src/api/helpers.rs

@@ -137,6 +137,32 @@ pub fn parse_bucket_key<'a>(
 	Ok((bucket, key))
 }
 
+const UTF8_BEFORE_LAST_CHAR: char = '\u{10FFFE}';
+
+/// Compute the key after the prefix
+pub fn key_after_prefix(pfx: &str) -> Option<String> {
+	let mut next = pfx.to_string();
+	while !next.is_empty() {
+		let tail = next.pop().unwrap();
+		if tail >= char::MAX {
+			continue;
+		}
+
+		// Circumvent a limitation of RangeFrom that overflow earlier than needed
+		// See: https://doc.rust-lang.org/core/ops/struct.RangeFrom.html
+		let new_tail = if tail == UTF8_BEFORE_LAST_CHAR {
+			char::MAX
+		} else {
+			(tail..).nth(1).unwrap()
+		};
+
+		next.push(new_tail);
+		return Some(next);
+	}
+
+	None
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;
@@ -236,4 +262,37 @@ mod tests {
 		assert_eq!(host_to_bucket("not-garage.tld", "garage.tld"), None);
 		assert_eq!(host_to_bucket("not-garage.tld", ".garage.tld"), None);
 	}
+
+	#[test]
+	fn test_key_after_prefix() {
+		assert_eq!(UTF8_BEFORE_LAST_CHAR as u32, (char::MAX as u32) - 1);
+		assert_eq!(key_after_prefix("a/b/").unwrap().as_str(), "a/b0");
+		assert_eq!(key_after_prefix("€").unwrap().as_str(), "₭");
+		assert_eq!(
+			key_after_prefix("􏿽").unwrap().as_str(),
+			String::from(char::from_u32(0x10FFFE).unwrap())
+		);
+
+		// When the last character is the biggest UTF8 char
+		let a = String::from_iter(['a', char::MAX].iter());
+		assert_eq!(key_after_prefix(a.as_str()).unwrap().as_str(), "b");
+
+		// When all characters are the biggest UTF8 char
+		let b = String::from_iter([char::MAX; 3].iter());
+		assert!(key_after_prefix(b.as_str()).is_none());
+
+		// Check utf8 surrogates
+		let c = String::from('\u{D7FF}');
+		assert_eq!(
+			key_after_prefix(c.as_str()).unwrap().as_str(),
+			String::from('\u{E000}')
+		);
+
+		// Check the character before the biggest one
+		let d = String::from('\u{10FFFE}');
+		assert_eq!(
+			key_after_prefix(d.as_str()).unwrap().as_str(),
+			String::from(char::MAX)
+		);
+	}
 }

src/api/k2v/batch.rs

@@ -90,8 +90,8 @@ async fn handle_read_batch_query(
 	};
 
 	let (items, more, next_start) = if query.single_item {
-		if query.prefix.is_some() || query.end.is_some() || query.limit.is_some() {
+		if query.prefix.is_some() || query.end.is_some() || query.limit.is_some() || query.reverse {
-			return Err(Error::BadRequest("Batch query parameters 'prefix', 'end' and 'limit' must not be set when singleItem is true.".into()));
+			return Err(Error::BadRequest("Batch query parameters 'prefix', 'end', 'limit' and 'reverse' must not be set when singleItem is true.".into()));
 		}
 		let sk = query
 			.start

src/api/k2v/range.rs

@@ -8,6 +8,7 @@ use garage_table::replication::TableShardedReplication;
 use garage_table::*;
 
 use crate::error::*;
+use crate::helpers::key_after_prefix;
 
 /// Read range in a Garage table.
 /// Returns (entries, more?, nextStart)
@@ -25,10 +26,9 @@ pub(crate) async fn read_range<F>(
 where
 	F: TableSchema<S = String> + 'static,
 {
-	let mut start = match (prefix, start) {
+	let (mut start, mut start_ignore) = match (prefix, start) {
-		(None, None) => "".to_string(),
+		(None, None) => (None, false),
-		(Some(p), None) => p.clone(),
+		(None, Some(s)) => (Some(s.clone()), false),
-		(None, Some(s)) => s.clone(),
 		(Some(p), Some(s)) => {
 			if !s.starts_with(p) {
 				return Err(Error::BadRequest(format!(
@@ -36,10 +36,15 @@ where
 					s, p
 				)));
 			}
-			s.clone()
+			(Some(s.clone()), false)
 		}
+		(Some(p), None) if enumeration_order == EnumerationOrder::Reverse => {
+			let start = key_after_prefix(p)
+				.ok_or_internal_error("Sorry, can't list this prefix in reverse order")?;
+			(Some(start), true)
+		}
+		(Some(p), None) => (Some(p.clone()), false),
 	};
-	let mut start_ignore = false;
 
