Retrieve all Indexes for a given Table with JDBC

Question

I want to write a SpringBatch Tasklet, that automatically activates or de-activates all indexes for a given database table. The code needs to work independantly of the DBMS

Answer 1

You have to make a difference between primary keys (using DatabaseMetaData.getPrimaryKeys() to retrieve) and other indexes (via dbMetaData.getIndexInfo(null, null, tableName, true, false)).
In your loop use:

• rs.getString("INDEX_NAME") to extract index name
• rs.getBoolean("NON_UNIQUE") to extract unique information
• rs.getShort("TYPE") to extract index type
• rs.getInt("ORDINAL_POSITION") to extract ordinal position

Use ORDINAL_POSITION as key break (when current value is <= of previous one) to detect index change.
Read official DatabaseMetaData.getIndexInfo() doc

Answer 2

Below code is used to retrieve the INDEX_NAME From the DATABASE.

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

public class Main {
    public static void main(String[] args) throws Exception {
        Connection conn = getOracleConnection();  //Based on the database corresponding method should be called
        List<String> schemaList=new ArrayList<String>();
        List<String> catalogList=new ArrayList<String>();
        List<String> indexs=new ArrayList<String>();
        String dbIndexName=null;
        ResultSet rs=null;
        System.out.println("Got Connection.");
        try {
            DatabaseMetaData metaData = conn.getMetaData();

            ResultSet schemas = metaData.getSchemas();
            ResultSet catalog = metaData.getCatalogs();
            while (schemas.next()) {
                String tableSchema = schemas.getString(1);  
                schemaList.add(tableSchema);
            }
            while (catalog.next()) {
                String allCatalog = catalog.getString(1);  
                catalogList.add(allCatalog);
            }


            for(int i=0;i<schemaList.size();i++){
                try{
                    if(schemaList.get(i)!=null){
                        ResultSet indexValues = metaData.getIndexInfo(null, schemaList.get(i),tablename, true, false);

                        while (indexValues.next()) {

                            dbIndexName = indexValues.getString("INDEX_NAME");
                            if(dbIndexName!=null){
                                indexs.add(dbIndexName);
                            }
                        }
                        System.out.println("CORRESPONDING TABLE SCHEMA IS : "+schemaList.get(i));
                        System.out.println("INDEX_NAMES IS ::: "+indexs);
                    }

                }catch(Exception e){
            }

        }
    } finally {
        if (conn != null) {
            conn.close();
        }
    }
}

public static Connection getOracleConnection() throws Exception {
    String driver = "oracle.jdbc.OracleDriver";
    String url = "jdbc:oracle:thin:@localhost:1521:oracledb";
    String username = "oop";
    String password = "oop";

    Class.forName(driver); // load Oracle driver
    Connection conn = DriverManager.getConnection(url, username, password);
    return conn;
}

private static Connection getDB2Connection() throws Exception {
    Class.forName("org.hsqldb.jdbcDriver");
    System.out.println("Driver Loaded.");
    String url = "jdbc:hsqldb:data/tutorial";
    return DriverManager.getConnection(url, "sa", "");
}

public static Connection getMySqlConnection() throws Exception {
    String driver = "org.gjt.mm.mysql.Driver";
    String url = "jdbc:mysql://localhost/demo2s";
    String username = "oost";
    String password = "oost";

    Class.forName(driver);
    Connection conn = DriverManager.getConnection(url, username, password);
    return conn;
}

}

Answer 3

I had a similar problem and the cause in my case was, the case-sensitivity. I had to write the whole tablename in lower case letters (like it appeared in the result set of the SQL "SELECT tablename,indexname,indexdef FROM pg_indexes".

I also changed the second last parameter ("unique" parameter) to false to get all indexes (otherwise I just got the primary key).

Hope this helps.

Answer 4

The other way of getting all indexes is using the information_schema statistics table:

public void GetIndexesOfThisTable(final String tableName) {
    try {
        PreparedStatement ps = conn.prepareStatement("SELECT DISTINCT INDEX_NAME FROM information_schema.statistics WHERE table_name = ?");
        ps.setString(1, tableName);
        ResultSet rs = ps.executeQuery();

        while(rs.next()){
            System.out.println(rs.getString(1));
        }
        rs.close();
        ps.close();//important to close to prevent resource leaks
    }
    catch (Exception ex) {System.out.println(ex.getMessage());}        
}