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Correctly combine sorts in post view cursor-based pagination (#4247)

Browse source 
* Update post_view.rs

* Update post_view.rs

* Update Cargo.toml

* Update post_view.rs

* fix

* Update post_view.rs

---------

Co-authored-by: SleeplessOne1917 <abias1122@gmail.com>
Co-authored-by: Dessalines <dessalines@users.noreply.github.com>
This commit is contained in:
dullbananas 2023-12-14 05:10:01 -07:00 committed by GitHub
parent 01aa17f38e
commit 32afc32bc0
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3 changed files with 204 additions and 138 deletions
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1
Cargo.lock generated
View file

@ -2685,6 +2685,7 @@ name = "lemmy_db_views"
version = "0.19.0-rc.15"
dependencies = [
"actix-web",
"chrono",
"diesel",
"diesel-async",
"diesel_ltree",

1
crates/db_views/Cargo.toml
View file

@ -41,3 +41,4 @@ actix-web = { workspace = true, optional = true }
[dev-dependencies]
serial_test = { workspace = true }
tokio = { workspace = true }
chrono = { workspace = true }

330
crates/db_views/src/post_view.rs
View file

@ -1,15 +1,13 @@
use crate::structs::{LocalUserView, PaginationCursor, PostView};
use diesel::{
debug_query,
dsl::{self, exists, not, IntervalDsl},
expression::AsExpression,
dsl::{exists, not, IntervalDsl},
pg::Pg,
result::Error,
sql_function,
sql_types::{self, SingleValue, SqlType, Timestamptz},
sql_types,
BoolExpressionMethods,
BoxableExpression,
Expression,
ExpressionMethods,
IntoSql,
JoinOnDsl,
@ -35,12 +33,12 @@ use lemmy_db_schema::{
person_block,
person_post_aggregates,
post,
post_aggregates::{self, newest_comment_time},
post_aggregates,
post_like,
post_read,
post_saved,
},
utils::{fuzzy_search, get_conn, limit_and_offset, DbConn, DbPool, ListFn, Queries, ReadFn},
utils::{fuzzy_search, get_conn, limit_and_offset, now, DbConn, DbPool, ListFn, Queries, ReadFn},
ListingType,
SortType,
};
@ -48,53 +46,32 @@ use tracing::debug;
sql_function!(fn coalesce(x: sql_types::Nullable<sql_types::BigInt>, y: sql_types::BigInt) -> sql_types::BigInt);
fn order_and_page_filter_desc<Q, C, T>(
query: Q,
column: C,
options: &PostQuery,
getter: impl Fn(&PostAggregates) -> T,
) -> Q
where
Q: diesel::query_dsl::methods::ThenOrderDsl<dsl::Desc<C>, Output = Q>
+ diesel::query_dsl::methods::ThenOrderDsl<dsl::Asc<C>, Output = Q>
+ diesel::query_dsl::methods::FilterDsl<dsl::GtEq<C, T>, Output = Q>
+ diesel::query_dsl::methods::FilterDsl<dsl::LtEq<C, T>, Output = Q>,
C: Expression + Copy,
C::SqlType: SingleValue + SqlType,
T: AsExpression<C::SqlType>,
{
let mut query = query.then_order_by(column.desc());
if let Some(before) = &options.page_before_or_equal {
query = query.filter(column.ge(getter(&before.0)));
}
if let Some(after) = &options.page_after {
query = query.filter(column.le(getter(&after.0)));
}
query
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
enum Ord {
Desc,
Asc,
}
fn order_and_page_filter_asc<Q, C, T>(
query: Q,
column: C,
options: &PostQuery,
getter: impl Fn(&PostAggregates) -> T,
) -> Q
where
Q: diesel::query_dsl::methods::ThenOrderDsl<dsl::Asc<C>, Output = Q>
+ diesel::query_dsl::methods::FilterDsl<dsl::LtEq<C, T>, Output = Q>
+ diesel::query_dsl::methods::FilterDsl<dsl::GtEq<C, T>, Output = Q>,
C: Expression + Copy,
C::SqlType: SingleValue + SqlType,
T: AsExpression<C::SqlType>,
{
let mut query = query.then_order_by(column.asc());
if let Some(before) = &options.page_before_or_equal {
query = query.filter(column.le(getter(&before.0)));
struct PaginationCursorField<Q, QS> {
then_order_by_desc: fn(Q) -> Q,
then_order_by_asc: fn(Q) -> Q,
le: fn(&PostAggregates) -> Box<dyn BoxableExpression<QS, Pg, SqlType = sql_types::Bool>>,
ge: fn(&PostAggregates) -> Box<dyn BoxableExpression<QS, Pg, SqlType = sql_types::Bool>>,