 	let mut entries = vec![];
 	loop {
@@ -50,7 +55,7 @@ where
 		let get_ret = table
 			.get_range(
 				partition_key,
-				Some(start.clone()),
+				start.clone(),
 				filter.clone(),
 				n_get,
 				enumeration_order,
@@ -60,6 +65,9 @@ where
 		let get_ret_len = get_ret.len();
 
 		for entry in get_ret {
+			if start_ignore && Some(entry.sort_key()) == start.as_ref() {
+				continue;
+			}
 			if let Some(p) = prefix {
 				if !entry.sort_key().starts_with(p) {
 					return Ok((entries, false, None));
@@ -75,9 +83,6 @@ where
 					return Ok((entries, true, Some(entry.sort_key().clone())));
 				}
 			}
-			if start_ignore && entry.sort_key() == &start {
-				continue;
-			}
 			entries.push(entry);
 		}
 
@@ -85,7 +90,7 @@ where
 			return Ok((entries, false, None));
 		}
 
-		start = entries.last().unwrap().sort_key().clone();
+		start = Some(entries.last().unwrap().sort_key().clone());
 		start_ignore = true;
 	}
 }

src/api/s3/list.rs

@@ -17,6 +17,7 @@ use garage_table::{EmptyKey, EnumerationOrder};
 
 use crate::encoding::*;
 use crate::error::*;
+use crate::helpers::key_after_prefix;
 use crate::s3::put as s3_put;
 use crate::s3::xml as s3_xml;
 
@@ -935,32 +936,6 @@ fn uriencode_maybe(s: &str, yes: bool) -> s3_xml::Value {
 	}
 }
 
-const UTF8_BEFORE_LAST_CHAR: char = '\u{10FFFE}';
-
-/// Compute the key after the prefix
-fn key_after_prefix(pfx: &str) -> Option<String> {
-	let mut next = pfx.to_string();
-	while !next.is_empty() {
-		let tail = next.pop().unwrap();
-		if tail >= char::MAX {
-			continue;
-		}
-
-		// Circumvent a limitation of RangeFrom that overflow earlier than needed
-		// See: https://doc.rust-lang.org/core/ops/struct.RangeFrom.html
-		let new_tail = if tail == UTF8_BEFORE_LAST_CHAR {
-			char::MAX
-		} else {
-			(tail..).nth(1).unwrap()
-		};
-
-		next.push(new_tail);
-		return Some(next);
-	}
-
-	None
-}
-
 /*
  * Unit tests of this module
  */
@@ -1014,39 +989,6 @@ mod tests {
 		}
 	}
 
-	#[test]
-	fn test_key_after_prefix() {
-		assert_eq!(UTF8_BEFORE_LAST_CHAR as u32, (char::MAX as u32) - 1);
-		assert_eq!(key_after_prefix("a/b/").unwrap().as_str(), "a/b0");
-		assert_eq!(key_after_prefix("€").unwrap().as_str(), "₭");
-		assert_eq!(
-			key_after_prefix("􏿽").unwrap().as_str(),
-			String::from(char::from_u32(0x10FFFE).unwrap())
-		);
-
-		// When the last character is the biggest UTF8 char
-		let a = String::from_iter(['a', char::MAX].iter());
-		assert_eq!(key_after_prefix(a.as_str()).unwrap().as_str(), "b");
-
-		// When all characters are the biggest UTF8 char
-		let b = String::from_iter([char::MAX; 3].iter());
-		assert!(key_after_prefix(b.as_str()).is_none());
-
-		// Check utf8 surrogates
-		let c = String::from('\u{D7FF}');
-		assert_eq!(
-			key_after_prefix(c.as_str()).unwrap().as_str(),
-			String::from('\u{E000}')
-		);
-
-		// Check the character before the biggest one
-		let d = String::from('\u{10FFFE}');
-		assert_eq!(
-			key_after_prefix(d.as_str()).unwrap().as_str(),
-			String::from(char::MAX)
-		);
-	}
-
 	#[test]
 	fn test_common_prefixes() {
 		let mut query = query();

