On Mon, 13 Jan 2003, [iso-8859-1] Jimmy Mäkelä wrote: > I found that Postgres isn't behaving like I thought when using a unique index in > combination with NULL-values... > Is this a bug or specified in the SQL-standard? If its a bug, is it fixed in a > recent version? We are using 7.2.3
AFAIK this is standard. From the unique predicate (8.9), If there are no two rows in T such that the value of each column in one row is non-null and is equal to the value of the corresponding column in the other row according to Subclause 8.2, "comparison predicate", then the result of the unique predicate is true; otherwise, the result of the unique predicate is false. Unique constraints are defined in terms of the unique predicate. > And another completely unrelated question... I have got a table with a composite > index on A andBb and an index on A > which I query with something like this: > > SELECT * FROM "table" > WHERE (a = 1 OR a = 2 OR a = 3) AND b > 1232132 AND b < 123123123213123 > > Postgres then chooses to use the index for A three times, which is really slow > on my table... On my dev (7.4devel) box I see it using the composite index three times, but you haven't given explain output for the two queries or any statistics information so that doesn't say much. ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
