internal/store/migrate.go

@@ -35,6 +35,75 @@ CREATE UNIQUE INDEX IF NOT EXISTS users_email_lower_uidx
 	return nil
 }
 
+// migratePosts creates the unified post model and snapshots legacy content.
+// Legacy tables remain in place until the application cutover is complete.
+func migratePosts(ctx context.Context, exec execContext) error {
+	steps := []struct {
+		name string
+		sql  string
+	}{
+		{"create posts", `
+CREATE TABLE IF NOT EXISTS posts (
+  id TEXT PRIMARY KEY,
+  parent_id TEXT REFERENCES posts(id) ON DELETE CASCADE,
+  author_id TEXT NOT NULL REFERENCES users(id),
+  title TEXT NOT NULL DEFAULT '',
+  body TEXT NOT NULL,
+  city TEXT NOT NULL DEFAULT '',
+  post_date TEXT NOT NULL DEFAULT '',
+  hidden INTEGER NOT NULL DEFAULT 0,
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL,
+  CHECK (
+    (parent_id IS NULL AND title <> '' AND post_date <> '')
+    OR
+    (parent_id IS NOT NULL AND title = '' AND city = '' AND post_date = '' AND hidden = 0)
+  )
+)`},
+		{"index post replies", `
+CREATE INDEX IF NOT EXISTS idx_posts_parent_created
+  ON posts(parent_id, created_at, id)`},
+		{"index root posts", `
+CREATE INDEX IF NOT EXISTS idx_posts_root_date
+  ON posts(post_date, hidden)
+  WHERE parent_id IS NULL`},
+		{"create post votes", `
+CREATE TABLE IF NOT EXISTS post_votes (
+  user_id TEXT NOT NULL REFERENCES users(id),
+  post_id TEXT NOT NULL REFERENCES posts(id) ON DELETE CASCADE,
+  value INTEGER NOT NULL CHECK (value IN (-1, 1)),
+  PRIMARY KEY (user_id, post_id)
+)`},
+		{"copy questions", `
+INSERT INTO posts (
+  id, parent_id, author_id, title, body, city, post_date, hidden, created_at, updated_at
+)
+SELECT
+  id, NULL, author_id, title, body, city, hunt_date, hidden, created_at, created_at
+FROM questions
+ON CONFLICT (id) DO NOTHING`},
+		{"copy answers", `
+INSERT INTO posts (
+  id, parent_id, author_id, title, body, city, post_date, hidden, created_at, updated_at
+)
+SELECT
+  'answer:' || question_id, question_id, author_id, '', body, '', '', 0, created_at, updated_at
+FROM answers
+ON CONFLICT (id) DO NOTHING`},
+		{"copy votes", `
+INSERT INTO post_votes (user_id, post_id, value)
+SELECT user_id, question_id, value
+FROM votes
+ON CONFLICT (user_id, post_id) DO NOTHING`},
+	}
+	for _, step := range steps {
+		if _, err := exec.ExecContext(ctx, step.sql); err != nil {
+			return fmt.Errorf("%s: %w", step.name, err)
+		}
+	}
+	return nil
+}
+
 type execContext interface {
 	ExecContext(ctx context.Context, query string, args ...any) (sql.Result, error)
 	QueryContext(ctx context.Context, query string, args ...any) (*sql.Rows, error)
@@ -81,6 +150,7 @@ CREATE TABLE IF NOT EXISTS schema_migrations (
 		}},
 		{"002_user_profile_columns", migrateUserProfileColumns},
 		{"003_user_email", migrateUserEmail},
+		{"004_posts", migratePosts},
 	}
 	for _, m := range migrations {
 		if applied[m.version] {

