Allow descending order of chain query filter

crates/holochain_state/src/source_chain.rs

@@ -764,14 +764,15 @@ where
                     });
                     sql.push_str(
                         "
-                )
-                AND
-                (:entry_type IS NULL OR Action.entry_type = :entry_type)
-                AND
-                (:action_type IS NULL OR Action.type = :action_type)
-                ORDER BY Action.seq ASC
-                ",
+                        )
+                        AND
+                        (:entry_type IS NULL OR Action.entry_type = :entry_type)
+                        AND
+                        (:action_type IS NULL OR Action.type = :action_type)
+                        ORDER BY Action.seq 
+                        ",
                     );
+                    sql.push_str(if query.order_descending {" DESC"} else {" ASC"});
                     let mut stmt = txn.prepare(&sql)?;
                     let records = stmt
                         .query_and_then(
@@ -2000,6 +2001,7 @@ pub mod tests {
                     entry_type: entry_type.clone(),
                     entry_hashes: entry_hashes.clone(),
                     include_entries,
+                    order_descending: false,
                 };
                 if sequence_range != ChainQueryFilterRange::Unbounded
                     && (action_type.is_some()

crates/holochain_zome_types/CHANGELOG.md

@@ -4,6 +4,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased](https://github.com/holochain/holochain/holochain_zome_types-v0.0.2-alpha.1...HEAD)
 
+`ChainQueryFilter` has a `descending()` function which will cause the query results to be returned in descending order. This can be reversed by calling `ascending()`. The default order is still ascending. [\#1539](https://github.com/holochain/holochain/pull/1539)
+
 ## 0.0.44
 
 ## 0.0.43

crates/holochain_zome_types/src/query.rs

@@ -78,6 +78,8 @@ pub struct ChainQueryFilter {
     pub action_type: Option<ActionType>,
     /// Include the entries in the records
     pub include_entries: bool,
+    /// The query should be ordered in descending order (default is ascending)
+    pub order_descending: bool,
 }
 
 #[derive(Clone, Debug, PartialEq, serde::Serialize, serde::Deserialize, SerializedBytes)]
@@ -207,6 +209,18 @@ impl ChainQueryFilter {
         self
     }
 
+    /// Set the order to ascending.
+    pub fn ascending(mut self) -> Self {
+        self.order_descending = false;
+        self
+    }
+
+    /// Set the order to ascending.
+    pub fn descending(mut self) -> Self {
+        self.order_descending = true;
+        self
+    }
+
     /// If the sequence range supports fork disambiguation, apply it to remove
     /// actions that are not in the correct branch.
     /// Numerical range bounds do NOT support fork disambiguation, and neither
@@ -401,6 +415,13 @@ mod tests {
             map_query(&query_2, &actions),
             [false, true, false, true, false, false, false].to_vec()
         );
+        assert_eq!(
+            map_query(&query_2.descending(), &actions),
+            [false, true, false, true, false, false, false]
+                .into_iter()
+                .rev()
+                .collect::<Vec<_>>()
+        );
     }
 
     #[test]