Golang IteratorOptions.MergeSorted方法代码示例

// createVarRefIterator creates an iterator for a variable reference.
func (e *Engine) createVarRefIterator(opt influxql.IteratorOptions) ([]influxql.Iterator, error) {
	ref, _ := opt.Expr.(*influxql.VarRef)

	var itrs []influxql.Iterator
	if err := func() error {
		mms := tsdb.Measurements(e.index.MeasurementsByName(influxql.Sources(opt.Sources).Names()))

		for _, mm := range mms {
			// Determine tagsets for this measurement based on dimensions and filters.
			tagSets, err := mm.TagSets(opt.Dimensions, opt.Condition)
			if err != nil {
				return err
			}

			// Calculate tag sets and apply SLIMIT/SOFFSET.
			tagSets = influxql.LimitTagSets(tagSets, opt.SLimit, opt.SOffset)

			for _, t := range tagSets {
				inputs, err := e.createTagSetIterators(ref, mm, t, opt)
				if err != nil {
					return err
				}

				if len(inputs) > 0 && (opt.Limit > 0 || opt.Offset > 0) {
					var itr influxql.Iterator
					if opt.MergeSorted() {
						itr = influxql.NewSortedMergeIterator(inputs, opt)
					} else {
						itr = influxql.NewMergeIterator(inputs, opt)
					}
					itrs = append(itrs, newLimitIterator(itr, opt))
				} else {
					itrs = append(itrs, inputs...)
				}
			}
		}
		return nil
	}(); err != nil {
		influxql.Iterators(itrs).Close()
		return nil, err
	}

	return itrs, nil
}

// CreateIterator returns a single combined iterator for the shards.
func (a Shards) CreateIterator(opt influxql.IteratorOptions) (influxql.Iterator, error) {
	if influxql.Sources(opt.Sources).HasSystemSource() {
		return a.createSystemIterator(opt)
	}

	// Create iterators for each shard.
	// Ensure that they are closed if an error occurs.
	itrs := make([]influxql.Iterator, 0, len(a))
	if err := func() error {
		for _, sh := range a {
			itr, err := sh.CreateIterator(opt)
			if err != nil {
				return err
			}
			itrs = append(itrs, itr)
		}
		return nil
	}(); err != nil {
		influxql.Iterators(itrs).Close()
		return nil, err
	}

	// Merge into a single iterator.
	if opt.MergeSorted() {
		return influxql.NewSortedMergeIterator(itrs, opt), nil
	}

	itr := influxql.NewMergeIterator(itrs, opt)
	if opt.Expr != nil {
		if expr, ok := opt.Expr.(*influxql.Call); ok && expr.Name == "count" {
			opt.Expr = &influxql.Call{
				Name: "sum",
				Args: expr.Args,
			}
		}
	}
	return influxql.NewCallIterator(itr, opt), nil
}

func TestIteratorOptions_MergeSorted(t *testing.T) {
	opt := influxql.IteratorOptions{}
	sorted := opt.MergeSorted()
	if !sorted {
		t.Error("expected no expression to be sorted, got unsorted")
	}

	opt.Expr = &influxql.VarRef{}
	sorted = opt.MergeSorted()
	if !sorted {
		t.Error("expected expression with varref to be sorted, got unsorted")
	}

	opt.Expr = &influxql.Call{}
	sorted = opt.MergeSorted()
	if sorted {
		t.Error("expected expression without varref to be unsorted, got sorted")
	}
}

// createVarRefIterator creates an iterator for a variable reference.
func (e *Engine) createVarRefIterator(opt influxql.IteratorOptions) ([]influxql.Iterator, error) {
	ref, _ := opt.Expr.(*influxql.VarRef)

	var itrs []influxql.Iterator
	if err := func() error {
		mms := tsdb.Measurements(e.index.MeasurementsByName(influxql.Sources(opt.Sources).Names()))

		// Retrieve the maximum number of fields (without time).
		conditionFields := make([]string, len(influxql.ExprNames(opt.Condition)))

		for _, mm := range mms {
			// Determine tagsets for this measurement based on dimensions and filters.
			tagSets, err := mm.TagSets(opt.Dimensions, opt.Condition)
			if err != nil {
				return err
			}

			// Calculate tag sets and apply SLIMIT/SOFFSET.
			tagSets = influxql.LimitTagSets(tagSets, opt.SLimit, opt.SOffset)

			for _, t := range tagSets {
				inputs := make([]influxql.Iterator, 0, len(t.SeriesKeys))
				for i, seriesKey := range t.SeriesKeys {
					fields := 0
					if t.Filters[i] != nil {
						// Retrieve non-time fields from this series filter and filter out tags.
						for _, f := range influxql.ExprNames(t.Filters[i]) {
							conditionFields[fields] = f
							fields++
						}
					}

					input, err := e.createVarRefSeriesIterator(ref, mm, seriesKey, t, t.Filters[i], conditionFields[:fields], opt)
					if err != nil {
						return err
					} else if input == nil {
						continue
					}
					inputs = append(inputs, input)
				}

				if len(inputs) > 0 && (opt.Limit > 0 || opt.Offset > 0) {
					var itr influxql.Iterator
					if opt.MergeSorted() {
						itr = influxql.NewSortedMergeIterator(inputs, opt)
					} else {
						itr = influxql.NewMergeIterator(inputs, opt)
					}
					itrs = append(itrs, newLimitIterator(itr, opt))
				} else {
					itrs = append(itrs, inputs...)
				}
			}
		}
		return nil
	}(); err != nil {
		influxql.Iterators(itrs).Close()
		return nil, err
	}

	return itrs, nil
}