4 files changed, 54 insertions, 2 deletions
diff --git a/modules/indexer/issues/db/db.go b/modules/indexer/issues/db/db.go
index 05ec548435..6c9cfcf670 100644
--- a/modules/indexer/issues/db/db.go
+++ b/modules/indexer/issues/db/db.go
@@ -71,6 +71,12 @@ func (i *Indexer) Search(ctx context.Context, options *internal.SearchOptions) (
 				)),
 			),
 		)
+
+		if options.IsKeywordNumeric() {
+			cond = cond.Or(
+				builder.Eq{"`index`": options.Keyword},
+			)
+		}
 	}
 
 	opt, err := ToDBOptions(ctx, options)
diff --git a/modules/indexer/issues/indexer.go b/modules/indexer/issues/indexer.go
index 1cb86feb82..c82dc0867e 100644
--- a/modules/indexer/issues/indexer.go
+++ b/modules/indexer/issues/indexer.go
@@ -283,9 +283,9 @@ const (
 func SearchIssues(ctx context.Context, opts *SearchOptions) ([]int64, int64, error) {
 	indexer := *globalIndexer.Load()
 
-	if opts.Keyword == "" {
+	if opts.Keyword == "" || opts.IsKeywordNumeric() {
 		// This is a conservative shortcut.
-		// If the keyword is empty, db has better (at least not worse) performance to filter issues.
+		// If the keyword is empty or an integer, db has better (at least not worse) performance to filter issues.
 		// When the keyword is empty, it tends to listing rather than searching issues.
 		// So if the user creates an issue and list issues immediately, the issue may not be listed because the indexer needs time to index the issue.
 		// Even worse, the external indexer like elastic search may not be available for a while,
diff --git a/modules/indexer/issues/indexer_test.go b/modules/indexer/issues/indexer_test.go
index e426229f78..4986d8d294 100644
--- a/modules/indexer/issues/indexer_test.go
+++ b/modules/indexer/issues/indexer_test.go
@@ -31,6 +31,7 @@ func TestDBSearchIssues(t *testing.T) {
 	InitIssueIndexer(true)
 
 	t.Run("search issues with keyword", searchIssueWithKeyword)
+	t.Run("search issues by index", searchIssueByIndex)
 	t.Run("search issues in repo", searchIssueInRepo)
 	t.Run("search issues by ID", searchIssueByID)
 	t.Run("search issues is pr", searchIssueIsPull)
@@ -87,6 +88,43 @@ func searchIssueWithKeyword(t *testing.T) {
 	}
 }
 
+func searchIssueByIndex(t *testing.T) {
+	tests := []struct {
+		opts        SearchOptions
+		expectedIDs []int64
+	}{
+		{
+			SearchOptions{
+				Keyword: "1000",
+				RepoIDs: []int64{1},
+			},
+			[]int64{},
+		},
+		{
+			SearchOptions{
+				Keyword: "2",
+				RepoIDs: []int64{1, 2, 3, 32},
+			},
+			[]int64{17, 12, 7, 2},
+		},
+		{
+			SearchOptions{
+				Keyword: "1",
+				RepoIDs: []int64{58},
+			},
+			[]int64{19},
+		},
+	}
+
+	for _, test := range tests {
+		issueIDs, _, err := SearchIssues(context.TODO(), &test.opts)
+		if !assert.NoError(t, err) {
+			return
+		}
+		assert.Equal(t, test.expectedIDs, issueIDs)
+	}
+}
+
 func searchIssueInRepo(t *testing.T) {
 	tests := []struct {
 		opts        SearchOptions
diff --git a/modules/indexer/issues/internal/model.go b/modules/indexer/issues/internal/model.go
index 2dfee8b72e..a43c6be005 100644
--- a/modules/indexer/issues/internal/model.go
+++ b/modules/indexer/issues/internal/model.go
@@ -4,6 +4,8 @@
 package internal
 
 import (
+	"strconv"
+
 	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/modules/optional"
 	"code.gitea.io/gitea/modules/timeutil"
@@ -124,6 +126,12 @@ func (o *SearchOptions) Copy(edit ...func(options *SearchOptions)) *SearchOption
 	return &v
 }
 
+// used for optimized issue index based search
+func (o *SearchOptions) IsKeywordNumeric() bool {
+	_, err := strconv.Atoi(o.Keyword)
+	return err == nil
+}
+
 type SortBy string
 
 const (