Golang SelectQuery.GetFromClause方法代碼示例

// Return the number of dropped ticks from filtering. if the series
// had more than one alias, returns the min of all dropped ticks
func (self *LevelDbDatastore) sendBatch(query *parser.SelectQuery, series *protocol.Series, yield func(series *protocol.Series) error) (int, error) {
	dropped := int(math.MaxInt32)

	for _, alias := range query.GetTableAliases(*series.Name) {
		_alias := alias
		newSeries := &protocol.Series{Name: &_alias, Points: series.Points, Fields: series.Fields}

		lengthBeforeFiltering := len(newSeries.Points)
		var filteredResult *protocol.Series
		var err error
		if query.GetFromClause().Type == parser.FromClauseInnerJoin {
			filteredResult = newSeries
		} else {
			filteredResult, err = Filter(query, newSeries)
			if err != nil {
				return 0, err
			}
		}
		_dropped := lengthBeforeFiltering - len(filteredResult.Points)
		if _dropped < dropped {
			dropped = _dropped
		}
		if err := yield(filteredResult); err != nil {
			return 0, err
		}
	}

	return dropped, nil
}

func Filter(query *parser.SelectQuery, series *protocol.Series) (*protocol.Series, error) {
	if query.GetWhereCondition() == nil {
		return series, nil
	}

	columns := map[string]struct{}{}
	if query.GetFromClause().Type == parser.FromClauseInnerJoin {
	outer:
		for t, cs := range query.GetResultColumns() {
			for _, c := range cs {
				// if this is a wildcard select, then drop all columns and
				// just use '*'
				if c == "*" {
					columns = make(map[string]struct{}, 1)
					columns[c] = struct{}{}
					break outer
				}
				columns[t.Name+"."+c] = struct{}{}
			}
		}
	} else {
		for _, cs := range query.GetResultColumns() {
			for _, c := range cs {
				columns[c] = struct{}{}
			}
		}
	}

	points := series.Points
	series.Points = nil
	for _, point := range points {
		ok, err := matches(query.GetWhereCondition(), series.Fields, point)

		if err != nil {
			return nil, err
		}

		if ok {
			fmt.Printf("columns: %v, fields: %v\n", columns, series.Fields)

			filterColumns(columns, series.Fields, point)
			series.Points = append(series.Points, point)
		}
	}

	if _, ok := columns["*"]; !ok {
		newFields := []string{}
		for _, f := range series.Fields {
			if _, ok := columns[f]; !ok {
				continue
			}

			newFields = append(newFields, f)
		}
		series.Fields = newFields
	}
	return series, nil
}

func getJoinYield(query *parser.SelectQuery, yield func(*protocol.Series) error) func(*protocol.Series) error {
	var lastPoint1 *protocol.Point
	var lastFields1 []string
	var lastPoint2 *protocol.Point
	var lastFields2 []string

	table1 := query.GetFromClause().Names[0].GetAlias()
	table2 := query.GetFromClause().Names[1].GetAlias()
	name := table1 + "_join_" + table2

	return mergeYield(table1, table2, false, query.Ascending, func(s *protocol.Series) error {
		fmt.Printf("join series: %d\n", len(s.Points))
		if *s.Name == table1 {
			lastPoint1 = s.Points[len(s.Points)-1]
			if lastFields1 == nil {
				for _, f := range s.Fields {
					lastFields1 = append(lastFields1, table1+"."+f)
				}
			}
		}

		if *s.Name == table2 {
			lastPoint2 = s.Points[len(s.Points)-1]
			if lastFields2 == nil {
				for _, f := range s.Fields {
					lastFields2 = append(lastFields2, table2+"."+f)
				}
			}
		}

		if lastPoint1 == nil || lastPoint2 == nil {
			return nil
		}

		newSeries := &protocol.Series{
			Name:   &name,
			Fields: append(lastFields1, lastFields2...),
			Points: []*protocol.Point{
				&protocol.Point{
					Values:    append(lastPoint1.Values, lastPoint2.Values...),
					Timestamp: lastPoint2.Timestamp,
				},
			},
		}

		lastPoint1 = nil
		lastPoint2 = nil

		filteredSeries, _ := Filter(query, newSeries)
		if len(filteredSeries.Points) > 0 {
			return yield(newSeries)
		}
		return nil
	})
}

// distribute query and possibly do the merge/join before yielding the points
func (self *QueryEngine) distributeQuery(user common.User, database string, query *parser.SelectQuery, yield func(*protocol.Series) error) (err error) {
	// see if this is a merge query
	fromClause := query.GetFromClause()
	if fromClause.Type == parser.FromClauseMerge {
		yield = getMergeYield(fromClause.Names[0].Name.Name, fromClause.Names[1].Name.Name, query.Ascending, yield)
	}

	if fromClause.Type == parser.FromClauseInnerJoin {
		yield = getJoinYield(query, yield)
	}

	return self.coordinator.DistributeQuery(user, database, query, yield)
}

// distribute query and possibly do the merge/join before yielding the points
func (self *QueryEngine) distributeQuery(query *parser.SelectQuery, yield func(*protocol.Series) error) error {
	// see if this is a merge query
	fromClause := query.GetFromClause()
	if fromClause.Type == parser.FromClauseMerge {
		yield = getMergeYield(fromClause.Names[0].Name.Name, fromClause.Names[1].Name.Name, query.Ascending, yield)
	}

	if fromClause.Type == parser.FromClauseInnerJoin {
		yield = getJoinYield(query, yield)
	}

	self.yield = yield
	return nil
}