store topic as a ltree

packages/api/src/entity/library_item.ts

@@ -208,7 +208,7 @@ export class LibraryItem {
   @Column('timestamptz')
   seenAt?: Date
 
-  @Column('text')
+  @Column('ltree')
   topic?: string
 
   @Column('timestamptz')

packages/db/migrations/0177.do.public_item.sql

@@ -79,11 +79,14 @@ CREATE INDEX public_item_interaction_public_item_id_idx ON omnivore.public_item_
 CREATE TRIGGER update_public_item_interactions_modtime BEFORE UPDATE ON omnivore.public_item_interactions FOR EACH ROW EXECUTE PROCEDURE update_updated_at_column();
 GRANT SELECT, INSERT, UPDATE ON omnivore.public_item_interactions TO omnivore_user;
 
+CREATE EXTENSION LTREE;
 
 ALTER TABLE omnivore.library_item 
-    ADD COLUMN seen_at timestamptz,
-    ADD COLUMN digested_at timestamptz,
-    ADD COLUMN topic TEXT,
+    ADD COLUMN seen_at TIMESTAMPTZ,
+    ADD COLUMN digested_at TIMESTAMPTZ,
+    ADD COLUMN topic LTREE,
     ADD COLUMN score FLOAT;
 
+CREATE INDEX library_item_topic_idx ON omnivore.library_item USING GIST (topic);
+
 COMMIT;

packages/db/migrations/0177.undo.public_item.sql

@@ -9,6 +9,8 @@ DROP TABLE omnivore.public_item_stats;
 DROP TABLE omnivore.public_item;
 DROP TABLE omnivore.public_item_source;
 
+DROP INDEX omnivore.library_item_topic_idx;
+
 ALTER TABLE omnivore.library_item 
     DROP COLUMN seen_at,
     DROP COLUMN digested_at,