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https://issues.apache.org/jira/browse/HIVE-6167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13865845#comment-13865845
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Jason Dere commented on HIVE-6167:
----------------------------------
[~xuefuz] brought up this point:
{quote}
Reading the document, I found one thing that seems to be debatable:
1. Creating a function w/o database name means "in the current database of the
session".
2. Creating a temp function 2/o database name means global in the system as
built-in functions.
I understand the consideration of backward compatibility, but the discrepancy
can confuse the user a great deal. Why cannot we change #1 in the same way for
temp functions?
1'. Creating a function w/o database name means global in the system as
built-in functions.
{quote}
It would make sense for there to be some consistency with the default database
name for temporary/permanent functions. I've also been playing with qualifying
built-in functions with schema names and I don't really like the effect on
"describe functions":
{noformat}
hive> show functions;
OK
default.myfunc
mydb.myfunc
sys.!
sys.!=
sys.%
sys.&
sys.*
sys.+
sys.-
sys./
sys.<
sys.<=
sys.<=>
sys.<>
sys.=
sys.==
sys.>
sys.>=
sys.^
sys.abs
sys.acos
sys.and
sys.array
sys.array_contains
sys.ascii
...
{noformat}
Many of these functions will not work if they are called as they are labelled,
such as any of the operators (sys.+ wouldn't work), or any keywords that are
implemented as functions. So I'm wondering if the built-in functions can be in
the registry as non-qualified function names. However, I think that if we do
have permanent functions, that they should be qualified. But we also want
consistency in default db name between temp and permanent functions.
So how about this behavior:
- Built-in functions are not qualified
- User-defined functions (temp/permanent) that are created without a database
name will be created using the database name "default".
- Function resolution of non-qualified functions will be in the following order:
1. Lookup using non-qualified name, which will catch built-ins
2. Lookup by qualifying function name with "default". This will catch
non-qualified user-defined functions
3. Lookup by qualifying function name with user's current database.
I suppose a future enhancement could be to allow users to specify a custom set
of db names when resolving function names, but I think the above would be a
suitable default. Does this approach make sense?
> Allow user-defined functions to be qualified with database name
> ---------------------------------------------------------------
>
> Key: HIVE-6167
> URL: https://issues.apache.org/jira/browse/HIVE-6167
> Project: Hive
> Issue Type: Sub-task
> Components: UDF
> Reporter: Jason Dere
> Assignee: Jason Dere
>
> Function names in Hive are currently unqualified and there is a single
> namespace for all function names. This task would allow users to define
> temporary UDFs (and eventually permanent UDFs) with a database name, such as:
> CREATE TEMPORARY FUNCTION userdb.myfunc 'myudfclass';
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