ne: fn(&PostAggregates) -> Box<dyn BoxableExpression<QS, Pg, SqlType = sql_types::Bool>>,
}
if let Some(after) = &options.page_after {
query = query.filter(column.ge(getter(&after.0)));
/// Returns `PaginationCursorField<_, _>` for the given name
macro_rules! field {
($name:ident) => {
// Type inference doesn't work if normal method call syntax is used
PaginationCursorField {
then_order_by_desc: |query| QueryDsl::then_order_by(query, post_aggregates::$name.desc()),
then_order_by_asc: |query| QueryDsl::then_order_by(query, post_aggregates::$name.asc()),
le: |e| Box::new(post_aggregates::$name.le(e.$name)),
ge: |e| Box::new(post_aggregates::$name.ge(e.$name)),
ne: |e| Box::new(post_aggregates::$name.ne(e.$name)),
}
query
};
}
fn queries<'a>() -> Queries<
@ -334,16 +311,6 @@ fn queries<'a>() -> Queries<
.filter(community::removed.eq(false))
.filter(post::removed.eq(false));
}
if options.community_id.is_none() || options.community_id_just_for_prefetch {
query = order_and_page_filter_desc(query, post_aggregates::featured_local, &options, |e| {
e.featured_local
});
} else {
query =
order_and_page_filter_desc(query, post_aggregates::featured_community, &options, |e| {
e.featured_community
});
}
if let Some(community_id) = options.community_id {
query = query.filter(post_aggregates::community_id.eq(community_id));
}
@ -481,86 +448,102 @@ fn queries<'a>() -> Queries<
)));
query = query.filter(not(is_creator_blocked(person_id)));
}
let now = diesel::dsl::now.into_sql::<Timestamptz>();
let featured_field = if options.community_id.is_none() || options.community_id_just_for_prefetch
{
use post_aggregates::{
comments,
controversy_rank,
hot_rank,
hot_rank_active,
published,
scaled_rank,
score,
field!(featured_local)
} else {
field!(featured_community)
};
match options.sort.as_ref().unwrap_or(&SortType::Hot) {
SortType::Active => {
query =
order_and_page_filter_desc(query, hot_rank_active, &options, |e| e.hot_rank_active);
query = order_and_page_filter_desc(query, published, &options, |e| e.published);
}
SortType::Hot => {
query = order_and_page_filter_desc(query, hot_rank, &options, |e| e.hot_rank);
query = order_and_page_filter_desc(query, published, &options, |e| e.published);
}
SortType::Scaled => {
query = order_and_page_filter_desc(query, scaled_rank, &options, |e| e.scaled_rank);
query = order_and_page_filter_desc(query, published, &options, |e| e.published);
}
SortType::Controversial => {
query =
order_and_page_filter_desc(query, controversy_rank, &options, |e| e.controversy_rank);
query = order_and_page_filter_desc(query, published, &options, |e| e.published);
}
SortType::New => {
query = order_and_page_filter_desc(query, published, &options, |e| e.published)
}
SortType::Old => {
query = order_and_page_filter_asc(query, published, &options, |e| e.published)
}
SortType::NewComments => {
query = order_and_page_filter_desc(query, newest_comment_time, &options, |e| {
e.newest_comment_time
})
}
SortType::MostComments => {
query = order_and_page_filter_desc(query, comments, &options, |e| e.comments);
query = order_and_page_filter_desc(query, published, &options, |e| e.published);
}
SortType::TopAll => {
query = order_and_page_filter_desc(query, score, &options, |e| e.score);
query = order_and_page_filter_desc(query, published, &options, |e| e.published);
}
o @ (SortType::TopYear
| SortType::TopMonth
| SortType::TopWeek
| SortType::TopDay
| SortType::TopHour
| SortType::TopSixHour
| SortType::TopTwelveHour
| SortType::TopThreeMonths
| SortType::TopSixMonths
| SortType::TopNineMonths) => {
let interval = match o {
SortType::TopYear => 1.years(),
SortType::TopMonth => 1.months(),
SortType::TopWeek => 1.weeks(),
SortType::TopDay => 1.days(),
SortType::TopHour => 1.hours(),
