column "fid" specified more than once

[tjwebb]

I'm not able to import any layers that already have an FID field. I get the error column "fid" specified more than once when running import foreign schema

I think it's because of this:

pgsql-ogr-fdw/ogr_fdw_common.c

Line 311 in 45a2547

stringbuffer_append(buf, " fid bigint");

Shouldn't we only create this field if it doesn't exist already in the source data?

[pramsey]

We need a guaranteed unique integer key for GDAL, which expects such a key for all its sources. Every GDAL source in fact has an implicit key, which you access using API calls distinct from the regular column data access. We need a place to slot that extra "column" into our FDW table, and I chose, perhaps incorrectly to slot it into "fid". Perhaps ogr_fid would have been smarter (@robe2 ?)

[tjwebb]

Well, I've seen ogr_fid in external sources also, occasionally.

One approach might be to support an except clause for columns the same way you currently do with layer names? This would allow me to solve this problem, and also could be useful for other situations as well.

[tjwebb]

Related to #103 and #152