[jira] [Created] (BEAM-10946) JdbcIO should make the 'COMMENT' metadata available as Description

["Yann Landrin-Schweitzer (Jira)" <ji...@apache.org>]

Yann Landrin-Schweitzer created BEAM-10946:
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             Summary: JdbcIO should make the 'COMMENT' metadata available as Description
                 Key: BEAM-10946
                 URL: https://issues.apache.org/jira/browse/BEAM-10946
             Project: Beam
          Issue Type: Improvement
          Components: io-java-jdbc
    Affects Versions: 2.23.0
            Reporter: Yann Landrin-Schweitzer


Currently, creating a PCollection<Row> using JdbcIO.readRows() does not make available:

 - a column's COMMENT or REMARKS metadata as the corresponding Beam field Description

 - a table COMMENT or REMARKS metadata as an appropriately named Beam schema Option

 

Making this metadata available would strongly benefit IDEs providing in-line help to create Beam pipelines, as well as semi-automated data labelling tools using metadata to infer data properties.

 

Sketch of the proposed changes in JdbcIO: 
{code:java}
@FunctionalInterface
interface BeamFieldConverter extends Serializable {
    Schema.Field create(int index, ResultSetMetaData md, DatabaseMetaData dmd) throws SQLException;
}
private static String getComment(int index, ResultSetMetaData md, DatabaseMetaData dmd) throws SQLException {
    String comment = null;
    if(dmd instanceof DatabaseMetaDataUsingInfoSchema) {
        ResultSet rs = dmd.getColumns(md.getCatalogName(index), md.getSchemaName(index), md.getTableName(index), md.getColumnName(index));
        if(rs.next()
           && md.getTableName(index).equals(rs.getString("TABLE_NAME"))
           && md.getColumnName(index).equals(rs.getString("COLUMN_NAME"))
        ) {
            comment = rs.getString("REMARKS");
        }
    }
    return comment;
}
{code}
 



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