Simplify post listing queries.

Use named sqlc arguments, scope vote aggregation to selected roots, join viewer votes directly, and add the indexes and drift migration required by the resulting access paths.

db/queries/posts.sql

@@ -2,7 +2,18 @@
 INSERT INTO posts (
   id, parent_id, author_id, title, body, city, post_date, hidden, created_at, updated_at
 )
-VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10);
+VALUES (
+  sqlc.arg(id),
+  sqlc.arg(parent_id),
+  sqlc.arg(author_id),
+  sqlc.arg(title),
+  sqlc.arg(body),
+  sqlc.arg(city),
+  sqlc.arg(post_date),
+  sqlc.arg(hidden),
+  sqlc.arg(created_at),
+  sqlc.arg(updated_at)
+);
 
 -- name: GetPost :one
 SELECT
@@ -10,13 +21,13 @@ SELECT
   p.title, p.body, p.city, p.post_date, p.hidden, p.created_at, p.updated_at
 FROM posts p
 JOIN users u ON u.id = p.author_id
-WHERE p.id = $1;
+WHERE p.id = sqlc.arg(id);
 
 -- name: ListPostThread :many
 WITH RECURSIVE thread AS (
   SELECT p.*
   FROM posts p
-  WHERE p.id = $1 AND p.parent_id IS NULL
+  WHERE p.id = sqlc.arg(root_id) AND p.parent_id IS NULL
 
   UNION ALL
 
@@ -35,8 +46,10 @@ ORDER BY thread.created_at, thread.id;
 
 -- name: UpdatePost :execrows
 UPDATE posts
-SET body = $2, updated_at = $3
-WHERE id = $1;
+SET
+  body = sqlc.arg(body),
+  updated_at = sqlc.arg(updated_at)
+WHERE id = sqlc.arg(id);
 
 -- name: ListRootPosts :many
 WITH RECURSIVE roots AS (
@@ -47,8 +60,9 @@ WITH RECURSIVE roots AS (
     AND p.hidden = 0
 ),
 thread AS (
-  SELECT roots.id AS root_id, roots.id AS post_id, roots.author_id
+  SELECT roots.id AS root_id, child.id AS post_id, child.author_id
   FROM roots
+  JOIN posts child ON child.parent_id = roots.id
 
   UNION ALL
 
@@ -57,15 +71,16 @@ thread AS (
   JOIN posts child ON child.parent_id = thread.post_id
 ),
 answered AS (
-  SELECT thread.root_id, bool_or(u.role = 'admin' AND thread.post_id <> thread.root_id) AS answered
+  SELECT DISTINCT thread.root_id
   FROM thread
   JOIN users u ON u.id = thread.author_id
-  GROUP BY thread.root_id
+  WHERE u.role = 'admin'
 ),
 scores AS (
-  SELECT post_id, COALESCE(SUM(value), 0)::bigint AS score
-  FROM post_votes
-  GROUP BY post_id
+  SELECT votes.post_id, SUM(votes.value)::bigint AS score
+  FROM roots
+  JOIN post_votes votes ON votes.post_id = roots.id
+  GROUP BY votes.post_id
 )
 SELECT
   roots.id, roots.parent_id, roots.author_id,
@@ -73,17 +88,15 @@ SELECT
   roots.title, roots.body, roots.city, roots.post_date,
   roots.hidden, roots.created_at, roots.updated_at,
   COALESCE(scores.score, 0)::bigint AS score,
-  COALESCE(answered.answered, false)::bool AS answered,
-  COALESCE((
-    SELECT post_votes.value
-    FROM post_votes
-    WHERE post_votes.user_id = sqlc.arg(viewer_id)
-      AND post_votes.post_id = roots.id
-  ), 0)::bigint AS user_vote
+  (answered.root_id IS NOT NULL)::bool AS answered,
+  COALESCE(viewer_vote.value, 0)::bigint AS user_vote
 FROM roots
 JOIN users u ON u.id = roots.author_id
 LEFT JOIN scores ON scores.post_id = roots.id
 LEFT JOIN answered ON answered.root_id = roots.id
+LEFT JOIN post_votes viewer_vote
+  ON viewer_vote.user_id = sqlc.arg(viewer_id)
+  AND viewer_vote.post_id = roots.id
 ORDER BY score DESC, roots.created_at, roots.id
 LIMIT sqlc.arg(row_limit);
 
@@ -91,22 +104,20 @@ LIMIT sqlc.arg(row_limit);
 SELECT EXISTS(
   SELECT 1
   FROM posts
-  WHERE id = $1 AND parent_id IS NULL AND hidden = 0
+  WHERE id = sqlc.arg(id) AND parent_id IS NULL AND hidden = 0
 )::bool;
 
 -- name: DeletePostVote :exec
 DELETE FROM post_votes
-WHERE user_id = $1 AND post_id = $2;
+WHERE user_id = sqlc.arg(user_id)
+  AND post_id = sqlc.arg(post_id);
 
 -- name: UpsertPostVoteOnVisibleRoot :execrows
 INSERT INTO post_votes (user_id, post_id, value)
-SELECT $1, $2, $3
+SELECT sqlc.arg(user_id), sqlc.arg(post_id), sqlc.arg(value)
 FROM posts p
-WHERE p.id = $2 AND p.parent_id IS NULL AND p.hidden = 0
+WHERE p.id = sqlc.arg(post_id)
+  AND p.parent_id IS NULL
+  AND p.hidden = 0
 ON CONFLICT (user_id, post_id) DO UPDATE
-SET value = excluded.value
-WHERE EXISTS (
-  SELECT 1
-  FROM posts p2
-  WHERE p2.id = excluded.post_id AND p2.parent_id IS NULL AND p2.hidden = 0
-);
+SET value = excluded.value;