap_or_default()
846        })
847    }
848
849    /// Return size of this instance in bytes.
850    ///
851    /// Includes the size of `Self`.
852    pub fn size(&self) -> usize {
853        std::mem::size_of_val(self) - std::mem::size_of_val(&self.data_type)
854            + self.data_type.size()
855            + self.name.capacity()
856            + (std::mem::size_of::<(String, String)>() * self.metadata.capacity())
857            + self
858                .metadata
859                .iter()
860                .map(|(k, v)| k.capacity() + v.capacity())
861                .sum::<usize>()
862    }
863}
864
865// TODO: improve display with crate https://crates.io/crates/derive_more ?
866impl std::fmt::Display for Field {
867    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
868        write!(f, "{self:?}")
869    }
870}
871
872#[cfg(test)]
873mod test {
874    use super::*;
875    use std::collections::hash_map::DefaultHasher;
876
877    #[test]
878    fn test_new_with_string() {
879        // Fields should allow owned Strings to support reuse
880        let s = "c1";
881        Field::new(s, DataType::Int64, false);
882    }
883
884    #[test]
885    fn test_new_dict_with_string() {
886        // Fields should allow owned Strings to support reuse
887        let s = "c1";
888        #[allow(deprecated)]
889        Field::new_dict(s, DataType::Int64, false, 4, false);
890    }
891
892    #[test]
893    fn test_merge_incompatible_types() {
894        let mut field = Field::new("c1", DataType::Int64, false);
895        let result = field
896            .try_merge(&Field::new("c1", DataType::Float32, true))
897            .expect_err("should fail")
898            .to_string();
899        assert_eq!("Schema error: Fail to merge schema field 'c1' because the from data_type = Float32 does not equal Int64", result);
900    }
901
902    #[test]
903    fn test_merge_with_null() {
904        let mut field1 = Field::new("c1", DataType::Null, true);
905        field1
906            .try_merge(&Field::new("c1", DataType::Float32, false))
907            .expect("should widen type to nullable float");
908        assert_eq!(Field::new("c1", DataType::Float32, true), field1);
909
910        let mut field2 = Field::new("c2", DataType::Utf8, false);
911        field2
912            .try_merge(&Field::new("c2", DataType::Null, true))
913            .expect("should widen type to nullable utf8");
914        assert_eq!(Field::new("c2", DataType::Utf8, true), field2);
915    }
916
917    #[test]
918    fn test_merge_with_nested_null() {
919        let mut struct1 = Field::new(
920            "s1",
921            DataType::Struct(Fields::from(vec![Field::new(
922                "inner",
923                DataType::Float32,
924                false,
925            )])),
926            false,
927        );
928
929        let struct2 = Field::new(
930            "s2",
931            DataType::Struct(Fields::from(vec![Field::new(
932                "inner",
933                DataType::Null,
934                false,
935            )])),
936            true,
937        );
938
939        struct1
940            .try_merge(&struct2)
941            .expect("should widen inner field's type to nullable float");
942        assert_eq!(
943            Field::new(
944                "s1",
945                DataType::Struct(Fields::from(vec![Field::new(
946                    "inner",
947                    DataType::Float32,
948                    true,
949                )])),
950                true,
951            ),
952            struct1
953        );
954
955        let mut list1 = Field::new(
956            "l1",
957            DataType::List(Field::new("inner", DataType::Float32, false).into()),
958            false,
959        );
960
961        let list2 = Field::new(
962            "l2",
963            DataType::List(Field::new("inner", DataType::Null, false).into()),
964            true,
965        );
966
967        list1
968            .try_merge(&list2)
969            .expect("should widen inner field's type to nullable float");
970        assert_eq!(
971            Field::new(
972                "l1",
973                DataType::List(Field::new("inner", DataType::Float32, true).into()),
974                true,
975            ),
976            list1
977        );
978
979        let mut large_list1 = Field::new(
980            "ll1",
981            DataType::LargeList(Field::new("inner", DataType::Float32, false).into()),
982            false,
983        );
984
985        let large_list2 = Field::new(
986            "ll2",
987            DataType::LargeList(Field::new("inner", DataType::Null, false).into()),
988            true,
989        );
990
991        large_list1
992            .try_merge(&large_list2)
993            .expect("should widen inner field's type to nullable float");
994        assert_eq!(
995            Field::new(
996                "ll1",
997                DataType::LargeList(Field::new("inner", DataType::Float32, true).into()),
998                true,
999            ),
1000            large_list1
1001        );
1002    }
1003
1004    #[test]
