fix(blog::api) fix pagination for GET posts

backend/server/src/modules/blog/api/posts/count_tag_filtered_posts.sql

@@ -0,0 +1,20 @@
+WITH filtered_posts AS
+         (SELECT p.id, p.date_created
+          FROM posts p
+          WHERE $1::text[] IS NULL
+             OR (
+              CASE
+                  WHEN $4 THEN (SELECT COUNT(DISTINCT t.name)
+                                FROM post_tag pt
+                                         JOIN tags t ON pt.tag = t.id
+                                WHERE pt.post = p.id
+                                  AND t.name = ANY ($1::text[])) = cardinality($1)
+                  ELSE EXISTS (SELECT 1
+                               FROM post_tag pt
+                                        JOIN tags t ON pt.tag = t.id
+                               WHERE pt.post = p.id
+                                 AND t.name = ANY ($1::text[]))
+                  END
+              ))
+SELECT COUNT(*) AS total_count
+FROM filtered_posts;

backend/server/src/modules/blog/api/posts/get.rs

@@ -106,20 +106,25 @@ struct UuidRow {
     id: Uuid,
 }
 
-const GET_POST_WITH_BRIEF_MODEL: &str = include_str!("get_post_with_brief_model.sql");
+const I32_PLACEHOLDER: i32 = 0;
+
+const COUNT_TAG_FILTERED_POSTS: &str = include_str!("count_tag_filtered_posts.sql");
 const SELECT_POST_WITH_TAG_FILTER_PAGINATED: &str =
     include_str!("select_post_with_tag_filter_paginated.sql");
+const GET_POST_WITH_BRIEF_MODEL: &str = include_str!("get_post_with_brief_model.sql");
 
 pub async fn handler(
     State(db): State<PgPool>,
     Query(search_params): Query<SearchParams>,
 ) -> impl IntoResponse {
-    dbg!(&search_params.tags);
-    dbg!(&search_params.match_all);
-
     let page = search_params.page.unwrap_or(1);
     let page_size = search_params.page_size.unwrap_or(PAGE_SIZE);
-    let page_count = match sqlx::query_scalar::<_, i64>("SELECT COUNT(*) FROM posts")
+
+    let page_count = match sqlx::query_scalar::<_, i64>(COUNT_TAG_FILTERED_POSTS)
+        .bind(&search_params.tags)
+        .bind(I32_PLACEHOLDER) // not used, but help sqlx/psql hit cache
+        .bind(I32_PLACEHOLDER)
+        .bind(search_params.match_all)
         .fetch_one(&db)
         .await
     {

backend/server/src/modules/blog/api/posts/select_post_with_tag_filter_paginated.sql

@@ -1,21 +1,22 @@
-SELECT p.id
+WITH filtered_posts AS
-FROM posts p
+         (SELECT p.id, p.date_created
-WHERE $1::text[] IS NULL
+          FROM posts p
-   OR (
+          WHERE $1::text[] IS NULL
-    CASE
+             OR (
-        WHEN $4 THEN (SELECT COUNT(DISTINCT t.name)
+              CASE
-                      FROM post_tag pt
+                  WHEN $4 THEN (SELECT COUNT(DISTINCT t.name)
-                               JOIN tags t ON pt.tag = t.id
+                                FROM post_tag pt
-                      WHERE pt.post = p.id
+                                         JOIN tags t ON pt.tag = t.id
-                        AND t.name = ANY ($1::text[]))
+                                WHERE pt.post = p.id
-            = cardinality($1)
+                                  AND t.name = ANY ($1::text[])) = cardinality($1)
-        ELSE
+                  ELSE EXISTS (SELECT 1
-            EXISTS (SELECT 1
+                               FROM post_tag pt
-                    FROM post_tag pt
+                                        JOIN tags t ON pt.tag = t.id
-                             JOIN tags t ON pt.tag = t.id
+                               WHERE pt.post = p.id
-                    WHERE pt.post = p.id
+                                 AND t.name = ANY ($1::text[]))
-                      AND t.name = ANY ($1::text[]))
+                  END
-        END
+              ))
-    )
+SELECT id
-ORDER BY p.date_created DESC
+FROM filtered_posts
+ORDER BY date_created DESC
 LIMIT $2 OFFSET $3;