[jira] Updated: (DBUTILS-37) BeanListHandler#handle(ResultSet) is not optimal

["Dennis Lundberg (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/DBUTILS-37?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Dennis Lundberg updated DBUTILS-37:
-----------------------------------

    Description: 
I use the BeanListHandler for huge ResultSets (about 1000000 rows), and I searched through the code to see if I could gain little time.

It appeared to me that the following code - in BeanProcessor.class - was executed too many times:

{code}
        PropertyDescriptor[] props = this.propertyDescriptors(type);
        ResultSetMetaData rsmd = rs.getMetaData();
        int[] columnToProperty = this.mapColumnsToProperties(rsmd, props);
{code}

for the following reason.
Since BeanListHandler extends GenericListHandler, the method #handle(ResultSet) calls #handleRow(ResultSet) for each row in the ResultSet, 
which in the case of a BeanListHandler, calls RowProcessor#toBean(ResultSet, Class),
which itself calls BeanProcessor#toBean(ResultSet, Class).

A very simple way to make the BeanListHandler#handle(ResultSet) method faster is to override the GenericListHandler#handle(ResultSet) method by this code:

{code}
    public Object handle(ResultSet rs) throws SQLException {
        return this.convert.toBeanList(rs, type);
    }
{code}

This way, the code I showed would be called only once, as it would not call BeanProcessor#toBean(ResultSet, Class) for each row but BeanProcessor#toBeanList(ResultSet, Class).


  was:
I use the BeanListHandler for huge ResultSets (about 1000000 rows), and I searched through the code to see if I could gain little time.

It appeared to me that the following code - in BeanProcessor.class - was executed too many times:

        PropertyDescriptor[] props = this.propertyDescriptors(type);
        ResultSetMetaData rsmd = rs.getMetaData();
        int[] columnToProperty = this.mapColumnsToProperties(rsmd, props);

for the following reason.
Since BeanListHandler extends GenericListHandler, the method #handle(ResultSet) calls #handleRow(ResultSet) for each row in the ResultSet, 
which in the case of a BeanListHandler, calls RowProcessor#toBean(ResultSet, Class),
which itself calls BeanProcessor#toBean(ResultSet, Class).

A very simple way to make the BeanListHandler#handle(ResultSet) method faster is to override the GenericListHandler#handle(ResultSet) method by this code:
    public Object handle(ResultSet rs) throws SQLException {
        return this.convert.toBeanList(rs, type);
    }
This way, the code I showed would be called only once, as it would not call BeanProcessor#toBean(ResultSet, Class) for each row but BeanProcessor#toBeanList(ResultSet, Class).



> BeanListHandler#handle(ResultSet) is not optimal
> ------------------------------------------------
>
>                 Key: DBUTILS-37
>                 URL: https://issues.apache.org/jira/browse/DBUTILS-37
>             Project: Commons DbUtils
>          Issue Type: Improvement
>            Reporter: Julien Aymé
>            Priority: Minor
>         Attachments: OptimalBeanListHandler.java, OptimalBeanListHandler.patch
>
>
> I use the BeanListHandler for huge ResultSets (about 1000000 rows), and I searched through the code to see if I could gain little time.
> It appeared to me that the following code - in BeanProcessor.class - was executed too many times:
> {code}
>         PropertyDescriptor[] props = this.propertyDescriptors(type);
>         ResultSetMetaData rsmd = rs.getMetaData();
>         int[] columnToProperty = this.mapColumnsToProperties(rsmd, props);
> {code}
> for the following reason.
> Since BeanListHandler extends GenericListHandler, the method #handle(ResultSet) calls #handleRow(ResultSet) for each row in the ResultSet, 
> which in the case of a BeanListHandler, calls RowProcessor#toBean(ResultSet, Class),
> which itself calls BeanProcessor#toBean(ResultSet, Class).
> A very simple way to make the BeanListHandler#handle(ResultSet) method faster is to override the GenericListHandler#handle(ResultSet) method by this code:
> {code}
>     public Object handle(ResultSet rs) throws SQLException {
>         return this.convert.toBeanList(rs, type);
>     }
> {code}
> This way, the code I showed would be called only once, as it would not call BeanProcessor#toBean(ResultSet, Class) for each row but BeanProcessor#toBeanList(ResultSet, Class).

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