Post view: move cursor pagination to separate library, add backward pagination to PostQuery

Cargo.toml

@@ -157,6 +157,7 @@ tokio-postgres = "0.7.10"
 tokio-postgres-rustls = "0.10.0"
 enum-map = "2.7"
 moka = { version = "0.12.1", features = ["future"] }
+i-love-jesus = { version = "0.1.0" }
 clap = { version = "4.4.11", features = ["derive"] }
 pretty_assertions = "1.4.0"
 

crates/db_schema/Cargo.toml

@@ -36,6 +36,7 @@ full = [
   "tokio-postgres",
   "tokio-postgres-rustls",
   "rustls",
+  "i-love-jesus",
 ]
 
 [dependencies]
@@ -76,6 +77,7 @@ tokio-postgres = { workspace = true, optional = true }
 tokio-postgres-rustls = { workspace = true, optional = true }
 rustls = { workspace = true, optional = true }
 uuid = { workspace = true, features = ["v4"] }
+i-love-jesus = { workspace = true, optional = true }
 anyhow = { workspace = true }
 
 [dev-dependencies]

crates/db_schema/src/aggregates/structs.rs

@@ -9,6 +9,8 @@ use crate::schema::{
   site_aggregates,
 };
 use chrono::{DateTime, Utc};
+#[cfg(feature = "full")]
+use i_love_jesus::CursorKeysModule;
 use serde::{Deserialize, Serialize};
 #[cfg(feature = "full")]
 use ts_rs::TS;
@@ -93,13 +95,21 @@ pub struct PersonAggregates {
 #[derive(PartialEq, Debug, Serialize, Deserialize, Clone)]
 #[cfg_attr(
   feature = "full",
-  derive(Queryable, Selectable, Associations, Identifiable, TS)
+  derive(
+    Queryable,
+    Selectable,
+    Associations,
+    Identifiable,
+    TS,
+    CursorKeysModule
+  )
 )]
 #[cfg_attr(feature = "full", diesel(table_name = post_aggregates))]
 #[cfg_attr(feature = "full", diesel(belongs_to(crate::source::post::Post)))]
 #[cfg_attr(feature = "full", diesel(primary_key(post_id)))]
 #[cfg_attr(feature = "full", diesel(check_for_backend(diesel::pg::Pg)))]
 #[cfg_attr(feature = "full", ts(export))]
+#[cfg_attr(feature = "full", cursor_keys_module(name = post_aggregates_keys))]
 /// Aggregate data for a post.
 pub struct PostAggregates {
   pub post_id: PostId,

crates/db_schema/src/utils.rs

@@ -18,7 +18,7 @@ use diesel::{
   query_dsl::methods::LimitDsl,
   result::{ConnectionError, ConnectionResult, Error as DieselError, Error::QueryBuilderError},
   serialize::{Output, ToSql},
-  sql_types::{Text, Timestamptz},
+  sql_types::{self, Text, Timestamptz},
   IntoSql,
   PgConnection,
 };
@@ -32,6 +32,7 @@ use diesel_async::{
 };
 use diesel_migrations::EmbeddedMigrations;
 use futures_util::{future::BoxFuture, Future, FutureExt};
+use i_love_jesus::CursorKey;
 use lemmy_utils::{
   error::{LemmyError, LemmyErrorExt, LemmyErrorType},
   settings::SETTINGS,
@@ -153,6 +154,25 @@ macro_rules! try_join_with_pool {
   }};
 }
 
+pub struct ReverseTimestampKey<K>(pub K);
+
+impl<K, C> CursorKey<C> for ReverseTimestampKey<K>
+where
+  K: CursorKey<C, SqlType = Timestamptz>,
+{
+  type SqlType = sql_types::BigInt;
+  type CursorValue = functions::reverse_timestamp_sort::HelperType<K::CursorValue>;
+  type SqlValue = functions::reverse_timestamp_sort::HelperType<K::SqlValue>;
+
+  fn get_cursor_value(cursor: &C) -> Self::CursorValue {
+    functions::reverse_timestamp_sort(K::get_cursor_value(cursor))
+  }
+
+  fn get_sql_value() -> Self::SqlValue {
+    functions::reverse_timestamp_sort(K::get_sql_value())
+  }
+}
+
 /// Includes an SQL comment before `T`, which can be used to label auto_explain output
 #[derive(QueryId)]
 pub struct Commented<T> {
@@ -424,6 +444,8 @@ pub mod functions {
     fn controversy_rank(upvotes: BigInt, downvotes: BigInt, score: BigInt) -> Double;
   }
 
+  sql_function!(fn reverse_timestamp_sort(time: Timestamptz) -> BigInt);
+
   sql_function!(fn lower(x: Text) -> Text);
 
   // really this function is variadic, this just adds the two-argument version

crates/db_views/Cargo.toml

@@ -23,6 +23,7 @@ full = [
   "tracing",
   "ts-rs",
   "actix-web",
+  "i-love-jesus",
   "lemmy_db_schema/full",
 ]
 
@@ -37,6 +38,7 @@ serde_with = { workspace = true }
 tracing = { workspace = true, optional = true }
 ts-rs = { workspace = true, optional = true }
 actix-web = { workspace = true, optional = true }
+i-love-jesus = { workspace = true, optional = true }
 
 [dev-dependencies]
 serial_test = { workspace = true }