SortType::TopSixHour => 6.hours(),
SortType::TopTwelveHour => 12.hours(),
SortType::TopThreeMonths => 3.months(),
SortType::TopSixMonths => 6.months(),
SortType::TopNineMonths => 9.months(),
_ => return Err(Error::NotFound),
let (main_sort, top_sort_interval) = match options.sort.unwrap_or(SortType::Hot) {
SortType::Active => ((Ord::Desc, field!(hot_rank_active)), None),
SortType::Hot => ((Ord::Desc, field!(hot_rank)), None),
SortType::Scaled => ((Ord::Desc, field!(scaled_rank)), None),
SortType::Controversial => ((Ord::Desc, field!(controversy_rank)), None),
SortType::New => ((Ord::Desc, field!(published)), None),
SortType::Old => ((Ord::Asc, field!(published)), None),
SortType::NewComments => ((Ord::Desc, field!(newest_comment_time)), None),
SortType::MostComments => ((Ord::Desc, field!(comments)), None),
SortType::TopAll => ((Ord::Desc, field!(score)), None),
SortType::TopYear => ((Ord::Desc, field!(score)), Some(1.years())),
SortType::TopMonth => ((Ord::Desc, field!(score)), Some(1.months())),
SortType::TopWeek => ((Ord::Desc, field!(score)), Some(1.weeks())),
SortType::TopDay => ((Ord::Desc, field!(score)), Some(1.days())),
SortType::TopHour => ((Ord::Desc, field!(score)), Some(1.hours())),
SortType::TopSixHour => ((Ord::Desc, field!(score)), Some(6.hours())),
SortType::TopTwelveHour => ((Ord::Desc, field!(score)), Some(12.hours())),
SortType::TopThreeMonths => ((Ord::Desc, field!(score)), Some(3.months())),
SortType::TopSixMonths => ((Ord::Desc, field!(score)), Some(6.months())),
SortType::TopNineMonths => ((Ord::Desc, field!(score)), Some(9.months())),
};
query = query.filter(post_aggregates::published.gt(now - interval));
query = order_and_page_filter_desc(query, score, &options, |e| e.score);
query = order_and_page_filter_desc(query, published, &options, |e| e.published);
}
if let Some(interval) = top_sort_interval {
query = query.filter(post_aggregates::published.gt(now() - interval));
}
let tie_breaker = match options.sort.unwrap_or(SortType::Hot) {
// A second time-based sort would not be very useful
SortType::New | SortType::Old | SortType::NewComments => None,
_ => Some((Ord::Desc, field!(published))),
};
let sorts = [
Some((Ord::Desc, featured_field)),
Some(main_sort),
tie_breaker,
];
let sorts_iter = sorts.iter().flatten();
// This loop does almost the same thing as sorting by and comparing tuples. If the rows were
// only sorted by 1 field called `foo` in descending order, then it would be like this:
//
// ```
// query = query.then_order_by(foo.desc());
// if let Some(first) = &options.page_after {
// query = query.filter(foo.le(first.foo));
// }
// if let Some(last) = &page_before_or_equal {
// query = query.filter(foo.ge(last.foo));
// }
// ```
//
// If multiple rows have the same value for a sorted field, then they are
// grouped together, and the rows in that group are sorted by the next fields.
// When checking if a row is within the range determined by the cursors, a field
// that's sorted after other fields is only compared if the row and the cursor
// are in the same group created by the previous sort, which is checked by using
// `or` to skip the comparison if any previously sorted field is not equal.
for (i, (order, field)) in sorts_iter.clone().enumerate() {
// Both cursors are treated as inclusive here. `page_after` is made exclusive
// by adding `1` to the offset.
let (then_order_by_field, compare_first, compare_last) = match order {
Ord::Desc => (field.then_order_by_desc, field.le, field.ge),
Ord::Asc => (field.then_order_by_asc, field.ge, field.le),
};
query = then_order_by_field(query);
for (cursor_data, compare) in [
(&options.page_after, compare_first),
(&options.page_before_or_equal, compare_last),
] {
let Some(cursor_data) = cursor_data else {
