Tom Duffey wrote: > Here is a smaller test case that does not involve Java. I guess this probably > is just due to floating > point error when the initial value is inserted that is too large for the > field but it's still a > surprise. > > Create a test table, insert a couple values and view the results: > > CREATE TABLE test ( > id INTEGER PRIMARY KEY, > value REAL NOT NULL > ); > > INSERT INTO test (id, value) VALUES (1, 10.3884573), (2, 10.3885); > SELECT * FROM test; > > id | value > ----+--------- > 1 | 10.3885 > 2 | 10.3885 > (2 rows)
SET extra_float_digits=3; SELECT * FROM test; id | value ----+------------ 1 | 10.3884573 2 | 10.3885002 (2 rows) PostgreSQL by default omits the last three digits to avoid differences on different architectures (I think). When you convert to double precision, you'll see these digits. > At this point you would think you have two equal values. Now change the type: > > ALTER TABLE test ALTER COLUMN value TYPE DOUBLE PRECISION; > SELECT * FROM test; > > id | value > ----+------------------ > 1 | 10.3884572982788 > 2 | 10.388500213623 > (2 rows) Yours, Laurenz Albe -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
