Re: BUG #6463: tables can have at most 1600 columns

> I drop a column but Postgresql still shows old (deleted) columns...

> My Java program does this:
> drop a boolean column and then add same column (with same name and
> specification), in dozens times, because updating (this) column is very slow
> !!!
> AND finally it says "tables can have at most 1600 columns"

Sorry, this is not a bug, or at least we're not going to fix it.
The fact that DROP COLUMN doesn't physically remove the column is an
intentional design decision. If we didn't do it that way, dropping
a column would require rewriting the entire table (and all its indexes)
and so would be horribly slow.

Perhaps if you discussed why you think that repeatedly dropping and
re-adding a column is a useful thing to do, we could help you find
another way. The bugs list is not the place for that discussion,
however.

regards, tom lane