Can't use multipolygon as column type using flex

[SidereusNox]

I have a lua script I use to transform data and load it into the database. In my database, I would like to have a table osm_boundary with multipolygons:

tables.osm_boundary = osm2pgsql.define_table{
    name = "osm_boundary",
    ids = { type = 'area', id_column = 'osm_id'},
    columns = {
        { column = 'osm_version', type = 'integer'},
        { column = 'osm_timestamp', type = 'timestamptz'},
        { column = 'name', type = 'text' },
        { column = 'label', type = 'text' },
        { column = 'tags', type = 'hstore' },
        { column = 'geom', type = 'multipolygon' }
    }
} 

while processing relations, I search for relations with type=multipolygons with the tag boundary and try to add them into my table. In the future I also want to expand my search by relations with type=boundary. In the documentation it is stated, that in order to keep polygons as multipolygons I need to add a multi parameter to the transformation.

    local type = object.tags.type

    if (type == 'multipolygon' and object.tags.boundary) then

        tables.osm_boundary:add_row({
            osm_version = version,
            osm_timestamp = getTimestamp(object.timestamp),
            name = object.tags.name,
            label = label,
            tags = object.tags,
            geom = { create = 'area', multi = true }
        })
        return
    end

Starting osm2pgsql with this script leads to the following output:

b'osm2pgsql version 1.3.0 (1.3.0)\n\nAllocating memory for dense node cache\nAllocating dense node cache in one big chunk\nAllocating memory for sparse node cache\nSharing dense sparse\nNode-cache: cache=800MB, maxblocks=12800*65536, allocation method=11\nMid: pgsql, cache=800\nSetting up table: planet_osm_nodes\nSetting up table: planet_osm_ways\nSetting up table: planet_osm_rels\nUsing projection SRS 4326 (Latlong)\n\nReading in file: /data/all-countries.osm.pbf\nUsing PBF parser.\n\rProcessing: Node(50k 50.0k/s) Way(0k 0.00k/s) Relation(0 0.0/s)\rProcessing: Node(283k 141.5k/s) Way(1k 1.00k/s) Relation(0 0.0/s)\rProcessing: Node(283k 141.5k/s) Way(22k 22.00k/s) Relation(0 0.0/s)\rProcessing: Node(283k 141.5k/s) Way(28k 28.00k/s) Relation(849 849.0/s)  parse time: 3s\nNode stats: total(283696), max(8084224264) in 2s\nWay stats: total(28040), max(867264596) in 1s\nRelation stats: total(849), max(11559074) in 0s\nresult COPY END for osm_boundary failed: ERROR:  Geometry type (Polygon) does not match column type (MultiPolygon)\nCONTEXT:  COPY osm_boundary, line 1, column geom: "0103000020E6100000010000000B00000075988AE83244234013A8B4B4098B4740AFAA03C534442340157A5803EF8A47408F..."\n\nDB copy thread failed: Ending COPY mode\nNo marked ways (Skipping stage 2).\n'

with the error

ERROR:  Geometry type (Polygon) does not match column type (MultiPolygon)\nCONTEXT:  COPY osm_boundary, line 1, column geom: 

and an empty table:

select * from osm_boundary;
 osm_id | osm_version | osm_timestamp | name | label | tags | admin_level | geom 
--------+-------------+---------------+------+-------+------+-------------+------
(0 rows)

Pleas help me get a Solution. Thank you in advance

[joto]

The problem ist that, despite their name in OSM, multipolygon relations can still create polygon geometries. If multi is set to true, it only means that multipolygon geometries are not split, it doesn't mean non-multi polygons are output as multi-polygons. So this means you will have polygons and multipolygons in that column and you need to set the column type to geometry:

{ column = 'geom', type = 'geometry' }

The documentation is misleading and maybe even wrong there and I will correct that.

[joto]

I believe the documentation is much clearer now. (Note that the behaviour has also changed, see the manual.)