Proposal: Add path column to categories table as ltree type to make tree traversing easier

.gitignore

@@ -1,5 +1,6 @@
 /target
 .cargo
+.vscode/
 
 # compiled output
 /dist
@@ -21,3 +22,5 @@ yarn-error.log
 testem.log
 .env
 docker-compose.override.yml
+*~
+

Cargo.toml

@@ -47,6 +47,7 @@ dotenv = "0.11.0"
 toml = "0.4"
 diesel = { version = "1.3.0", features = ["postgres", "serde_json", "chrono", "r2d2"] }
 diesel_full_text_search = "1.0.0"
+diesel_ltree = "0.1.3"
 serde_json = "1.0.0"
 serde_derive = "1.0.0"
 serde = "1.0.0"

app/models/category.js

@@ -8,6 +8,7 @@ export default DS.Model.extend({
     crates_cnt: DS.attr('number'),
 
     subcategories: DS.attr(),
+    parent_categories: DS.attr(),
 
     crates: DS.hasMany('crate', { async: true }),
 });

app/templates/category/index.hbs

@@ -1,8 +1,11 @@
 {{ title category.category ' - Categories' }}
 
 <div id='crates-heading'>
-    {{svg-jar "crate"}}
-    <h1>{{ category.category }}</h1>
+    {{#link-to "categories" (html-attributes aria-label="Categories")}}{{svg-jar "crate"}}{{/link-to}}
+    <h1>
+        {{#each category.parent_categories as |parent|}}{{link-to parent.category "category" parent.slug}}::{{/each}}
+        {{~ category.category }}
+    </h1>
 </div>
 
 <div>

diesel.toml

@@ -3,5 +3,5 @@
 [print_schema]
 file = "src/schema.rs"
 with_docs = true
-import_types = ["diesel::sql_types::*", "diesel_full_text_search::{TsVector as Tsvector}"]
+import_types = ["diesel::sql_types::*", "diesel_full_text_search::{TsVector as Tsvector}", "diesel_ltree::Ltree"]
 patch_file = "src/schema.patch"

migrations/2017-10-08-193512_category_trees/down.sql

@@ -0,0 +1,14 @@
+-- This file should undo anything in `up.sql`
+DROP TRIGGER set_category_path_update ON categories;
+
+DROP TRIGGER set_category_path_insert ON categories;
+
+DROP FUNCTION IF EXISTS set_category_path_to_slug();
+
+DROP INDEX path_categories_idx;
+DROP INDEX path_gist_categories_idx;
+
+ALTER TABLE categories
+    DROP COLUMN path;
+
+DROP EXTENSION ltree;

migrations/2017-10-08-193512_category_trees/up.sql

@@ -0,0 +1,40 @@
+-- Your SQL goes here
+CREATE EXTENSION ltree;
+
+-- Create the new column which will represent our category tree.
+-- Fill it with values from `slug` column and then set to non-null
+ALTER TABLE categories
+    ADD COLUMN path ltree;
+
+-- Unfortunately, hyphens (dashes) are not allowed...
+UPDATE categories
+    SET path =  text2ltree('root.' || trim(replace(replace(slug, '-', '_'), '::', '.')))
+    WHERE path is NULL;
+
+ALTER TABLE CATEGORIES
+    ALTER COLUMN path SET NOT NULL;
+
+-- Create some indices that allow us to use GIST operators: '@>', etc
+CREATE INDEX path_gist_categories_idx ON categories USING GIST(path);
+CREATE INDEX path_categories_idx ON categories USING btree(path);
+
+-- Create procedure and trigger to auto-update path
+CREATE OR REPLACE FUNCTION set_category_path_to_slug()
+  RETURNS trigger AS
+    $BODY$
+BEGIN
+ NEW.path = text2ltree('root.' || trim(replace(replace(NEW.slug, '-', '_'), '::', '.')));
+ RETURN NEW;
+END;
+    $BODY$ LANGUAGE plpgsql;
+
+CREATE TRIGGER set_category_path_insert
+  BEFORE INSERT
+  ON categories
+  FOR EACH ROW
+  EXECUTE PROCEDURE set_category_path_to_slug();
+
+CREATE TRIGGER set_category_path_update
+  BEFORE UPDATE OF slug ON categories
+  FOR EACH ROW
+  EXECUTE PROCEDURE set_category_path_to_slug();