1005    fn test_fields_with_dict_id() {
1006        #[allow(deprecated)]
1007        let dict1 = Field::new_dict(
1008            "dict1",
1009            DataType::Dictionary(DataType::Utf8.into(), DataType::Int32.into()),
1010            false,
1011            10,
1012            false,
1013        );
1014        #[allow(deprecated)]
1015        let dict2 = Field::new_dict(
1016            "dict2",
1017            DataType::Dictionary(DataType::Int32.into(), DataType::Int8.into()),
1018            false,
1019            20,
1020            false,
1021        );
1022
1023        let field = Field::new(
1024            "struct<dict1, list[struct<dict2, list[struct<dict1]>]>",
1025            DataType::Struct(Fields::from(vec![
1026                dict1.clone(),
1027                Field::new(
1028                    "list[struct<dict1, list[struct<dict2>]>]",
1029                    DataType::List(Arc::new(Field::new(
1030                        "struct<dict1, list[struct<dict2>]>",
1031                        DataType::Struct(Fields::from(vec![
1032                            dict1.clone(),
1033                            Field::new(
1034                                "list[struct<dict2>]",
1035                                DataType::List(Arc::new(Field::new(
1036                                    "struct<dict2>",
1037                                    DataType::Struct(vec![dict2.clone()].into()),
1038                                    false,
1039                                ))),
1040                                false,
1041                            ),
1042                        ])),
1043                        false,
1044                    ))),
1045                    false,
1046                ),
1047            ])),
1048            false,
1049        );
1050
1051        #[allow(deprecated)]
1052        for field in field.fields_with_dict_id(10) {
1053            assert_eq!(dict1, *field);
1054        }
1055        #[allow(deprecated)]
1056        for field in field.fields_with_dict_id(20) {
1057            assert_eq!(dict2, *field);
1058        }
1059    }
1060
1061    fn get_field_hash(field: &Field) -> u64 {
1062        let mut s = DefaultHasher::new();
1063        field.hash(&mut s);
1064        s.finish()
1065    }
1066
1067    #[test]
1068    fn test_field_comparison_case() {
1069        // dictionary-encoding properties not used for field comparison
1070        #[allow(deprecated)]
1071        let dict1 = Field::new_dict(
1072            "dict1",
1073            DataType::Dictionary(DataType::Utf8.into(), DataType::Int32.into()),
1074            false,
1075            10,
1076            false,
1077        );
1078        #[allow(deprecated)]
1079        let dict2 = Field::new_dict(
1080            "dict1",
1081            DataType::Dictionary(DataType::Utf8.into(), DataType::Int32.into()),
1082            false,
1083            20,
1084            false,
1085        );
1086
1087        assert_eq!(dict1, dict2);
1088        assert_eq!(get_field_hash(&dict1), get_field_hash(&dict2));
1089
1090        #[allow(deprecated)]
1091        let dict1 = Field::new_dict(
1092            "dict0",
1093            DataType::Dictionary(DataType::Utf8.into(), DataType::Int32.into()),
1094            false,
1095            10,
1096            false,
1097        );
1098
1099        assert_ne!(dict1, dict2);
1100        assert_ne!(get_field_hash(&dict1), get_field_hash(&dict2));
1101    }
1102
1103    #[test]
1104    fn test_field_comparison_metadata() {
1105        let f1 = Field::new("x", DataType::Binary, false).with_metadata(HashMap::from([
1106            (String::from("k1"), String::from("v1")),
1107            (String::from("k2"), String::from("v2")),
1108        ]));
1109        let f2 = Field::new("x", DataType::Binary, false).with_metadata(HashMap::from([
1110            (String::from("k1"), String::from("v1")),
1111            (String::from("k3"), String::from("v3")),
1112        ]));
1113        let f3 = Field::new("x", DataType::Binary, false).with_metadata(HashMap::from([
1114            (String::from("k1"), String::from("v1")),
1115            (String::from("k3"), String::from("v4")),
1116        ]));
1117
1118        assert!(f1.cmp(&f2).is_lt());
1119        assert!(f2.cmp(&f3).is_lt());
1120        assert!(f1.cmp(&f3).is_lt());
1121    }
1122
1123    #[test]
1124    fn test_contains_reflexivity() {
1125        let mut field = Field::new("field1", DataType::Float16, false);
1126        field.set_metadata(HashMap::from([
1127            (String::from("k0"), String::from("v0")),
1128            (String::from("k1"), String::from("v1")),
1129        ]));
1130        assert!(field.contains(&field))
1131    }
1132
1133    #[test]
1134    fn test_contains_transitivity() {
1135        let child_field = Field::new("child1", DataType::Float16, false);
1136
1137        let mut field1 = Field::new(
1138            "field1",
1139            DataType::Struct(Fields::from(vec![child_field])),
1140            false,
1141        );
1142        field1.set_metadata(HashMap::from([(String::from("k1"), String::from("v1"))]));
1143
