feat(search): use postgres native fulltext search

lib/bdfr_browser/comment.ex

@@ -46,8 +46,6 @@ defmodule BdfrBrowser.Comment do
   def search(str), do: search(str, nil)
 
   def search(str, subreddits) when is_nil(subreddits) do
-    search_str = "%#{str}%"
-
     from(c in __MODULE__,
       join: p in assoc(c, :post),
       join: s in assoc(p, :subreddit),
@@ -62,15 +60,15 @@ defmodule BdfrBrowser.Comment do
         post_title: p.title,
         post_date: fragment("to_char(?, 'YYYY-MM')", p.posted_at)
       },
-      where: ilike(c.body, ^search_str),
+      where:
+        fragment("? @@ websearch_to_tsquery('english', ?)", c.searchable_content, ^str) or
+          fragment("? @@ websearch_to_tsquery('german', ?)", c.searchable_content, ^str),
       order_by: [desc: c.posted_at],
       group_by: [c.id, p.id, s.name]
     )
   end
 
   def search(str, subreddits) when is_list(subreddits) do
-    search_str = "%#{str}%"
-
     from(c in __MODULE__,
       join: p in assoc(c, :post),
       join: s in assoc(p, :subreddit),
@@ -85,7 +83,10 @@ defmodule BdfrBrowser.Comment do
         post_title: p.title,
         post_date: fragment("to_char(?, 'YYYY-MM')", p.posted_at)
       },
-      where: s.name in ^subreddits and ilike(c.body, ^search_str),
+      where:
+        s.name in ^subreddits and
+          (fragment("? @@ websearch_to_tsquery('english', ?)", c.searchable_content, ^str) or
+             fragment("? @@ websearch_to_tsquery('german', ?)", c.searchable_content, ^str)),
       order_by: [desc: c.posted_at],
       group_by: [c.id, p.id, s.name]
     )

lib/bdfr_browser/post.ex

@@ -123,8 +123,6 @@ defmodule BdfrBrowser.Post do
   def search(str), do: search(str, nil)
 
   def search(str, subreddits) when is_nil(subreddits) do
-    search_str = "%#{str}%"
-
     from(p in __MODULE__,
       left_join: c in assoc(p, :comments),
       join: s in assoc(p, :subreddit),
@@ -137,15 +135,15 @@ defmodule BdfrBrowser.Post do
         subreddit: s.name,
         date: fragment("to_char(?, 'YYYY-MM')", p.posted_at)
       },
-      where: ilike(p.title, ^search_str) or ilike(p.selftext, ^search_str),
+      where:
+        fragment("? @@ websearch_to_tsquery('english', ?)", p.searchable_content, ^str) or
+          fragment("? @@ websearch_to_tsquery('german', ?)", p.searchable_content, ^str),
       order_by: [desc: p.posted_at],
       group_by: [p.id, s.name]
     )
   end
 
   def search(str, subreddits) when is_list(subreddits) do
-    search_str = "%#{str}%"
-
     from(p in __MODULE__,
       left_join: c in assoc(p, :comments),
       join: s in assoc(p, :subreddit),
@@ -158,7 +156,10 @@ defmodule BdfrBrowser.Post do
         subreddit: s.name,
         date: fragment("to_char(?, 'YYYY-MM')", p.posted_at)
       },
-      where: s.name in ^subreddits and (ilike(p.title, ^search_str) or ilike(p.selftext, ^search_str)),
+      where:
+        s.name in ^subreddits and
+          (fragment("? @@ websearch_to_tsquery('english', ?)", p.searchable_content, ^str) or
+             fragment("? @@ websearch_to_tsquery('german', ?)", p.searchable_content, ^str)),
       order_by: [desc: p.posted_at],
       group_by: [p.id, s.name]
     )

priv/repo/migrations/20231009190058_add_post_comment_fulltext_search.exs

@@ -0,0 +1,53 @@
+defmodule BdfrBrowser.Repo.Migrations.AddPostCommentFulltextSearch do
+  use Ecto.Migration
+
+  def up do
+    # Posts
+    execute """
+      ALTER TABLE posts 
+        ADD COLUMN searchable_content tsvector
+        GENERATED ALWAYS AS (
+          setweight(to_tsvector('english', coalesce(title, '')), 'A') ||
+          setweight(to_tsvector('german', coalesce(title, '')), 'A') ||
+          setweight(to_tsvector('english', coalesce(selftext, '')), 'B') ||
+          setweight(to_tsvector('german', coalesce(selftext, '')), 'B') ||
+          setweight(to_tsvector('simple', coalesce(author, '')), 'C')
+        ) STORED;
+    """
+
+    execute """
+      CREATE INDEX posts_searchable_content_index ON posts USING gin(searchable_content);
+    """
+
+    # Comments
+    execute """
+      ALTER TABLE comments 
+        ADD COLUMN searchable_content tsvector
+        GENERATED ALWAYS AS (
+          setweight(to_tsvector('english', coalesce(body, '')), 'A') ||
+          setweight(to_tsvector('german', coalesce(body, '')), 'A') ||
+          setweight(to_tsvector('simple', coalesce(author, '')), 'B')
+        ) STORED;
+    """
+
+    execute """
+      CREATE INDEX comments_searchable_content_index ON comments USING gin(searchable_content);
+    """
+  end
+
+  def down do
+    # Posts
+    drop index("posts", [:searchable_content])
+
+    alter table(:posts) do
+      remove :searchable_content
+    end
+
+    # Comments
+    drop index("comments", [:searchable_content])
+
+    alter table(:comments) do
+      remove :searchable_content
+    end
+  end
+end