Add ability to compare/sort/merge items using a sortby config #856
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gadomski
reviewed
Nov 20, 2025
gadomski
reviewed
Nov 21, 2025
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| impl Default for ItemComparator { | ||
| /// Creates a new `ItemComparator` with the default sort order. | ||
| /// | ||
| /// The default sort order is `datetime` descending, followed by `id` ascending. | ||
| fn default() -> Self { | ||
| Self { | ||
| sort_fields: vec![ | ||
| SortField { | ||
| field: "datetime".to_string(), | ||
| direction: Direction::Desc, | ||
| }, | ||
| SortField { | ||
| field: "id".to_string(), | ||
| direction: Direction::Asc, | ||
| }, | ||
| ], | ||
| } | ||
| } | ||
| } |
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The existance of this default implementation implies (I think) that we could impl PartialOrd for Item?
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| /// Sorts multiple streams of items into a single sorted stream. | ||
| /// | ||
| /// # Examples | ||
| /// | ||
| /// ``` | ||
| /// use stac::{Item, sort::sort_streams}; | ||
| /// use serde_json::json; | ||
| /// use futures::stream::{self, StreamExt}; | ||
| /// | ||
| /// # tokio_test::block_on(async { | ||
| /// let stream1 = stream::iter(vec![Item::new("a"), Item::new("c")]); | ||
| /// let stream2 = stream::iter(vec![Item::new("b"), Item::new("d")]); | ||
| /// let config = json!({ | ||
| /// "sortby": [ | ||
| /// { "field": "id", "direction": "asc" } | ||
| /// ] | ||
| /// }); | ||
| /// let mut sorted = sort_streams(vec![stream1, stream2], config).unwrap(); | ||
| /// assert_eq!(sorted.next().await.unwrap().id, "a"); | ||
| /// assert_eq!(sorted.next().await.unwrap().id, "b"); | ||
| /// assert_eq!(sorted.next().await.unwrap().id, "c"); | ||
| /// assert_eq!(sorted.next().await.unwrap().id, "d"); | ||
| /// # }); | ||
| /// ``` | ||
| pub fn sort_streams<S, I>( | ||
| streams: I, | ||
| config: Value, | ||
| ) -> Result<impl Stream<Item = S::Item>, serde_json::Error> | ||
| where | ||
| S: Stream<Item = Item> + Unpin, | ||
| I: IntoIterator<Item = S>, | ||
| { | ||
| let comparator = ItemComparator::new(config)?; | ||
| Ok(kmerge_by(streams, move |a, b| { | ||
| comparator.compare(a, b).reverse() | ||
| })) | ||
| } |
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What's the use-case for the stream merging?
| @@ -0,0 +1,541 @@ | |||
| use crate::Item; | |||
| use futures::Stream; | |||
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I don't think we should be bringing in any async stuff into this crate, unless we really need to. What's the use-case for this?
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Description
Creates an ItemComparator that implements compare.Compare that can be built using a json sortby config.
This can be used to compare items (returning Ordering) or to sort an array of items.
There is also a function that can be used to merge and interleave multiple streams of sorted items with this config (with an eye towards federated search or similar processing of multiple streams of items).
Checklist
Delete any checklist items that do not apply (e.g. if your change is minor, it may not require documentation updates).
cargo fmt)cargo test