Function NewLeftJoinIterator

pkg/parquetquery/iters.go:1242–1286

(definitionLevel int, required, optional []Iterator, pred GroupPredicate, opts ...LeftJoinIteratorOption)

var _ Iterator = (*LeftJoinIterator)(nil)

func NewLeftJoinIterator(definitionLevel int, required, optional []Iterator, pred GroupPredicate, opts ...LeftJoinIteratorOption) (*LeftJoinIterator, error) {
	j := &LeftJoinIterator{
		required: required,
		optional: optional,
		pool:     DefaultPool,
	}

	// Fill in config slices for the explicitly given iterators first.
	for range j.required {
		j.defLevelsRequired = append(j.defLevelsRequired, definitionLevel)
		j.paramsRequired = append(j.paramsRequired, nil)
	}
	for range j.optional {
		j.defLevelsOptional = append(j.defLevelsOptional, definitionLevel)
		j.paramsOptional = append(j.paramsOptional, nil)
	}

	for _, opt := range opts {
		opt.applyToLeftJoinIterator(j)
	}

	// Any join requires at least one required iterator. If there are no required iterators,
	// use a UnionIterator instead.
	if len(j.required) == 0 {
		return nil, fmt.Errorf("left join iterator requires at least one required iterator")
	}

	if j.collector == nil {
		j.collector = newOldStyleCollector(j.pool, pred)
	}

	j.peeksRequired = make([]*IteratorResult, len(j.required))
	j.peeksOptional = make([]*IteratorResult, len(j.optional))
	j.collectedThroughRequired = make([]RowNumber, len(j.required))
	j.collectedThroughOptional = make([]RowNumber, len(j.optional))

	for i := range j.collectedThroughRequired {
		j.collectedThroughRequired[i] = EmptyRowNumber()
	}
	for i := range j.collectedThroughOptional {
		j.collectedThroughOptional[i] = EmptyRowNumber()
	}

	return j, nil
}

func (j *LeftJoinIterator) String() string {
	srequired := "required: "