ST_ScaleX — Returns the X component of the pixel width in units of coordinate reference system.
float8 ST_ScaleX(raster rast);
Returns the X component of the pixel width in units of coordinate reference system. Refer to World File for more details.
Changed: 2.0.0. In WKTRaster versions this was called ST_PixelSizeX.
SELECT rid, ST_ScaleX(rast) As rastpixwidth
FROM dummy_rast;
rid | rastpixwidth
-----+--------------
1 | 2
2 | 0.05