1144        let mut field2 = Field::new("field1", DataType::Struct(Fields::default()), true);
1145        field2.set_metadata(HashMap::from([(String::from("k2"), String::from("v2"))]));
1146        field2.try_merge(&field1).unwrap();
1147
1148        let mut field3 = Field::new("field1", DataType::Struct(Fields::default()), false);
1149        field3.set_metadata(HashMap::from([(String::from("k3"), String::from("v3"))]));
1150        field3.try_merge(&field2).unwrap();
1151
1152        assert!(field2.contains(&field1));
1153        assert!(field3.contains(&field2));
1154        assert!(field3.contains(&field1));
1155
1156        assert!(!field1.contains(&field2));
1157        assert!(!field1.contains(&field3));
1158        assert!(!field2.contains(&field3));
1159    }
1160
1161    #[test]
1162    fn test_contains_nullable() {
1163        let field1 = Field::new("field1", DataType::Boolean, true);
1164        let field2 = Field::new("field1", DataType::Boolean, false);
1165        assert!(field1.contains(&field2));
1166        assert!(!field2.contains(&field1));
1167    }
1168
1169    #[test]
1170    fn test_contains_must_have_same_fields() {
1171        let child_field1 = Field::new("child1", DataType::Float16, false);
1172        let child_field2 = Field::new("child2", DataType::Float16, false);
1173
1174        let field1 = Field::new(
1175            "field1",
1176            DataType::Struct(vec![child_field1.clone()].into()),
1177            true,
1178        );
1179        let field2 = Field::new(
1180            "field1",
1181            DataType::Struct(vec![child_field1, child_field2].into()),
1182            true,
1183        );
1184
1185        assert!(!field1.contains(&field2));
1186        assert!(!field2.contains(&field1));
1187
1188        // UnionFields with different type ID
1189        let field1 = Field::new(
1190            "field1",
1191            DataType::Union(
1192                UnionFields::new(
1193                    vec![1, 2],
1194                    vec![
1195                        Field::new("field1", DataType::UInt8, true),
1196                        Field::new("field3", DataType::Utf8, false),
1197                    ],
1198                ),
1199                UnionMode::Dense,
1200            ),
1201            true,
1202        );
1203        let field2 = Field::new(
1204            "field1",
1205            DataType::Union(
1206                UnionFields::new(
1207                    vec![1, 3],
1208                    vec![
1209                        Field::new("field1", DataType::UInt8, false),
1210                        Field::new("field3", DataType::Utf8, false),
1211                    ],
1212                ),
1213                UnionMode::Dense,
1214            ),
1215            true,
1216        );
1217        assert!(!field1.contains(&field2));
1218
1219        // UnionFields with same type ID
1220        let field1 = Field::new(
1221            "field1",
1222            DataType::Union(
1223                UnionFields::new(
1224                    vec![1, 2],
1225                    vec![
1226                        Field::new("field1", DataType::UInt8, true),
1227                        Field::new("field3", DataType::Utf8, false),
1228                    ],
1229                ),
1230                UnionMode::Dense,
1231            ),
1232            true,
1233        );
1234        let field2 = Field::new(
1235            "field1",
1236            DataType::Union(
1237                UnionFields::new(
1238                    vec![1, 2],
1239                    vec![
1240                        Field::new("field1", DataType::UInt8, false),
1241                        Field::new("field3", DataType::Utf8, false),
1242                    ],
1243                ),
1244                UnionMode::Dense,
1245            ),
1246            true,
1247        );
1248        assert!(field1.contains(&field2));
1249    }
1250
1251    #[cfg(feature = "serde")]
1252    fn assert_binary_serde_round_trip(field: Field) {
1253        let serialized = bincode::serialize(&field).unwrap();
1254        let deserialized: Field = bincode::deserialize(&serialized).unwrap();
1255        assert_eq!(field, deserialized)
1256    }
1257
1258    #[cfg(feature = "serde")]
1259    #[test]
1260    fn test_field_without_metadata_serde() {
1261        let field = Field::new("name", DataType::Boolean, true);
1262        assert_binary_serde_round_trip(field)
1263    }
1264
1265    #[cfg(feature = "serde")]
1266    #[test]
1267    fn test_field_with_empty_metadata_serde() {
1268        let field = Field::new("name", DataType::Boolean, false).with_metadata(HashMap::new());
1269
1270        assert_binary_serde_round_trip(field)
1271    }
1272
1273    #[cfg(feature = "serde")]
1274    #[test]
1275    fn test_field_with_nonempty_metadata_serde() {
1276        let mut metadata = HashMap::new();
1277        metadata.insert("hi".to_owned(), "".to_owned());
1278        let field = Field::new("name", DataType::Boolean, false).with_metadata(metadata);
1279
1280        assert_binary_serde_round_trip(field)
1281    }
1282}
arrow_schema/field.rs

arrow_schema/
field.rs
