Merge pull request #15239 from colega/revert-14975-process-mempostings-delete-with-gomaxprocs-workers

Revert "Process `MemPostings.Delete()` with `GOMAXPROCS` workers"

tsdb/index/postings.go

@@ -26,7 +26,6 @@ import (
 	"sync"
 
 	"github.com/bboreham/go-loser"
-	"github.com/cespare/xxhash/v2"
 
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/storage"
@@ -293,17 +292,8 @@ func (p *MemPostings) EnsureOrder(numberOfConcurrentProcesses int) {
 func (p *MemPostings) Delete(deleted map[storage.SeriesRef]struct{}, affected map[labels.Label]struct{}) {
 	p.mtx.Lock()
 	defer p.mtx.Unlock()
-	if len(p.m) == 0 || len(deleted) == 0 {
-		return
-	}
 
-	// Deleting label names mutates p.m map, so it should be done from a single goroutine after nobody else is reading it.
+	process := func(l labels.Label) {
-	deleteLabelNames := make(chan string, len(p.m))
-
-	process, wait := processWithBoundedParallelismAndConsistentWorkers(
-		runtime.GOMAXPROCS(0),
-		func(l labels.Label) uint64 { return xxhash.Sum64String(l.Name) },
-		func(l labels.Label) {
 		orig := p.m[l.Name][l.Value]
 		repl := make([]storage.SeriesRef, 0, len(orig))
 		for _, id := range orig {
@@ -315,54 +305,17 @@ func (p *MemPostings) Delete(deleted map[storage.SeriesRef]struct{}, affected ma
 			p.m[l.Name][l.Value] = repl
 		} else {
 			delete(p.m[l.Name], l.Value)
-				if len(p.m[l.Name]) == 0 {
 			// Delete the key if we removed all values.
-					deleteLabelNames <- l.Name
+			if len(p.m[l.Name]) == 0 {
+				delete(p.m, l.Name)
+			}
 		}
 	}
-		},
-	)
 
 	for l := range affected {
 		process(l)
 	}
 	process(allPostingsKey)
-	wait()
-
-	// Close deleteLabelNames channel and delete the label names requested.
-	close(deleteLabelNames)
-	for name := range deleteLabelNames {
-		delete(p.m, name)
-	}
-}
-
-// processWithBoundedParallelismAndConsistentWorkers will call f() with bounded parallelism,
-// making sure that elements with same hash(T) will always be processed by the same worker.
-// Call process() to add more jobs to process, and once finished adding, call wait() to ensure that all jobs are processed.
-func processWithBoundedParallelismAndConsistentWorkers[T any](workers int, hash func(T) uint64, f func(T)) (process func(T), wait func()) {
-	wg := &sync.WaitGroup{}
-	jobs := make([]chan T, workers)
-	for i := 0; i < workers; i++ {
-		wg.Add(1)
-		jobs[i] = make(chan T, 128)
-		go func(jobs <-chan T) {
-			defer wg.Done()
-			for l := range jobs {
-				f(l)
-			}
-		}(jobs[i])
-	}
-
-	process = func(job T) {
-		jobs[hash(job)%uint64(workers)] <- job
-	}
-	wait = func() {
-		for i := range jobs {
-			close(jobs[i])
-		}
-		wg.Wait()
-	}
-	return process, wait
 }
 
 // Iter calls f for each postings list. It aborts if f returns an error and returns it.

tsdb/index/postings_test.go

@@ -973,7 +973,6 @@ func TestMemPostingsStats(t *testing.T) {
 }
 
 func TestMemPostings_Delete(t *testing.T) {
-	t.Run("some postings", func(t *testing.T) {
 	p := NewMemPostings()
 	p.Add(1, labels.FromStrings("lbl1", "a"))
 	p.Add(2, labels.FromStrings("lbl1", "b"))
@@ -1005,37 +1004,6 @@ func TestMemPostings_Delete(t *testing.T) {
 	expanded, err = ExpandPostings(deleted)
 	require.NoError(t, err)
 	require.Empty(t, expanded, "expected empty postings, got %v", expanded)
-	})
-
-	t.Run("all postings", func(t *testing.T) {
-		p := NewMemPostings()
-		p.Add(1, labels.FromStrings("lbl1", "a"))
-		p.Add(2, labels.FromStrings("lbl1", "b"))
-		p.Add(3, labels.FromStrings("lbl2", "a"))
-
-		deletedRefs := map[storage.SeriesRef]struct{}{1: {}, 2: {}, 3: {}}
-		affectedLabels := map[labels.Label]struct{}{
-			{Name: "lbl1", Value: "a"}: {},
-			{Name: "lbl1", Value: "b"}: {},
-			{Name: "lbl1", Value: "c"}: {},
-		}
-		p.Delete(deletedRefs, affectedLabels)
-		after := p.Get(allPostingsKey.Name, allPostingsKey.Value)
-		expanded, err := ExpandPostings(after)
-		require.NoError(t, err)
-		require.Empty(t, expanded)
-	})
-
-	t.Run("nothing on empty mempostings", func(t *testing.T) {
-		p := NewMemPostings()
-		deletedRefs := map[storage.SeriesRef]struct{}{}
-		affectedLabels := map[labels.Label]struct{}{}
-		p.Delete(deletedRefs, affectedLabels)
-		after := p.Get(allPostingsKey.Name, allPostingsKey.Value)
-		expanded, err := ExpandPostings(after)
-		require.NoError(t, err)
-		require.Empty(t, expanded)
-	})
 }
 
 // BenchmarkMemPostings_Delete is quite heavy, so consider running it with
@@ -1057,7 +1025,7 @@ func BenchmarkMemPostings_Delete(b *testing.B) {
 		return s
 	}
 
-	const total = 2e6
+	const total = 1e6
 	allSeries := [total]labels.Labels{}
 	nameValues := make([]string, 0, 100)
 	for i := 0; i < total; i++ {