Function createSpanIterator

tempodb/encoding/vparquet4/block_traceql.go:1907–2236

createSpanIterator iterates through all span-level columns, groups them into rows representing one span each. Spans are returned that match any of the given conditions.

(makeIter, makeNilIter makeIterFn, innerIterators []parquetquery.Iterator, conditions []traceql.Condition, allConditions bool, dedicatedColumns backend.DedicatedColumns, selectAll bool,
	sampler traceql.Sampler,
)

// createSpanIterator iterates through all span-level columns, groups them into rows representing
// one span each.  Spans are returned that match any of the given conditions.
func createSpanIterator(makeIter, makeNilIter makeIterFn, innerIterators []parquetquery.Iterator, conditions []traceql.Condition, allConditions bool, dedicatedColumns backend.DedicatedColumns, selectAll bool,
	sampler traceql.Sampler,
) (parquetquery.Iterator, error) {
	var (
		columnSelectAs          = map[string]string{}
		columnPredicates        = map[string][]parquetquery.Predicate{}
		iters                   []parquetquery.Iterator
		genericConditions       []traceql.Condition
		columnMapping           = dedicatedColumnsToColumnMapping(dedicatedColumns, backend.DedicatedColumnScopeSpan)
		nestedSetLeftExplicit   = false
		nestedSetRightExplicit  = false
		nestedSetParentExplicit = false
	)

	// todo: improve these methods. if addPredicate gets a nil predicate shouldn't it just wipe out the existing predicates instead of appending?
	// nil predicate matches everything. what's the point of also evaluating a "real" predicate?
	addPredicate := func(columnPath string, p parquetquery.Predicate) {
		columnPredicates[columnPath] = append(columnPredicates[columnPath], p)
	}

	addNilPredicateIfNotAlready := func(path string) {
		preds := columnPredicates[path]
		foundOpNone := false

		// check to see if there is a nil predicate and only add if it doesn't exist
		for _, pred := range preds {
			if pred == nil {
				foundOpNone = true
				break
			}
		}

		if !foundOpNone {
			addPredicate(path, nil)
			columnSelectAs[path] = path
		}
	}

	specialCase := func(cond traceql.Condition, columnPath string) (handled bool) {
		// Operands that need special handling.
		switch cond.Op {
		case traceql.OpNone:
			addPredicate(columnPath, nil) // No filtering
			columnSelectAs[columnPath] = cond.Attribute.Name
			return true
		case traceql.OpExists:
			addPredicate(columnPath, &parquetquery.SkipNilsPredicate{})
			columnSelectAs[columnPath] = cond.Attribute.Name
			return true
		case traceql.OpNotExists:
			iters = append(iters, makeIter(columnPath, parquetquery.NewNilValuePredicate(), cond.Attribute.Name))
			return true
		default:
			return false
		}
	}

	for _, cond := range conditions {