[ARROW-17431] [Java] MapBinder to bind Arrow Map type to DB column

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 10.0.0
• Fix Version/s: 10.0.0
• Component/s: Java
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/20370
• Assignee: Igor Suhorukov
• Reporter: Igor Suhorukov
• Created: 16/Aug/22 11:24
• Updated: 11/Jan/23 11:50
• Resolved: 24/Aug/22 11:44

Description

Typical real life Arrow datasets contain Map type vectors of string key->string value. Looks logically implement default JDBC parameter binders for such vector type or implement some kind on binder code extensibility of core framework via MetaINF/ServiceLocator

Current implementation just throws UnsupportedOperationException]

 

  @Override
        
        
            public ColumnBinder visit(ArrowType.Map type) {
        
        
              throw new UnsupportedOperationException("No column binder implemented for type " + type);
        
        
            } 

 
My current implementation patch ColumnBinderArrowTypeVisitor in classpath to return MapBinder

    @Override
    public ColumnBinder visit(ArrowType.Map type) {
        return  new MapBinder((MapVector) vector);
    }

and following code works for me with H2 database and in java stored PostgreSQL function in PL/Java to bind Map(string,string) parameter to JDBC:

package org.apache.arrow.adapter.jdbc.binder;

import org.apache.arrow.vector.complex.MapVector;
import org.apache.arrow.vector.complex.impl.UnionMapReader;
import org.apache.arrow.vector.util.JsonStringHashMap;

import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Types;
import java.util.LinkedHashMap;

public class MapBinder extends BaseColumnBinder<MapVector> {

    private UnionMapReader reader;

    public MapBinder(MapVector vector) {
        this(vector, Types.VARCHAR);
    }

    public MapBinder(MapVector vector, int jdbcType) {
        super(vector, jdbcType);
        reader = vector.getReader();
    }

    @Override
    public void bind(PreparedStatement statement, int parameterIndex, int rowIndex) throws SQLException {
        reader.setPosition(rowIndex);
        LinkedHashMap<String, String> tags = new JsonStringHashMap<>();
        while (reader.next()){
            tags.put(reader.key().readText().toString(), reader.value().readText().toString());
        }
        statement.setString(parameterIndex, tags.toString());
    }
}

 

Issue Links

• is a clone of: ARROW-17430 [Java] ListBinder to bind Arrow List type to DB column
• links to: GitHub Pull Request #13941