Performance: Add preallocation for some slices (#59593)

pkg/services/alerting/conditions/query.go

@@ -1,6 +1,7 @@
 package conditions
 
 import (
+	gocontext "context"
 	"errors"
 	"fmt"
 	"strings"
@@ -10,8 +11,6 @@ import (
 	"github.com/grafana/grafana/pkg/tsdb/legacydata/interval"
 	"github.com/grafana/grafana/pkg/tsdb/prometheus"
 
-	gocontext "context"
-
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 
 	"github.com/grafana/grafana/pkg/components/null"
@@ -61,7 +60,7 @@ func (c *QueryCondition) Eval(context *alerting.EvalContext, requestHandler lega
 	// matches represents all the series that violate the alert condition
 	var matches []*alerting.EvalMatch
 	// allMatches capture all evaluation matches irregardless on whether the condition is met or not
-	var allMatches []*alerting.EvalMatch
+	allMatches := make([]*alerting.EvalMatch, 0, len(seriesList))
 
 	for _, series := range seriesList {
 		reducedValue := c.Reducer.Reduce(series)

pkg/services/alerting/notifiers/googlechat.go

@@ -144,6 +144,7 @@ func (gcn *GoogleChatNotifier) Notify(evalContext *alerting.EvalContext) error {
 	}
 
 	// add a text paragraph widget for the fields
+	//nolint:prealloc // break block
 	var fields []textParagraphWidget
 	fieldLimitCount := 4
 	for index, evt := range evalContext.EvalMatches {