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Date: Wed, 7 Feb 2007 21:21:05 -0800 (PST)
From: "Saurabh Vyas (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Commented: (DERBY-2287) JDBC meta data for precision and
 size is inconsistent and does not match JDBC specifications.
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    [ https://issues.apache.org/jira/browse/DERBY-2287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12471191 ] 

Saurabh Vyas commented on DERBY-2287:
-------------------------------------

Thanks Dag & Dan for your inputs. The inconsistency lies in the different values used in metadata.properties & value returned getDigitPrecision() method. 
With the info provided by Dag,  is my understanding correct ?

> NUMERIC and DECIMAL have decimal precision. 
implies that INT_PRECISION, SMALLINT_PRECISION, LONGINT_PRECISION etc is the correct value to be used for the precision of exact NUMERIC types.

> This makes me believe the correct precision for REAL, FLOAT and DOUBLE
>  should be in terms of binary digits.
then REAL_PRECISION, DOUBLE_PRECISION etc value to be used for precision of REAL, FLOAT & DOUBLE. Thus rather than calling getDigitPrecision() for approximate data types, we should call getPrecision() method only & modify this method to add cases for approximate data types also

Comments / Suggestions ?

But again, any input on how to handle precision for  DATE & JAVACLASSNAME ?

> JDBC meta data for precision and size is inconsistent and does not match JDBC specifications.
> ---------------------------------------------------------------------------------------------
>
>                 Key: DERBY-2287
>                 URL: https://issues.apache.org/jira/browse/DERBY-2287
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC, Network Client
>    Affects Versions: 10.0.2.0, 10.0.2.1, 10.1.1.0, 10.1.2.1, 10.1.3.1, 10.2.1.6, 10.2.2.0
>            Reporter: Daniel John Debrunner
>            Priority: Minor
>
> JDBC 4.0 has clarified the definitions of precision in the java doc for various methods that return precision or size. The concept of precision and size seems to be the same, just having different method or column names in various situations.
> Derby does not follow the JDBC 4 specifications consistently, for example -1 is sometimes used to indicate not applicable, where JBDC 4 says NULL or 0. The precision of datetime columns is defined to be non-zero but in some situations Derby returns 0.
> jdbcapi.DatabaseMetaDataTest can show some of these issues, the test of getColumns() should compare the information in the COLUMN_SIZE column to the ResultSetMetaData getPrecision() method for the same column. The comparisions are not made currently because the number of mismatches is high. [this code is not yet committed].
> Existing application impact as Derby applications may have been relying on the old incorrect & inconsistent behaviour.

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