separate lessons schema from practices in hierarchy

Replace rename-based lesson migration with additive sub_module_lessons creation, preserve sub_module_practices as its own model, and enforce QUIZ/PRACTICE filtering in hierarchy reads to prevent cross-mixing.

Made-with: Cursor

db/migrations/000031_rename_sub_module_practices_to_lessons.down.sql

@@ -1,6 +1,4 @@
-ALTER TABLE IF EXISTS sub_module_lessons
-RENAME TO sub_module_practices;
+DROP INDEX IF EXISTS idx_sub_module_lessons_sub_module_id;
 
-ALTER INDEX IF EXISTS idx_sub_module_lessons_sub_module_id
-RENAME TO idx_sub_module_practices_sub_module_id;
+DROP TABLE IF EXISTS sub_module_lessons;
 

db/migrations/000031_rename_sub_module_practices_to_lessons.up.sql

@@ -1,6 +1,15 @@
-ALTER TABLE IF EXISTS sub_module_practices
-RENAME TO sub_module_lessons;
+-- Keep practices as a separate feature and introduce lessons as a new table.
+CREATE TABLE IF NOT EXISTS sub_module_lessons (
+    id BIGSERIAL PRIMARY KEY,
+    sub_module_id BIGINT NOT NULL REFERENCES sub_modules(id) ON DELETE CASCADE,
+    question_set_id BIGINT NOT NULL REFERENCES question_sets(id) ON DELETE CASCADE,
+    intro_video_url TEXT,
+    display_order INT NOT NULL DEFAULT 0,
+    is_active BOOLEAN NOT NULL DEFAULT TRUE,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    UNIQUE(question_set_id)
+);
 
-ALTER INDEX IF EXISTS idx_sub_module_practices_sub_module_id
-RENAME TO idx_sub_module_lessons_sub_module_id;
+CREATE INDEX IF NOT EXISTS idx_sub_module_lessons_sub_module_id
+ON sub_module_lessons(sub_module_id);
 

db/migrations/000032_add_sub_module_practices.up.sql

@@ -12,6 +12,24 @@ CREATE TABLE IF NOT EXISTS sub_module_practices (
     UNIQUE(question_set_id)
 );
 
+-- If the table already existed from older unified hierarchy migrations,
+-- backfill missing columns so practices keep their own richer schema.
+ALTER TABLE sub_module_practices
+ADD COLUMN IF NOT EXISTS title VARCHAR(255);
+
+ALTER TABLE sub_module_practices
+ADD COLUMN IF NOT EXISTS description TEXT;
+
+ALTER TABLE sub_module_practices
+ADD COLUMN IF NOT EXISTS thumbnail TEXT;
+
+UPDATE sub_module_practices
+SET title = COALESCE(NULLIF(title, ''), 'Practice')
+WHERE title IS NULL OR title = '';
+
+ALTER TABLE sub_module_practices
+ALTER COLUMN title SET NOT NULL;
+
 CREATE INDEX IF NOT EXISTS idx_sub_module_practices_sub_module_id
 ON sub_module_practices(sub_module_id);
 

db/query/hierarchy.sql

@@ -57,6 +57,7 @@ FROM sub_module_lessons smp
 JOIN question_sets qs ON qs.id = smp.question_set_id
 WHERE smp.sub_module_id = $1
   AND smp.is_active = TRUE
+  AND qs.set_type = 'QUIZ'
 ORDER BY smp.display_order ASC, smp.id ASC;
 
 -- name: GetSubModulePractices :many
@@ -77,6 +78,7 @@ FROM sub_module_practices smp
 JOIN question_sets qs ON qs.id = smp.question_set_id
 WHERE smp.sub_module_id = $1
   AND smp.is_active = TRUE
+  AND qs.set_type = 'PRACTICE'
 ORDER BY smp.display_order ASC, smp.id ASC;
 
 -- name: GetFullHierarchyByCourseID :many

gen/db/hierarchy.sql.go

@@ -561,6 +561,7 @@ FROM sub_module_lessons smp
 JOIN question_sets qs ON qs.id = smp.question_set_id
 WHERE smp.sub_module_id = $1
   AND smp.is_active = TRUE
+  AND qs.set_type = 'QUIZ'
 ORDER BY smp.display_order ASC, smp.id ASC
 `
 
@@ -628,6 +629,7 @@ FROM sub_module_practices smp
 JOIN question_sets qs ON qs.id = smp.question_set_id
 WHERE smp.sub_module_id = $1
   AND smp.is_active = TRUE
+  AND qs.set_type = 'PRACTICE'
 ORDER BY smp.display_order ASC, smp.id ASC
 `