perf(chstorage): query labels and label values from deduplicated reso…

…urce

internal/chstorage/querier_logs.go

@@ -3,6 +3,7 @@ package chstorage
 import (
 	"context"
 	"slices"
+	"time"
 
 	"github.com/ClickHouse/ch-go/proto"
 	"github.com/go-faster/errors"
@@ -60,15 +61,15 @@ func (q *Querier) LabelNames(ctx context.Context, opts logstorage.LabelsOptions)
 		}
 	)
 	if err := q.do(ctx, selectQuery{
-		Query: chsql.Select(table,
+		Query: chsql.SelectFrom(
+			// Select deduplicated resources from subquery.
+			q.deduplicatedResource(table, opts.Start, opts.End),
 			chsql.ResultColumn{
 				Name: "name",
 				Expr: chsql.ArrayJoin(attrKeys(colResource)),
 				Data: &name,
-			},
-		).
+			}).
 			Distinct(true).
-			Where(chsql.InTimeRange("timestamp", opts.Start, opts.End)).
 			Limit(q.labelLimit),
 		OnResult: func(ctx context.Context, block proto.Block) error {
 			for i := 0; i < name.Rows(); i++ {
@@ -162,22 +163,24 @@ func (q *Querier) LabelValues(ctx context.Context, labelName string, opts logsto
 			labelName = key
 		}
 
+		resourceQuery := q.deduplicatedResource(table, opts.Start, opts.End)
+		for _, m := range opts.Query.Matchers {
+			resourceQuery.Where(q.logQLLabelMatcher(m, mapping))
+		}
 		var (
 			value proto.ColStr
-			query = chsql.Select(table, chsql.ResultColumn{
-				Name: "value",
-				Expr: attrSelector(colResource, labelName),
-				Data: &value,
-			}).
+			query = chsql.SelectFrom(
+				// Select deduplicated resources from subquery.
+				resourceQuery,
+				chsql.ResultColumn{
+					Name: "value",
+					Expr: attrSelector(colResource, labelName),
+					Data: &value,
+				}).
 				Distinct(true).
-				Where(chsql.InTimeRange("timestamp", opts.Start, opts.End))
+				Order(chsql.Ident("value"), chsql.Asc).
+				Limit(q.labelLimit)
 		)
-		for _, m := range opts.Query.Matchers {
-			query.Where(q.logQLLabelMatcher(m, mapping))
-		}
-		query.Order(chsql.Ident("value"), chsql.Asc).
-			Limit(q.labelLimit)
-
 		if err := q.do(ctx, selectQuery{
 			Query: query,
 			OnResult: func(ctx context.Context, block proto.Block) error {
@@ -390,6 +393,15 @@ func (q *Querier) Series(ctx context.Context, opts logstorage.SeriesOptions) (re
 	return result, nil
 }
 
+func (q *Querier) deduplicatedResource(table string, start, end time.Time) *chsql.SelectQuery {
+	// Select deduplicated resource by using GROUP BY, since DISTINCT is not optimized by Clickhouse.
+	//
+	// See https://github.com/ClickHouse/ClickHouse/issues/4670
+	return chsql.Select(table, chsql.Column(colResource, nil)).
+		GroupBy(chsql.Ident(colResource)).
+		Where(chsql.InTimeRange("timestamp", start, end))
+}
+
 func forEachColMap[K comparable, V any](c *proto.ColMap[K, V], row int, cb func(K, V)) {
 	var start int
 	end := int(c.Offsets[row])