6.9.1.4.6.1 Query Options Controlled by Explicit Arguments

Some query options are controlled by explicit arguments to methods in the Java API.

• The executeQuery method of PgqlStatement has explicit arguments for timeout in seconds, degree of parallelism, optimizer dynamic sampling, and maximum number of results.

• The translateQuery method has explicit arguments for degree of parallelism, optimizer dynamic sampling, and maximum number of results. PgqlPreparedStatement also provides those same additional arguments for executeQuery and translateQuery.

Example 6-17 PgqlExample10.java

PgqlExample10.java shows PGQL query execution with additional options controlled by explicit arguments.

import java.sql.Connection;

import oracle.pg.rdbms.pgql.PgqlConnection;
import oracle.pg.rdbms.pgql.PgqlResultSet;
import oracle.pg.rdbms.pgql.PgqlStatement;

import oracle.ucp.jdbc.PoolDataSourceFactory;
import oracle.ucp.jdbc.PoolDataSource;

/**
 * This example shows how to execute a PGQL query with various options.
 */
public class PgqlExample10
{

  public static void main(String[] args) throws Exception
  {
    int idx=0;
    String host               = args[idx++]; 
    String port               = args[idx++]; 
    String sid                = args[idx++]; 
    String user               = args[idx++]; 
    String password           = args[idx++];
    String graph              = args[idx++];

    Connection conn = null;
    PgqlStatement ps = null;
    PgqlResultSet rs = null;

    try {

      //Get a jdbc connection
      PoolDataSource  pds = PoolDataSourceFactory.getPoolDataSource();
      pds.setConnectionFactoryClassName("oracle.jdbc.pool.OracleDataSource");
      pds.setURL("jdbc:oracle:thin:@"+host+":"+port +":"+sid);
      pds.setUser(user);
      pds.setPassword(password);     
      conn = pds.getConnection();

      // Get a PGQL connection
      PgqlConnection pgqlConn = PgqlConnection.getConnection(conn);
      pgqlConn.setGraph(graph);

      // Create a PgqlStatement
      ps = pgqlConn.createStatement();

      // Execute query to get a ResultSet object
      String pgql = 
        "SELECT v1.\"fname\" AS fname1, v2.\"fname\" AS fname2 "+
        "FROM MATCH (v1)-[:\"friendOf\"]->(v2)";
      rs = ps.executeQuery(pgql /* query string */, 
                           100  /* timeout (sec): 0 is default and implies no timeout */,
                           2    /* parallel: 1 is default */,
                           6    /* dynamic sampling: 2 is default */,
                           50   /* max results: -1 is default and implies no limit */,
                           ""   /* options */);

      // Print query results
      rs.print();
    }
    finally {
      // close the result set
      if (rs != null) {
        rs.close();
      }
      // close the statement
      if (ps != null) {
        ps.close();
      }
      // close the connection
      if (conn != null) {
        conn.close();
      }
    }
  }
}

PgqlExample10.java gives the following output for test_graph (which can be loaded using GraphLoaderExample.java code).

+-----------------+
| FNAME1 | FNAME2 |
+-----------------+
| Ray    | Susan  |
| John   | Susan  |
| Bill   | John   |
| Susan  | John   |
| John   | Bill   |
+-----------------+