Initial version

migrations/data/001_init.sql

@@ -0,0 +1,8 @@
+CREATE TABLE jokes (
+    id SERIAL NOT NULL PRIMARY KEY,
+    joke_text TEXT NOT NULL
+);
+
+---- create above / drop below ----
+
+DROP TABLE jokes;

migrations/data/002_ts.sql

@@ -0,0 +1,5 @@
+ALTER TABLE jokes ADD COLUMN ts TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW();
+
+---- create above / drop below ----
+
+ALTER TABLE jokes DROP COLUMN ts;

migrations/data/003_nsfw.sql

@@ -0,0 +1,5 @@
+ALTER TABLE jokes ADD COLUMN nsfw BOOLEAN NOT NULL DEFAULT 'f';
+
+---- create above / drop below ----
+
+ALTER TABLE jokes DROP COLUMN nsfw;

migrations/data/004_votes.sql

@@ -0,0 +1,7 @@
+ALTER TABLE jokes ADD COLUMN up_votes INT NOT NULL DEFAULT 0;
+ALTER TABLE jokes ADD COLUMN down_votes INT NOT NULL DEFAULT 0;
+
+---- create above / drop below ----
+
+ALTER TABLE jokes DROP COLUMN up_votes;
+ALTER TABLE jokes DROP COLUMN down_votes;

migrations/migrations.go

@@ -0,0 +1,82 @@
+package migrations
+
+import (
+	"context"
+	"embed"
+	"fmt"
+	"io/fs"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/tern/v2/migrate"
+)
+
+const versionTable = "db_version"
+
+type Migrator struct {
+	migrator *migrate.Migrator
+}
+
+//go:embed data/*.sql
+var migrationFiles embed.FS
+
+func NewMigrator(dbDNS string) (Migrator, error) {
+
+	conn, err := pgx.Connect(context.Background(), dbDNS)
+	if err != nil {
+		return Migrator{}, err
+	}
+	migrator, err := migrate.NewMigratorEx(context.Background(), conn, versionTable, &migrate.MigratorOptions{
+		DisableTx: false,
+	})
+	if err != nil {
+		return Migrator{}, err
+	}
+
+	migrationRoot, _ := fs.Sub(migrationFiles, "data")
+
+	err = migrator.LoadMigrations(migrationRoot)
+	if err != nil {
+		return Migrator{}, err
+	}
+
+	return Migrator{
+		migrator: migrator,
+	}, nil
+}
+
+// Info the current migration version and the embedded maximum migration, and a textual
+// representation of the migration state for informational purposes.
+func (m Migrator) Info() (int32, int32, string, error) {
+
+	version, err := m.migrator.GetCurrentVersion(context.Background())
+	if err != nil {
+		return 0, 0, "", err
+	}
+	info := ""
+
+	var last int32
+	for _, thisMigration := range m.migrator.Migrations {
+		last = thisMigration.Sequence
+
+		cur := version == thisMigration.Sequence
+		indicator := "  "
+		if cur {
+			indicator = "->"
+		}
+		info = info + fmt.Sprintf("%2s %3d %s\n", indicator, thisMigration.Sequence, thisMigration.Name)
+	}
+
+	return version, last, info, nil
+}
+
+// Migrate migrates the DB to the most recent version of the schema.
+func (m Migrator) Migrate() error {
+	err := m.migrator.Migrate(context.Background())
+	return err
+}
+
+// MigrateTo migrates to a specific version of the schema. Use '0' to undo all migrations.
+func (m Migrator) MigrateTo(ver int32) error {
+	err := m.migrator.MigrateTo(context.Background(), ver)
+	return err
+}