Add cursor pagination to report_combined view (#5244)

* add pagination cursor

* store timestamp instead of id in cursor (partial)

* Revert "store timestamp instead of id in cursor (partial)"

This reverts commit 89359dde4b.

* use paginated query builder

crates/db_schema/src/newtypes.rs

@@ -89,19 +89,19 @@ pub struct PersonMentionId(i32);
 #[cfg_attr(feature = "full", derive(DieselNewType, TS))]
 #[cfg_attr(feature = "full", ts(export))]
 /// The comment report id.
-pub struct CommentReportId(i32);
+pub struct CommentReportId(pub i32);
 
 #[derive(Debug, Copy, Clone, Hash, Eq, PartialEq, Serialize, Deserialize, Default)]
 #[cfg_attr(feature = "full", derive(DieselNewType, TS))]
 #[cfg_attr(feature = "full", ts(export))]
 /// The post report id.
-pub struct PostReportId(i32);
+pub struct PostReportId(pub i32);
 
 #[derive(Debug, Copy, Clone, Hash, Eq, PartialEq, Serialize, Deserialize, Default)]
 #[cfg_attr(feature = "full", derive(DieselNewType, TS))]
 #[cfg_attr(feature = "full", ts(export))]
 /// The private message report id.
-pub struct PrivateMessageReportId(i32);
+pub struct PrivateMessageReportId(pub i32);
 
 #[derive(Debug, Copy, Clone, Hash, Eq, PartialEq, Serialize, Deserialize, Default)]
 #[cfg_attr(feature = "full", derive(DieselNewType, TS))]

crates/db_schema/src/source/combined/report.rs

@@ -2,6 +2,8 @@ use crate::newtypes::{CommentReportId, PostReportId, PrivateMessageReportId, Rep
 #[cfg(feature = "full")]
 use crate::schema::report_combined;
 use chrono::{DateTime, Utc};
+#[cfg(feature = "full")]
+use i_love_jesus::CursorKeysModule;
 use serde::{Deserialize, Serialize};
 use serde_with::skip_serializing_none;
 #[cfg(feature = "full")]
@@ -9,10 +11,14 @@ use ts_rs::TS;
 
 #[skip_serializing_none]
 #[derive(PartialEq, Eq, Serialize, Deserialize, Debug, Clone)]
-#[cfg_attr(feature = "full", derive(Identifiable, Queryable, Selectable, TS))]
+#[cfg_attr(
+  feature = "full",
+  derive(Identifiable, Queryable, Selectable, TS, CursorKeysModule)
+)]
 #[cfg_attr(feature = "full", diesel(table_name = report_combined))]
 #[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 = report_combined_keys))]
 /// A combined reports table.
 pub struct ReportCombined {
   pub id: ReportCombinedId,

crates/db_views/src/report_combined_view.rs

@@ -3,6 +3,7 @@ use crate::structs::{
   LocalUserView,
   PostReportView,
   PrivateMessageReportView,
+  ReportCombinedPaginationCursor,
   ReportCombinedView,
   ReportCombinedViewInternal,
 };
@@ -13,8 +14,10 @@ use diesel::{
   JoinOnDsl,
   NullableExpressionMethods,
   QueryDsl,
+  SelectableHelper,
 };
 use diesel_async::RunQueryDsl;
+use i_love_jesus::PaginatedQueryBuilder;
 use lemmy_db_schema::{
   aliases::{self, creator_community_actions},
   newtypes::CommunityId,
@@ -36,8 +39,19 @@ use lemmy_db_schema::{
     private_message_report,
     report_combined,
   },
-  source::community::CommunityFollower,
+  source::{
-  utils::{actions, actions_alias, functions::coalesce, get_conn, limit_and_offset, DbPool},
+    combined::report::{report_combined_keys as key, ReportCombined},
+    community::CommunityFollower,
+  },
+  utils::{
+    actions,
+    actions_alias,
+    functions::coalesce,
+    get_conn,
+    limit_and_offset,
+    DbPool,
+    ReverseTimestampKey,
+  },
 };
 use lemmy_utils::error::LemmyResult;
 
