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From "Saurabh Vyas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2287) JDBC meta data for precision and size is inconsistent and does not match JDBC specifications.
Date Wed, 07 Feb 2007 15:37:05 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12470999

Saurabh Vyas commented on DERBY-2287:

After some investigation I found that getDigitPrecision() method  in DataTypeUtilities.java
returns precision values which is inconsistent with that returned from metadata.properties.
I tried following modification :

public static int getDigitPrecision(DataTypeDescriptor dtd) {
                int typeId = dtd.getTypeId().getJDBCTypeId();
                switch ( typeId )
                      case Types.FLOAT:
                      case Types.DOUBLE:
                              //return TypeId.DOUBLE_PRECISION_IN_DIGITS;
                              return TypeId.DOUBLE_PRECISION;
                       case Types.REAL:
                             //return TypeId.REAL_PRECISION_IN_DIGITS;
                             return TypeId.REAL_PRECISION;
                      //Added case for Date & time data type
                      case Types.DATE:
                      case Types.TIME:
                      case Types.TIMESTAMP:
                            return dtd.getMaximumWidth();
                      default: return getPrecision(dtd);

Then I tried the assert in crossCheckGetColumnRowAndResultSetMetaData() method of DatabaseMetaDataTest.java
which  was failing for DATE , REAL and other data types :
          assertEquals("COLUMN_SIZE",  rsmdt.getPrecision(col), rs.getInt("COLUMN_SIZE"));

After above change, DATE & REAL data type are consistent in precision values and assert
but I got assert for JAVACLASSNAME type. This I was not able to root cause.
Now I have two questions :
 - Is my approach for DATE & REAL data type correct
 - What is JAVACLASSNAME type & how to handle this.

> 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:,,,,,,
>            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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