Andrew Dunstan wrote:

Bruce Momjian said:

Second, I found a problem with NULLs.  If I do:
      test=> create table test (x text, y text);
      test=> insert into test values ('', NULL);
      INSERT 17221 1

then this:

test=> copy test to '/tmp/b' with csv;



and this:

test=> copy test to '/tmp/b' with csv NULL 'fred';



Is that logical? A non-null field went from "" to nothing.

One more point about this - we can't force quoting of every non-null value, which would remove the "inconsistency" you see here, because spreadsheets especially infer information from whether or not a CSV value is quoted. In particular, they will not usually treat a quoted numeric value as numeric, which would be a very undesirable effect.

Thinking about this some more .... maybe the right rule would be "quote all non-numeric non-null values". That would fix the odd effect that Bruce saw, and it would also stop a spreadsheet from interpreting a date like 2002-03-04 as an arithmetic expression.

Note that we don't care if a value is quoted or not - the only inference we draw from it is that if it is quoted it can't be null. We don't need to draw type inferences from it because we know the type we are trying to import into from the table defn. This fits nicely with the rule about being liberal with what you accept.




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