Bug：Create a table with 1600 fields (reaching the upper limit), then drop several fields and create new ones, but the addition failed.

Create a table with 1600 fields (reaching the upper limit), then drop several fields and create new ones, but the addition failed.

test=# alter table t1 add column co1599 int;
ALTER TABLE
test=# alter table t1 add column co1600 int;
ALTER TABLE

test=# alter table t1 add column co1601 int;
psql: ERROR:  table can have at most 1600 columns

then, I drop column co1600 and add it again, failed:

test=# alter table t1 drop column co1600;
ALTER TABLE
test=# alter table t1 add column co1600 int;
psql: ERROR:  table can have at most 1600 columns

then, I drop column co1600 again:

test=# alter table t1 drop column co1600;
psql: ERROR: column "co1600" of relation "t1" dose not exist