internal/store/migrate_posts_test.go

@@ -0,0 +1,213 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/google/uuid"
+)
+
+func TestMigratePostsCopiesLegacyData(t *testing.T) {
+	rawURL := strings.TrimSpace(os.Getenv("TEST_DATABASE_URL"))
+	if rawURL == "" {
+		t.Skip("TEST_DATABASE_URL is not set")
+	}
+	dsn, err := postgresDSN(rawURL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	ctx := context.Background()
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+
+	schemaName := "test_posts_" + strings.ReplaceAll(uuid.NewString(), "-", "")
+	if _, err := conn.ExecContext(ctx, "CREATE SCHEMA "+schemaName); err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		_, _ = conn.ExecContext(context.Background(), "SET search_path TO public")
+		_, _ = conn.ExecContext(context.Background(), "DROP SCHEMA "+schemaName+" CASCADE")
+	}()
+	if _, err := conn.ExecContext(ctx, "SET search_path TO "+schemaName); err != nil {
+		t.Fatal(err)
+	}
+
+	legacySchema := `
+CREATE TABLE users (
+  id TEXT PRIMARY KEY
+);
+CREATE TABLE questions (
+  id TEXT PRIMARY KEY,
+  author_id TEXT NOT NULL REFERENCES users(id),
+  title TEXT NOT NULL,
+  body TEXT NOT NULL,
+  city TEXT NOT NULL DEFAULT '',
+  hunt_date TEXT NOT NULL,
+  hidden INTEGER NOT NULL DEFAULT 0,
+  created_at TEXT NOT NULL
+);
+CREATE TABLE answers (
+  question_id TEXT PRIMARY KEY REFERENCES questions(id) ON DELETE CASCADE,
+  author_id TEXT NOT NULL REFERENCES users(id),
+  body TEXT NOT NULL,
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL
+);
+CREATE TABLE votes (
+  user_id TEXT NOT NULL REFERENCES users(id),
+  question_id TEXT NOT NULL REFERENCES questions(id) ON DELETE CASCADE,
+  value INTEGER NOT NULL CHECK (value IN (-1, 1)),
+  PRIMARY KEY (user_id, question_id)
+);`
+	if err := applySchema(ctx, conn, legacySchema); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := conn.ExecContext(ctx, `
+INSERT INTO users (id) VALUES ('homeowner'), ('plumber');
+INSERT INTO questions (id, author_id, title, body, city, hunt_date, hidden, created_at)
+VALUES ('question-1', 'homeowner', 'Leaky sink', 'It drips.', 'Oakland', '2026-08-26', 0, '2026-08-26T08:00:00Z');
+INSERT INTO answers (question_id, author_id, body, created_at, updated_at)
+VALUES ('question-1', 'plumber', 'Replace the cartridge.', '2026-08-26T09:00:00Z', '2026-08-26T09:05:00Z');
+INSERT INTO votes (user_id, question_id, value)
+VALUES ('homeowner', 'question-1', 1);`); err != nil {
+		t.Fatal(err)
+	}
+
+	if err := migratePosts(ctx, conn); err != nil {
+		t.Fatal(err)
+	}
+	if err := migratePosts(ctx, conn); err != nil {
+		t.Fatalf("migration is not idempotent: %v", err)
+	}
+
+	var postCount, voteCount, legacyQuestionCount, legacyAnswerCount int
+	if err := conn.QueryRowContext(ctx, "SELECT count(*) FROM posts").Scan(&postCount); err != nil {
+		t.Fatal(err)
+	}
+	if err := conn.QueryRowContext(ctx, "SELECT count(*) FROM post_votes").Scan(&voteCount); err != nil {
+		t.Fatal(err)
+	}
+	if err := conn.QueryRowContext(ctx, "SELECT count(*) FROM questions").Scan(&legacyQuestionCount); err != nil {
+		t.Fatal(err)
+	}
+	if err := conn.QueryRowContext(ctx, "SELECT count(*) FROM answers").Scan(&legacyAnswerCount); err != nil {
+		t.Fatal(err)
+	}
+	if postCount != 2 || voteCount != 1 || legacyQuestionCount != 1 || legacyAnswerCount != 1 {
+		t.Fatalf(
+			"counts posts=%d votes=%d legacy questions=%d answers=%d",
+			postCount,
+			voteCount,
+			legacyQuestionCount,
+			legacyAnswerCount,
+		)
+	}
+
+	var rootParent sql.NullString
+	var rootAuthor, title, rootBody, city, postDate, rootCreated, rootUpdated string
+	if err := conn.QueryRowContext(ctx, `
+SELECT parent_id, author_id, title, body, city, post_date, created_at, updated_at
+FROM posts
+WHERE id = 'question-1'`).Scan(
+		&rootParent,
+		&rootAuthor,
+		&title,
+		&rootBody,
+		&city,
+		&postDate,
+		&rootCreated,
+		&rootUpdated,
+	); err != nil {
+		t.Fatal(err)
+	}
+	if rootParent.Valid ||
+		rootAuthor != "homeowner" ||
+		title != "Leaky sink" ||
+		rootBody != "It drips." ||
+		city != "Oakland" ||
+		postDate != "2026-08-26" ||
+		rootCreated != "2026-08-26T08:00:00Z" ||
+		rootUpdated != rootCreated {
+		t.Fatalf("unexpected root post")
+	}
+
+	var replyParent, replyAuthor, replyBody, replyCreated, replyUpdated string
+	if err := conn.QueryRowContext(ctx, `
+SELECT parent_id, author_id, body, created_at, updated_at
+FROM posts
+WHERE id = 'answer:question-1'`).Scan(
+		&replyParent,
+		&replyAuthor,
+		&replyBody,
+		&replyCreated,
+		&replyUpdated,
+	); err != nil {
+		t.Fatal(err)
+	}
+	if replyParent != "question-1" ||
+		replyAuthor != "plumber" ||
+		replyBody != "Replace the cartridge." ||
+		replyCreated != "2026-08-26T09:00:00Z" ||
+		replyUpdated != "2026-08-26T09:05:00Z" {
+		t.Fatalf("unexpected reply post")
+	}
+
+	var voteValue int
+	if err := conn.QueryRowContext(ctx, `
+SELECT value FROM post_votes
+WHERE user_id = 'homeowner' AND post_id = 'question-1'`).Scan(&voteValue); err != nil {
+		t.Fatal(err)
+	}
+	if voteValue != 1 {
+		t.Fatalf("vote value = %d, want 1", voteValue)
+	}
+
+	if _, err := conn.ExecContext(ctx, `
+INSERT INTO posts (
+  id, parent_id, author_id, title, body, city, post_date, hidden, created_at, updated_at
+) VALUES (
+  'invalid-reply', 'question-1', 'homeowner', 'Replies cannot have titles', 'Body', '', '', 0, 'now', 'now'
+)`); err == nil {
+		t.Fatal("reply with root-only title unexpectedly succeeded")
+	}
+}
+
+func TestMigratePostsReportsStep(t *testing.T) {
+	t.Parallel()
+
+	exec := &failingMigrationExec{failAt: 5}
+	err := migratePosts(context.Background(), exec)
+	if err == nil || !strings.Contains(err.Error(), "copy questions") {
+		t.Fatalf("error = %v, want copy questions context", err)
+	}
+}
+
+type failingMigrationExec struct {
+	calls  int
+	failAt int
+}
+
+func (f *failingMigrationExec) ExecContext(context.Context, string, ...any) (sql.Result, error) {
+	f.calls++
+	if f.calls == f.failAt {
+		return nil, fmt.Errorf("boom")
+	}
+	return nil, nil
+}
+
+func (*failingMigrationExec) QueryContext(context.Context, string, ...any) (*sql.Rows, error) {
+	return nil, fmt.Errorf("not implemented")
+}

