Is there a reason why osm2pgsql produces negative osm_id values?

I am examining data imported into a PostGIS database with osm2pgsql and I have noticed some values in the osm_id (which I assume is unique) are negative. Is that ok?

osm2pgsql osm_id

asked 18 Jan '11, 13:28

Tomas Pajonk
191●8●8●17
accept rate: 0%

edited 21 Jan '11, 09:17

TomH ♦♦
3.2k●8●35●41

One Answer:

osm_id is only unique within element types in OSM database (but not in osm2pgsql schema, see the comment from pnorman below). So the same osm_id can apply to a node, a way and a relation. That's why osm2pgsql polygon table changes the sign of the relation id when it comes from relations and the original positive way id when it comes from simple closed ways.

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answered 18 Jan '11, 13:49

Pieren
9.7k●20●75●157
accept rate: 15%

edited 03 Jul '14, 12:12

Thank you.

(18 Jan '11, 17:00) Tomas Pajonk

More background Information is in Wiki http://wiki.openstreetmap.org/wiki/Osm2pgsql/schema#Processed_Data

(02 Apr '13, 14:13) geekQ

osm_id is not unique in osm2pgsql's tables. Long ways are split by osm2pgsql into multiple rows with the same osm_id and multipolygons with distinct areas are also split into multiple rows.

(29 Sep '13, 05:58) pnorman

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osm2pgsql ×224
osm_id ×6

question asked: 18 Jan '11, 13:28

question was seen: 8,063 times

last updated: 03 Jul '14, 12:12

Is there a reason why osm2pgsql produces negative osm_id values?

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