continue;
};
let mut condition: Box<dyn BoxableExpression<_, Pg, SqlType = sql_types::Bool>> =
Box::new(compare(&cursor_data.0));
// For each field that was sorted before the current one, skip the filter by changing
// `condition` to `true` if the row's value doesn't equal the cursor's value.
for (_, other_field) in sorts_iter.clone().take(i) {
condition = Box::new(condition.or((other_field.ne)(&cursor_data.0)));
}
query = query.filter(condition);
}
}
let (limit, mut offset) = limit_and_offset(options.page, options.limit)?;
if options.page_after.is_some() {
// always skip exactly one post because that's the last post of the previous page
@ -737,15 +720,17 @@ mod tests {
#![allow(clippy::indexing_slicing)]
use crate::{
post_view::{PostQuery, PostView},
post_view::{PaginationCursorData, PostQuery, PostView},
structs::LocalUserView,
};
use chrono::Utc;
use lemmy_db_schema::{
aggregates::structs::PostAggregates,
impls::actor_language::UNDETERMINED_ID,
newtypes::LanguageId,
source::{
actor_language::LocalUserLanguage,
comment::{Comment, CommentInsertForm},
community::{Community, CommunityInsertForm, CommunityModerator, CommunityModeratorForm},
community_block::{CommunityBlock, CommunityBlockForm},
instance::Instance,
@ -762,6 +747,7 @@ mod tests {
SubscribedType,
};
use serial_test::serial;
use std::time::Duration;
struct Data {
inserted_instance: Instance,
@ -1431,6 +1417,84 @@ mod tests {
cleanup(data, pool).await;
}
#[tokio::test]
#[serial]
async fn pagination_includes_each_post_once() {
let pool = &build_db_pool_for_tests().await;
let pool = &mut pool.into();
let data = init_data(pool).await;
let community_form = CommunityInsertForm::builder()
.name("yes".to_string())
.title("yes".to_owned())
.public_key("pubkey".to_string())
.instance_id(data.inserted_instance.id)
.build();
let inserted_community = Community::create(pool, &community_form).await.unwrap();
let mut inserted_post_ids = vec![];
let mut inserted_comment_ids = vec![];
// Create 150 posts with varying non-correlating values for publish date, number of comments, and featured
for comments in 0..10 {
for _ in 0..15 {
let post_form = PostInsertForm::builder()
.name("keep Christ in Christmas".to_owned())
.creator_id(data.local_user_view.person.id)
.community_id(inserted_community.id)
.featured_local(Some((comments % 2) == 0))
.featured_community(Some((comments % 2) == 0))
.published(Some(Utc::now() - Duration::from_secs(comments % 3)))
.build();
let inserted_post = Post::create(pool, &post_form).await.unwrap();
inserted_post_ids.push(inserted_post.id);
for _ in 0..comments {
let comment_form = CommentInsertForm::builder()
.creator_id(data.local_user_view.person.id)
.post_id(inserted_post.id)
.content("yes".to_owned())
.build();
let inserted_comment = Comment::create(pool, &comment_form, None).await.unwrap();
inserted_comment_ids.push(inserted_comment.id);
}
}
}
let mut listed_post_ids = vec![];
let mut page_after = None;
loop {
let post_listings = PostQuery {
community_id: Some(inserted_community.id),
sort: Some(SortType::MostComments),
limit: Some(10),
page_after,
..Default::default()
}
.list(pool)
.await
.unwrap();
listed_post_ids.extend(post_listings.iter().map(|p| p.post.id));
if let Some(p) = post_listings.into_iter().last() {
page_after = Some(PaginationCursorData(p.counts));
} else {
break;
}
}
inserted_post_ids.sort_unstable_by_key(|id| id.0);
listed_post_ids.sort_unstable_by_key(|id| id.0);
assert_eq!(inserted_post_ids, listed_post_ids);
Community::delete(pool, inserted_community.id)
.await
.unwrap();
cleanup(data, pool).await;
}
async fn cleanup(data: Data, pool: &mut DbPool<'_>) {
let num_deleted = Post::delete(pool, data.inserted_post.id).await.unwrap();
Community::delete(pool, data.inserted_community.id)