jdbc: Support Statement.getMoreResults

[nicktorwald]

If there are multiple results or if the type or number of results returned by a Statement object are not known until run time, the Statement object should be executed with the method execute. The methods getMoreResults, getUpdateCount, and getResultSet can be used to retrieve all the results.

By default, each call to the method getMoreResults closes any previous ResultSet object returned by the method getResultSet. However, the method getMoreResults may take a parameter that specifies whether a ResultSet object returned by getResultSet should be closed. The Statement interface defines three constants that can be supplied to the method getMoreResults:

• CLOSE_CURRENT_RESULT — indicates that the current ResultSet object should be closed when the next ResultSet object is returned
• KEEP_CURRENT_RESULT — indicates that the current ResultSet object should not be closed when the next ResultSet object is returned
• CLOSE_ALL_RESULTS — indicates that any ResultSet objects that have been kept open should be closed when the next result is returned

If the current result is an update count and not a ResultSet object, any parameter passed to getMoreResults is ignored.

To determine whether a driver implements this feature, an application can call the
DatabaseMetaData method supportsMultipleOpenResults.

An example:

Statement stmt = conn.createStatement();
boolean retval = cstmt.execute(sql_queries);
ResultSet rs;
int count;
do {
    if (retval == false) {
        count = stmt.getUpdateCount();
        if (count == -1) {
            // no more results
           break;
        } else {
           // process update count
        }
    } else {
        rs = stmt.getResultSet();
        // process ResultSet
    }
    retval = stmt.getMoreResults();
while (true);

[Totktonada]

AFAIK, we cannot receive multiple result sets from tarantool sql now. Are we must support it according to JDBC?

[nicktorwald]

Yeah, we need to support getMoreResults() and getMoreResults(ResultSet.CLOSE_CURRENT_RESULT) even though a single result set. Both cases do the same.
Right now, we can just return false and close the current result set to follow the spec. We even can support KEEP_CURRENT_RESULT and CLOSE_ALL_RESULTS for the single result set.

I renamed the issue to be more precise.

[Totktonada]

Okay. Let's consider this issue as the task to appropriate support the API.