Metallicity vs. H I column density. Typical QSO-DLAs with metallicities from the literature (De Cia et al. 2018) are displayed as grey crosses. The sample of GRB-DLAs from Bolmer et al. (2019) is shown with green squares, and the remarkable GRB 080607 presented in Prochaska et al. (2009) is marked with a green upward-facing triangle. A sample of dusty (A_V >  0.1 mag, compiled by Heintz et al. 2018a) QSO-DLAs is shown with blue circles. The dashed line corresponds to a fixed metal column density, i.e. log N(X) = log N(H I) + [X/H] = 20.5 (see also Boissé et al. 1998). The ES-DLA towards GQ 1218+0832 studied here is marked with a red square, indicating the lower limit on the metallicity. It is one of the most metal-rich ES-DLAs discovered to date.