If we can translate to an equivalent expression, then I think it is better
to do that. Iceberg expressions don't support SQL semantics and it would be
a big project to convert them. Afterward, we would just have more
complicated expressions that are harder to maintain because SQL semantics
are
No, you can translate these expressions, but you have to evaluate the
entire expression. For example:
"col1 = 'x' and col2 in (1,2)" becomes col1 = 'x' and col2 in (1,2)
"not(col1 = 'x' and col2 in (1,2))" becomes (col1 != 'x' or col2 not in
(1,2)) and col1 is not null and col2 is not null
Are you saying that we can't fix this by rewriting expressions to translate
from SQL to more natural semantics?
On Fri, Sep 18, 2020 at 3:28 PM Owen O'Malley
wrote:
> In the SQL world, the second point isn't right. It is still the case that
> not(equal("col", "x")) is notEqual("col", "x").
In the SQL world, the second point isn't right. It is still the case that
not(equal("col", "x")) is notEqual("col", "x"). Boolean logic (well, three
valued logic) in SQL is just strange relative to programming languages:
- null *=* "x" -> null
- null *is distinct from* "x" -> true
-
It would be nice to avoid the problem by changing the semantics of
Iceberg’s notNull, but I don’t think that’s a good idea for 2 main reasons.
First, I think that API users creating expressions directly expect the
current behavior. It would be surprising to a user if a notEqual expression
didn’t
I think that we should follow the SQL semantics to prevent surprises when
SQL engines integrate with Iceberg.
.. Owen
On Thu, Sep 17, 2020 at 9:08 PM Shardul Mahadik
wrote:
> Hi all,
>
> I noticed that Iceberg's predicates are not compatible with SQL predicates
> when it comes to handling NULL
Hi all,
I noticed that Iceberg's predicates are not compatible with SQL predicates
when it comes to handling NULL values. In SQL, if any of the operands of a
scalar comparison predicate is NULL, then the resultant truth value of the
predicate is UNKNOWN. e.g. `SELECT NULL != 1` will return a NULL
