wip

sqliteutil/README.md

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+# sqliteutil
+
+## Transactions
+
+Simplify postgres transactions using `WithTx` for serializable transactions,
+or `WithTxDefault` for the default isolation level. Use the `SerialTxRunner`
+type to get automatic retries of serialization errors.
+
+## Migrations
+
+Put your migrations into a directory, for example `migrations`, ordered by name
+(YYYY-MM-DD prefix, for example). Embed the directory and pass it to the
+`Migrate` function:
+
+```Go
+//go:embed migrations
+var migrations embed.FS
+
+func init() {
+    Migrate(db, migrations) // Check the error, of course.
+}
+```
+
+## Testing
+
+In order to test this packge, we need to create a test user and database:
+
+```
+sudo su postgres
+psql
+
+CREATE DATABASE test;
+CREATE USER test WITH ENCRYPTED PASSWORD 'test';
+GRANT ALL PRIVILEGES ON DATABASE test TO test;
+
+use test
+
+GRANT ALL ON SCHEMA public TO test;
+```
+
+Check that you can connect via the command line:
+
+```
+psql -h 127.0.0.1 -U test --password test
+```

sqliteutil/go.mod

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+module git.crumpington.com/lib/sqliteutil
+
+go 1.23.2
+
+require github.com/mattn/go-sqlite3 v1.14.24 // indirect

sqliteutil/go.sum

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+github.com/mattn/go-sqlite3 v1.14.24 h1:tpSp2G2KyMnnQu99ngJ47EIkWVmliIizyZBfPrBWDRM=
+github.com/mattn/go-sqlite3 v1.14.24/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=

sqliteutil/migrate.go

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+package sqliteutil
+
+import (
+	"database/sql"
+	"embed"
+	"errors"
+	"fmt"
+	"path/filepath"
+	"sort"
+)
+
+const initMigrationTableQuery = `
+CREATE TABLE IF NOT EXISTS migrations(filename TEXT NOT NULL PRIMARY KEY);`
+
+const insertMigrationQuery = `INSERT INTO migrations(filename) VALUES($1)`
+
+const checkMigrationAppliedQuery = `SELECT EXISTS(SELECT 1 FROM migrations WHERE filename=$1)`
+
+func Migrate(db *sql.DB, migrationFS embed.FS) error {
+	return WithTx(db, func(tx *sql.Tx) error {
+		if _, err := tx.Exec(initMigrationTableQuery); err != nil {
+			return err
+		}
+
+		dirs, err := migrationFS.ReadDir(".")
+		if err != nil {
+			return err
+		}
+		if len(dirs) != 1 {
+			return errors.New("expected a single migrations directory")
+		}
+
+		if !dirs[0].IsDir() {
+			return fmt.Errorf("unexpected non-directory in migration FS: %s", dirs[0].Name())
+		}
+
+		dirName := dirs[0].Name()
+		files, err := migrationFS.ReadDir(dirName)
+		if err != nil {
+			return err
+		}
+
+		// Sort sql files by name.
+		sort.Slice(files, func(i, j int) bool {
+			return files[i].Name() < files[j].Name()
+		})
+
+		for _, dirEnt := range files {
+			if !dirEnt.Type().IsRegular() {
+				return fmt.Errorf("unexpected non-regular file in migration fs: %s", dirEnt.Name())
+			}
+
+			var (
+				name   = dirEnt.Name()
+				exists bool
+			)
+
+			err := tx.QueryRow(checkMigrationAppliedQuery, name).Scan(&exists)
+			if err != nil {
+				return err
+			}
+
+			if exists {
+				continue
+			}
+
+			migration, err := migrationFS.ReadFile(filepath.Join(dirName, name))
+			if err != nil {
+				return err
+			}
+
+			if _, err := tx.Exec(string(migration)); err != nil {
+				return fmt.Errorf("migration %s failed: %v", name, err)
+			}
+
+			if _, err := tx.Exec(insertMigrationQuery, name); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+}

sqliteutil/migrate_test.go

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+package sqliteutil
+
+import (
+	"database/sql"
+	"embed"
+	"testing"
+)
+
+//go:embed test-migrations
+var testMigrationFS embed.FS
+
+func TestMigrate(t *testing.T) {
+	db, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := Migrate(db, testMigrationFS); err != nil {
+		t.Fatal(err)
+	}
+
+	// Shouldn't have any effect.
+	if err := Migrate(db, testMigrationFS); err != nil {
+		t.Fatal(err)
+	}
+
+	query := `SELECT EXISTS(SELECT 1 FROM users WHERE UserID=$1)`
+	var exists bool
+
+	if err = db.QueryRow(query, 1).Scan(&exists); err != nil {
+		t.Fatal(err)
+	}
+	if exists {
+		t.Fatal("1 shouldn't exist")
+	}
+
+	if err = db.QueryRow(query, 2).Scan(&exists); err != nil {
+		t.Fatal(err)
+	}
+	if !exists {
+		t.Fatal("2 should exist")
+	}
+
+}

sqliteutil/test-migrations/000.sql

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+CREATE TABLE users(
+       UserID BIGINT NOT NULL PRIMARY KEY,
+       Email  TEXT   NOT NULL UNIQUE);
+
+CREATE TABLE user_notes(
+       UserID BIGINT NOT NULL REFERENCES users(UserID),
+       NoteID BIGINT NOT NULL,
+       Note   Text   NOT NULL,
+       PRIMARY KEY(UserID,NoteID));

sqliteutil/test-migrations/001.sql

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+INSERT INTO users(UserID, Email) VALUES (1, 'a@b.com'), (2, 'c@d.com');

sqliteutil/test-migrations/002.sql

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+DELETE FROM users WHERE UserID=1;

sqliteutil/tx.go

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+package sqliteutil
+
+import (
+	"database/sql"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+// This is a convenience function to run a function within a transaction.
+func WithTx(db *sql.DB, fn func(*sql.Tx) error) error {
+	// Start a transaction.
+	tx, err := db.Begin()
+	if err != nil {
+		return err
+	}
+
+	err = fn(tx)
+
+	if err == nil {
+		err = tx.Commit()
+	}
+
+	if err != nil {
+		_ = tx.Rollback()
+	}
+
+	return err
+}