chore: [k209] fix(blooms): ensure tokenizer cache is reset between series (#13371)

Backport 04bc3a4 from #13370

---

Fixes bug where ngrams were not added to blooms b/c they had been added previously to a potentially different series. This caused blooms to fail membership tests incorrectly.

Co-authored-by: Owen Diehl <[email protected]>

Author: grafanabot

pkg/storage/bloom/v1/bloom_tokenizer.go

@@ -97,11 +97,14 @@ func (bt *BloomTokenizer) newBloom() *Bloom {
 	}
 }
 
+// Populates a bloom filter(s) with the tokens from the given chunks.
+// Called once per series
 func (bt *BloomTokenizer) Populate(
 	blooms SizedIterator[*Bloom],
 	chks Iterator[ChunkRefWithIter],
 	ch chan *BloomCreation,
 ) {
+	clear(bt.cache) // MUST always clear the cache before starting a new series
 	var next bool
 
 	// All but the last bloom are considered full -- send back unaltered

pkg/storage/bloom/v1/bloom_tokenizer_test.go

@@ -288,6 +288,45 @@ func BenchmarkPopulateSeriesWithBloom(b *testing.B) {
 	}
 }
 
+func TestTokenizerClearsCacheBetweenPopulateCalls(t *testing.T) {
+	bt := NewBloomTokenizer(DefaultNGramLength, DefaultNGramSkip, 0, NewMetrics(nil))
+	line := "foobarbazz"
+	var blooms []*Bloom
+
+	for i := 0; i < 2; i++ {
+		ch := make(chan *BloomCreation)
+		itr, err := chunkRefItrFromLines(line)
+		require.NoError(t, err)
+		go bt.Populate(
+			NewEmptyIter[*Bloom](),
+			NewSliceIter([]ChunkRefWithIter{
+				{
+					Ref: ChunkRef{},
+					Itr: itr,
+				},
+			}),
+			ch,
+		)
+		var ct int
+		for created := range ch {
+			blooms = append(blooms, created.Bloom)
+			ct++
+		}
+		// ensure we created one bloom for each call
+		require.Equal(t, 1, ct)
+
+	}
+
+	for _, bloom := range blooms {
+		toks := bt.lineTokenizer.Tokens(line)
+		for toks.Next() {
+			token := toks.At()
+			require.True(t, bloom.Test(token))
+		}
+		require.NoError(t, toks.Err())
+	}
+}
+
 func BenchmarkMapClear(b *testing.B) {
 	bt := NewBloomTokenizer(DefaultNGramLength, DefaultNGramSkip, 0, metrics)
 	for i := 0; i < b.N; i++ {