internal/store/sqlc/models.go

@@ -5,6 +5,7 @@
 package sqlc
 
 import (
+	"database/sql"
 	"time"
 )
 
@@ -16,6 +17,25 @@ type Answer struct {
 	UpdatedAt  string
 }
 
+type Post struct {
+	ID        string
+	ParentID  sql.NullString
+	AuthorID  string
+	Title     string
+	Body      string
+	City      string
+	PostDate  string
+	Hidden    int32
+	CreatedAt string
+	UpdatedAt string
+}
+
+type PostVote struct {
+	UserID string
+	PostID string
+	Value  int32
+}
+
 type Question struct {
 	ID        string
 	AuthorID  string

schema.sql

@@ -42,6 +42,38 @@ CREATE TABLE IF NOT EXISTS answers (
   updated_at TEXT NOT NULL
 );
 
+CREATE TABLE IF NOT EXISTS posts (
+  id TEXT PRIMARY KEY,
+  parent_id TEXT REFERENCES posts(id) ON DELETE CASCADE,
+  author_id TEXT NOT NULL REFERENCES users(id),
+  title TEXT NOT NULL DEFAULT '',
+  body TEXT NOT NULL,
+  city TEXT NOT NULL DEFAULT '',
+  post_date TEXT NOT NULL DEFAULT '',
+  hidden INTEGER NOT NULL DEFAULT 0,
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL,
+  CHECK (
+    (parent_id IS NULL AND title <> '' AND post_date <> '')
+    OR
+    (parent_id IS NOT NULL AND title = '' AND city = '' AND post_date = '' AND hidden = 0)
+  )
+);
+
+CREATE INDEX IF NOT EXISTS idx_posts_parent_created
+  ON posts(parent_id, created_at, id);
+
+CREATE INDEX IF NOT EXISTS idx_posts_root_date
+  ON posts(post_date, hidden)
+  WHERE parent_id IS NULL;
+
+CREATE TABLE IF NOT EXISTS post_votes (
+  user_id TEXT NOT NULL REFERENCES users(id),
+  post_id TEXT NOT NULL REFERENCES posts(id) ON DELETE CASCADE,
+  value INTEGER NOT NULL CHECK (value IN (-1, 1)),
+  PRIMARY KEY (user_id, post_id)
+);
+
 CREATE TABLE IF NOT EXISTS sessions (
   token TEXT PRIMARY KEY,
   data BYTEA NOT NULL,