PostGIS Geometry type not matching column type in QGIS

Yes, you can tell PostGIS to accept any geometry type (polygon, multipolygon, point, linestring, etc) by adding the following constraint to your table.

For PostGIS 2.x (using generic Geometry typemod)

ALTER TABLE my_table ALTER COLUMN geom TYPE geometry(Geometry,4326);

Previous Answer (for PostGIS 1.x using Constraints)

CONSTRAINT enforce_geometry_type CHECK (geometrytype(geom) = 'MULTIPOLYGON'::text OR geometrytype(geom) = 'POLYGON'::text OR geom IS NULL)

This appears to be a known issue that won't be fixed: see http://hub.qgis.org/issues/5328

If you need a workaround, try changing your table's geometry column type to a generic 'geometry':

ALTER TABLE my_table ALTER COLUMN geom SET DATA TYPE geometry;

After you've done your import, you can revert back to MultiPolygon:

ALTER TABLE my_table ALTER COLUMN geom 
    SET DATA TYPE geometry(MultiPolygon) USING ST_Multi(geom);

Alternatively, try loading your data using ogr2ogr.

Although I did try to solve it with "Import to PostGis" algorithm, I didn't success (my database wasn't appearing on the list - I am using QGIS 2.10).

Instead, I used shp2pgsql, which was a simple Command Prompt task as described below:

• Open Command Prompt (as administrator)
• Get to PostgreSQL/bin folder which should look something like this: C:Program FilesPostgreSQL9.4bin>
• Simply copy & paste your .shp files to this directory. ( I copied my entire folder with my .shp files.
• On Command Prompt type the following: shp2pgsql -s 4326 MyShpDir/MySHPFile.shp> MYSQLFile.sql where MyShpDir your directory, 4326 is WGS84's SRID so change if you are using different SSID, MySHPFile.shp your particular file (MYSQLFile will be created automatically). Obviously do this for all of the files you want to convert. The files will be saved in your current directory (C:Program FilesPostgreSQL9.4bin in my case)

Then simply copy & paste the SQL files in your PLSQL DataBase.

Moreover, one additional cool thing about shp2pgsql is the fact that you can instantly create an index in your table by just adding the I parameter in the command, like this:

shp2pgsql -s 4326 -I MyShpDir/MySHPFile.shp> MYSQLFile.sql

I use ogr2ogr to automate ingest of shapefiles into a PostGIS database. Specifically with regard to the question, use the option:

-nlt PROMOTE_TO_MULTI

This will force ogr2ogr to promote POLYGON geometries to MULTIPOLYGON, avoiding the error. A very simple example:

ogr2ogr -f "PostgreSQL" PG:"dbname='<my_db>'" -nlt PROMOTE_TO_MULTI <shapefile>

I have omitted pgsql host/auth details. To batch multiple shapefiles you might do something like:

find ./ -name *.shp | xargs -n1 ogr2ogr <ogr2ogr args omitting the shapefile>

I tried the 'Import into PostGIS' algorithm solution but found that that did not work either. The easiest solution I found was to go to Database > DB Manager, navigate to your database, and click the Import layer/file (the down arrow) button.