@@ -94,12 +108,47 @@ impl ReportCombinedViewInternal {
   }
 }
 
+impl ReportCombinedPaginationCursor {
+  // get cursor for page that starts immediately after the given post
+  pub fn after_post(view: &ReportCombinedView) -> ReportCombinedPaginationCursor {
+    let (prefix, id) = match view {
+      ReportCombinedView::Comment(v) => ('C', v.comment_report.id.0),
+      ReportCombinedView::Post(v) => ('P', v.post_report.id.0),
+      ReportCombinedView::PrivateMessage(v) => ('M', v.private_message_report.id.0),
+    };
+    // hex encoding to prevent ossification
+    ReportCombinedPaginationCursor(format!("{prefix}{id:x}"))
+  }
+  pub async fn read(&self, pool: &mut DbPool<'_>) -> Result<PaginationCursorData, Error> {
+    let err_msg = || Error::QueryBuilderError("Could not parse pagination token".into());
+    let mut query = report_combined::table
+      .select(ReportCombined::as_select())
+      .into_boxed();
+    let (prefix, id_str) = self.0.split_at_checked(1).ok_or_else(err_msg)?;
+    let id = i32::from_str_radix(id_str, 16).map_err(|_err| err_msg())?;
+    query = match prefix {
+      "C" => query.filter(report_combined::comment_report_id.eq(id)),
+      "P" => query.filter(report_combined::post_report_id.eq(id)),
+      "M" => query.filter(report_combined::private_message_report_id.eq(id)),
+      _ => return Err(err_msg()),
+    };
+    let token = query.first(&mut get_conn(pool).await?).await?;
+
+    Ok(PaginationCursorData(token))
+  }
+}
+
+#[derive(Clone)]
+pub struct PaginationCursorData(ReportCombined);
+
 #[derive(Default)]
 pub struct ReportCombinedQuery {
   pub community_id: Option<CommunityId>,
   pub page: Option<i64>,
   pub limit: Option<i64>,
   pub unresolved_only: bool,
+  pub page_after: Option<PaginationCursorData>,
+  pub page_back: bool,
 }
 
 impl ReportCombinedQuery {
@@ -237,18 +286,6 @@ impl ReportCombinedQuery {
       query = query.filter(community::id.eq(community_id));
     }
 
-    // If viewing all reports, order by newest, but if viewing unresolved only, show the oldest
-    // first (FIFO)
-    if options.unresolved_only {
-      query = query
-        .filter(post_report::resolved.eq(false))
-        .or_filter(comment_report::resolved.eq(false))
-        .or_filter(private_message_report::resolved.eq(false))
-        .order_by(report_combined::published.asc());
-    } else {
-      query = query.order_by(report_combined::published.desc());
-    }
-
     // If its not an admin, get only the ones you mod
     if !user.local_user.admin {
       query = query.filter(community_actions::became_moderator.is_not_null());
@@ -258,6 +295,36 @@ impl ReportCombinedQuery {
 
     query = query.limit(limit).offset(offset);
 
+    let mut query = PaginatedQueryBuilder::new(query);
+
+    let page_after = options.page_after.map(|c| c.0);
+
+    if options.page_back {
+      query = query.before(page_after).limit_and_offset_from_end();
+    } else {
+      query = query.after(page_after);
+    }
+
+    // If viewing all reports, order by newest, but if viewing unresolved only, show the oldest
+    // first (FIFO)
+    if options.unresolved_only {
+      query = query
+        .filter(
+          post_report::resolved
+            .eq(false)
+            .or(comment_report::resolved.eq(false))
+            .or(private_message_report::resolved.eq(false)),
+        )
+        // TODO: when a `then_asc` method is added, use it here, make the id sort direction match,
+        // and remove the separate index; unless additional columns are added to this sort
+        .then_desc(ReverseTimestampKey(key::published));
+    } else {
+      query = query.then_desc(key::published);
+    }
+
+    // Tie breaker
+    query = query.then_desc(key::id);
+
     let res = query.load::<ReportCombinedViewInternal>(conn).await?;
 
     // Map the query results to the enum

crates/db_views/src/structs.rs

@@ -126,6 +126,12 @@ pub struct PostReportView {
 #[cfg_attr(feature = "full", ts(export))]
 pub struct PaginationCursor(pub String);
 
+/// like PaginationCursor but for the report_combined table
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "full", derive(ts_rs::TS))]
+#[cfg_attr(feature = "full", ts(export))]
+pub struct ReportCombinedPaginationCursor(pub String);
+
 #[skip_serializing_none]
 #[derive(Debug, PartialEq, Serialize, Deserialize, Clone)]
 #[cfg_attr(feature = "full", derive(TS, Queryable))]

migrations/2024-11-26-115042_add_combined_tables/up.sql

@@ -17,7 +17,9 @@ CREATE TABLE report_combined (
     UNIQUE (post_report_id, comment_report_id, private_message_report_id)
 );
 
-CREATE INDEX idx_report_combined_published ON report_combined (published DESC);
+CREATE INDEX idx_report_combined_published ON report_combined (published DESC, id DESC);
+
+CREATE INDEX idx_report_combined_published_asc ON report_combined (reverse_timestamp_sort (published) DESC, id DESC);
 
 -- Updating the history
 INSERT INTO report_combined (published, post_report_id)