Querying GAIA DR2 for Polaris (for example using https://gea.esac.esa.int/archive/) yields empty parallax columns. Anyone knows why it was not measured/published?
My query for stars north of +75° and brighter than magnitude 4 returns only 6 stars, brightest of which is γ Cephei. Polaris may be too bright for Gaia. Even if it doesn't saturate the detector, a bright star will probably have larger astrometric errors than a star between magnitudes 6 and 12. DR2 coverage of magnitude 5 and brighter stars is better than DR1 but still rather sparse. Section 3.1 of this paper plots parallax coverage vs. magnitude and explains why some stars have positions but not parallaxes.