For exporting GIS shapefile to a postgresql database we can use ogr2ogr command, example:
ogr2ogr -t_srs EPSG:3857 -f PostgreSQL “PG:dbname=databasename user=databaseuser” test.shp
In example above we export (test.shp) to database: “databasename“ with a dbuser: “databaseuser” with SRID= EPSG:3857
For exporting a geojson file into Postgis
ogr2ogr -f “PostgreSQL” PG:”PG:dbname=databasename user=databaseuser” “test.geojson”
In example above we export (test.geojson) to database: “databasename“ with a dbuser: “databaseuser”