Method Query

exec/sqldriver.go:228–280

Query executes a query that may return rows, such as a SELECT

(args []driver.Value)

// Query executes a query that may return rows, such as a SELECT
func (m *qlbStmt) Query(args []driver.Value) (driver.Rows, error) {
	var err error
	if len(args) > 0 {
		m.query, err = queryArgsConvert(m.query, args)
		if err != nil {
			return nil, err
		}
	}
	u.Debugf("query: %v", m.query)

	// Create a Job, which is Dag of Tasks that Run()
	ctx := plan.NewContext(m.query)
	ctx.Schema = m.conn.schema
	job, err := BuildSqlJob(ctx)
	if err != nil {
		u.Warnf("return error? %v", err)
		return nil, err
	}
	m.job = job

	// The only type of stmt that makes sense for Query is SELECT
	//  and we need list of columns that requires casing
	sqlSelect, ok := job.Ctx.Stmt.(*rel.SqlSelect)
	if !ok {
		u.Warnf("ctx? %v", job.Ctx)
		return nil, fmt.Errorf("We could not recognize that as a select query: %T", job.Ctx.Stmt)
	}

	// Prepare a result writer, we manually append this task to end
	// of job?
	resultWriter := NewResultRows(ctx, sqlSelect.Columns.AliasedFieldNames())

	job.RootTask.Add(resultWriter)

	job.Setup()

	// TODO:   this can't run in parallel-buffered mode?
	// how to open in go-routine and still be able to send error to rows?
	go func() {
		//u.Debugf("Start Job.Run")
		err = job.Run()
		//u.Debugf("After job.Run()")
		if err != nil {
			u.Errorf("error on Query.Run(): %v", err)
			//resultWriter.ErrChan() <- err
			//job.Close()
		}
		job.Close()
		//u.Debugf("exiting Background Query")
	}()

	return resultWriter, nil
}

// driver.ColumnConverter Interface implementation.
//