How to Determine the Size of a Java ResultSet?

Obtaining the Size of a Java ResultSet

Calculating the size of a java.sql.ResultSet may seem like a simple task, but it lacks direct methods like size() or length().

Solution 1: SELECT COUNT(*) Query

One approach is to execute a separate SELECT COUNT(*) FROM ... query to determine the number of rows in the result set. This can be efficient if the result set is large, as it avoids the need to iterate through the entire dataset.

Solution 2: rs.last() Method

Alternatively, you can use the rs.last() method, which moves the cursor to the last row of the result set. The row index obtained using rs.getRow() can then be used as the size of the result set. This method is more efficient for smaller result sets, as it avoids the overhead of executing an additional query.

Example

ResultSet rs = ...;
int size = 0;

if (rs != null) {
  rs.last(); // Move cursor to the last row
  size = rs.getRow(); // Get the row index, which represents the size of the result set
}

Note

Both approaches provide ways to determine the size of a result set without having to iterate through the entire data. The choice between the two methods depends on the size and performance characteristics of the result set.

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