src/garage/tests/k2v/batch.rs

@@ -92,6 +92,7 @@ async fn test_batch() {
 			br#"[
 	{"partitionKey": "root"},
 	{"partitionKey": "root", "start": "c"},
+	{"partitionKey": "root", "start": "c", "reverse": true, "end": "a"},
 	{"partitionKey": "root", "limit": 1},
 	{"partitionKey": "root", "prefix": "d"}
 		]"#
@@ -146,6 +147,23 @@ async fn test_batch() {
 				"more": false,
 				"nextStart": null,
 			},
+			{
+				"partitionKey": "root",
+				"prefix": null,
+				"start": "c",
+				"end": "a",
+				"limit": null,
+				"reverse": true,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "c", "ct": ct.get("c").unwrap(), "v": [base64::encode(values.get("c").unwrap())]},
+				  {"sk": "b", "ct": ct.get("b").unwrap(), "v": [base64::encode(values.get("b").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
 			{
 				"partitionKey": "root",
 				"prefix": null,
@@ -252,6 +270,8 @@ async fn test_batch() {
 	{"partitionKey": "root", "prefix": "d.", "end": "d.2"},
 	{"partitionKey": "root", "prefix": "d.", "limit": 1},
 	{"partitionKey": "root", "prefix": "d.", "start": "d.2", "limit": 1},
+	{"partitionKey": "root", "prefix": "d.", "reverse": true},
+	{"partitionKey": "root", "prefix": "d.", "start": "d.2", "reverse": true},
 	{"partitionKey": "root", "prefix": "d.", "limit": 2}
 		]"#
 			.to_vec(),
@@ -350,6 +370,40 @@ async fn test_batch() {
 				"more": false,
 				"nextStart": null,
 			},
+			{
+				"partitionKey": "root",
+				"prefix": "d.",
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": true,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "d.2", "ct": ct.get("d.2").unwrap(), "v": [base64::encode(values.get("d.2").unwrap()), base64::encode(values.get("d.2'").unwrap())]},
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1'").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
+			{
+				"partitionKey": "root",
+				"prefix": "d.",
+				"start": "d.2",
+				"end": null,
+				"limit": null,
+				"reverse": true,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "d.2", "ct": ct.get("d.2").unwrap(), "v": [base64::encode(values.get("d.2").unwrap()), base64::encode(values.get("d.2'").unwrap())]},
+				  {"sk": "d.1", "ct": ct.get("d.1").unwrap(), "v": [base64::encode(values.get("d.1'").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
 			{
 				"partitionKey": "root",
 				"prefix": "d.",
@@ -418,7 +472,8 @@ async fn test_batch() {
 		.query_param("search", Option::<&str>::None)
 		.body(
 			br#"[
-	{"partitionKey": "root"}
+	{"partitionKey": "root"},
+	{"partitionKey": "root", "reverse": true}
 		]"#
 			.to_vec(),
 		)
@@ -448,6 +503,23 @@ async fn test_batch() {
 				"more": false,
 				"nextStart": null,
 			},
+			{
+				"partitionKey": "root",
+				"prefix": null,
+				"start": null,
+				"end": null,
+				"limit": null,
+				"reverse": true,
+				"conflictsOnly": false,
+				"tombstones": false,
+				"singleItem": false,
+				"items": [
+				  {"sk": "e", "ct": ct.get("e").unwrap(), "v": [base64::encode(values.get("e").unwrap())]},
+				  {"sk": "c", "ct": ct.get("c").unwrap(), "v": [base64::encode(values.get("c").unwrap()), base64::encode(values.get("c'").unwrap())]},
+				],
+				"more": false,
+				"nextStart": null,
+			},
 		])
 	);
 }

src/table/data.rs

@@ -1,4 +1,5 @@
 use core::borrow::Borrow;
+use std::convert::TryInto;
 use std::sync::Arc;
 
 use serde_bytes::ByteBuf;
@@ -84,26 +85,36 @@ where
 
 	pub fn read_range(
 		&self,
-		p: &F::P,
+		partition_key: &F::P,
-		s: &Option<F::S>,
+		start: &Option<F::S>,
 		filter: &Option<F::Filter>,
 		limit: usize,
 		enumeration_order: EnumerationOrder,
 	) -> Result<Vec<Arc<ByteBuf>>, Error> {
-		let partition_hash = p.hash();
+		let partition_hash = partition_key.hash();
-		let first_key = match s {
-			None => partition_hash.to_vec(),
-			Some(sk) => self.tree_key(p, sk),
-		};
 		match enumeration_order {
 			EnumerationOrder::Forward => {
+				let first_key = match start {
+					None => partition_hash.to_vec(),
+					Some(sk) => self.tree_key(partition_key, sk),
+				};
 				let range = self.store.range(first_key..);
 				self.read_range_aux(partition_hash, range, filter, limit)
 			}
-			EnumerationOrder::Reverse => {
+			EnumerationOrder::Reverse => match start {
-				let range = self.store.range(..=first_key).rev();
+				Some(sk) => {
-				self.read_range_aux(partition_hash, range, filter, limit)
+					let last_key = self.tree_key(partition_key, sk);
-			}
+					let range = self.store.range(..=last_key).rev();
+					self.read_range_aux(partition_hash, range, filter, limit)
+				}
+				None => {
+					let mut last_key = partition_hash.to_vec();
+					let lower = u128::from_be_bytes(last_key[16..32].try_into().unwrap());
+					last_key[16..32].copy_from_slice(&u128::to_be_bytes(lower + 1));
+					let range = self.store.range(..last_key).rev();
+					self.read_range_aux(partition_hash, range, filter, limit)
+				}
+			},
 		}
 	}