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From "Lance J. Andersen" <Lance.Ander...@Sun.COM>
Subject Re: [jira] Commented: (DERBY-142) ResultSetMetaData.isReadOnly() also returns wrong results
Date Wed, 12 Oct 2005 19:04:19 GMT
Ah, quick is not always possible in the land as standards as you are 
probably aware.

I will let you know how it goes.


Satheesh Bandaram wrote:

> Great... Thanks for discussing this at the EG this week. Please let us 
> know of any outcome, if possible. I am willing to address the problem 
> either way, once we reach some conclusion.
> Here are some of the points to consider:
>    1. ODBC spec is unambiguous... It says
>       ResultSetMetaData.isReadOnly() should return information about
>       the result column, not the base column. JDBC doesn't need to
>       follow ODBC here, but something to keep in mind.
>    2. Thomas Fischer seems to indicate many JDBC drivers implement
>       isReadOnly to refer to base column, not the result column. But
>       my testing with DB2 seems to indicate that isReadOnly() returns
>       information about the result column NOT the base column. I
>       haven't tested with other database drivers.
>    3. Both you and Dan pointed to the fact that this method was there
>       in JDBC 1.0, which predates updatable resultsets.
>    4. It would make more sense to make ResultSetMetaData.isReadOnly()
>       to reflect ResultSet itself, rather than the base table.
>       DatabaseMetaData might be more appropriate for checking for
>       read/writeOnly info for base columns.
> Again, I am OK with implementing a consensus either way. Hope we can 
> reach one, quickly. :-)
> Satheesh
> Lance J. Andersen wrote:
>> As i mentioned earlier, i will be addressing the lack of clarity in 
>> the JDBC 4.0 spec, for the public draft (EDR2 just went to the JCP 
>> and should be posted shortly)/
>> These metadata methods were added during the initial JDBC 1.0.2 
>> release which was prior to updatable resultsets within jdbc.   
>> I am going to be discussing this in my weekly EG call this week.
>> -lance
>> Jean T. Anderson (JIRA) wrote:
>>>    [ http://issues.apache.org/jira/browse/DERBY-142?page=comments#action_12331849
>>>Jean T. Anderson commented on DERBY-142:
>>>So Torque uses Village ( http://www.softwareforge.de/releases/village/ ) to insert/modify
datasets. Here are a few more details about what Village does under the hood after a (very
quick) look at it. (Torque lurkers should feel free to correct these details.)
>>>Village obtains the schema for a given table with this query:
>>>     String sql = "SELECT " + columnsAttribute + " FROM " + tableName + " WHERE
1 = -1";
>>>This query will work in any database, so this much makes sense. And it also makes
sense to me that they wouldn't include a "FOR  UPDATE" clause on it. At this point, they're
just building internal information about the schema.
>>>Information for each column is then obtained with the ResultSetMetaData methods,
including whether or not the column is writeable with that isReadOnly method call. The Village
method that inserts a new row only does so if the columns are writeable. Hence the current
>>>I'm looking at the jdbc docs at http://java.sun.com/j2se/1.4.2/docs/api/java/sql/ResultSetMetaData.html
and I'm not seeing clearly whether these metadata calls are intended to just describe columns
in the result set or columns in the underlying table:
>>>   - isReadOnly: "Indicates whether the designated column is definitely not writable."
>>>   - isWritable: "Indicates whether it is possible for a write on the designated
column to succeed.".
>>>What is the "designated column"? Just the result set? Or could it also refer to
the underlying table?
>>>I'm looking at the "JDBC API Tutorial and Reference, Third Edition", and section
27.1.19 on "Queries That Produce Updateable Result Sets" suggests to me a strong association
with the permissions on the underlying table. --I'm left wondering what it might mean to update
a result set outside the context of an underlying table.
>>>>ResultSetMetaData.isReadOnly() also returns wrong results
>>>>         Key: DERBY-142
>>>>         URL: http://issues.apache.org/jira/browse/DERBY-142
>>>>     Project: Derby
>>>>        Type: Sub-task
>>>>  Components: JDBC
>>>>    Versions:
>>>> Environment: Using DB2 universal driver with standalone derby server
>>>>    Reporter: Thomas Fischer
>>>> Attachments: DerbyTest.java, DerbyTest142.java
>>>>ResultSetMetaData.isReadOnly() always returns true, even when writing to the
table is possible.  
>>>>The JDBC 2.0 spec says: "ResultSetMetaData.isReadOnly() : Indicates whether
the designated column is definitely not writable.", so the method should return false for
a table.
>>>>I will attach a testcase for this behaviour.

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