add record size to hourly snapshot page

db/helpers.go

@@ -24,6 +24,48 @@ type ColumnDef struct {
 	Type string
 }
 
+// TableRowCount returns COUNT(*) for a table.
+func TableRowCount(ctx context.Context, dbConn *sqlx.DB, table string) (int64, error) {
+	if err := ValidateTableName(table); err != nil {
+		return 0, err
+	}
+	var count int64
+	query := fmt.Sprintf(`SELECT COUNT(*) FROM %s`, table)
+	if err := dbConn.GetContext(ctx, &count, query); err != nil {
+		return 0, err
+	}
+	return count, nil
+}
+
+// EnsureColumns adds the provided columns to a table if they are missing.
+func EnsureColumns(ctx context.Context, dbConn *sqlx.DB, tableName string, columns []ColumnDef) error {
+	if _, err := SafeTableName(tableName); err != nil {
+		return err
+	}
+	for _, column := range columns {
+		if err := AddColumnIfMissing(ctx, dbConn, tableName, column); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// AddColumnIfMissing performs a best-effort ALTER TABLE to add a column, ignoring "already exists".
+func AddColumnIfMissing(ctx context.Context, dbConn *sqlx.DB, tableName string, column ColumnDef) error {
+	if _, err := SafeTableName(tableName); err != nil {
+		return err
+	}
+	query := fmt.Sprintf(`ALTER TABLE %s ADD COLUMN "%s" %s`, tableName, column.Name, column.Type)
+	if _, err := dbConn.ExecContext(ctx, query); err != nil {
+		errText := strings.ToLower(err.Error())
+		if strings.Contains(errText, "duplicate column") || strings.Contains(errText, "already exists") {
+			return nil
+		}
+		return err
+	}
+	return nil
+}
+
 // ValidateTableName ensures table identifiers are safe for interpolation.
 func ValidateTableName(name string) error {
 	if name == "" {