Rework suggestion backend (#33538)

Fix #33522 

The suggestion backend logic now is

- If the keyword is empty, returned the latest 5 issues/prs with index
desc order
- If the keyword is digital, find all issues/prs which `index` has a
prefix with that, with index asc order
- If the keyword is non-digital or if the queried records less than 5,
searching issues/prs title with a `like`, with index desc order

## Empty keyword
<img width="310" alt="image"
src="https://github.com/user-attachments/assets/1912c634-0d98-4eeb-8542-d54240901f77"
/>

## Digital
<img width="479" alt="image"
src="https://github.com/user-attachments/assets/0356a936-7110-4a24-b21e-7400201bf9b8"
/>

## Digital and title contains the digital
<img width="363" alt="image"
src="https://github.com/user-attachments/assets/6e12f908-28fe-48de-8ccc-09cbeab024d4"
/>

## non-Digital
<img width="435" alt="image"
src="https://github.com/user-attachments/assets/2722bb53-baa2-4d67-a224-522a65f73856"
/>
<img width="477" alt="image"
src="https://github.com/user-attachments/assets/06708dd9-80d1-4a88-b32b-d29072dd1ba6"
/>

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

models/issues/issue.go

@@ -17,6 +17,7 @@ import (
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/container"
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/optional"
 	"code.gitea.io/gitea/modules/setting"
 	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/timeutil"
@@ -501,6 +502,45 @@ func GetIssueByIndex(ctx context.Context, repoID, index int64) (*Issue, error) {
 	return issue, nil
 }
 
+func isPullToCond(isPull optional.Option[bool]) builder.Cond {
+	if isPull.Has() {
+		return builder.Eq{"is_pull": isPull.Value()}
+	}
+	return builder.NewCond()
+}
+
+func FindLatestUpdatedIssues(ctx context.Context, repoID int64, isPull optional.Option[bool], pageSize int) (IssueList, error) {
+	issues := make([]*Issue, 0, pageSize)
+	err := db.GetEngine(ctx).Where("repo_id = ?", repoID).
+		And(isPullToCond(isPull)).
+		OrderBy("updated_unix DESC").
+		Limit(pageSize).
+		Find(&issues)
+	return issues, err
+}
+
+func FindIssuesSuggestionByKeyword(ctx context.Context, repoID int64, keyword string, isPull optional.Option[bool], excludedID int64, pageSize int) (IssueList, error) {
+	cond := builder.NewCond()
+	if excludedID > 0 {
+		cond = cond.And(builder.Neq{"`id`": excludedID})
+	}
+
+	// It seems that GitHub searches both title and content (maybe sorting by the search engine's ranking system?)
+	// The first PR (https://github.com/go-gitea/gitea/pull/32327) uses "search indexer" to search "name(title) +  content"
+	// But it seems that searching "content" (especially LIKE by DB engine) generates worse (unusable) results.
+	// So now (https://github.com/go-gitea/gitea/pull/33538) it only searches "name(title)", leave the improvements to the future.
+	cond = cond.And(db.BuildCaseInsensitiveLike("`name`", keyword))
+
+	issues := make([]*Issue, 0, pageSize)
+	err := db.GetEngine(ctx).Where("repo_id = ?", repoID).
+		And(isPullToCond(isPull)).
+		And(cond).
+		OrderBy("updated_unix DESC, `index` DESC").
+		Limit(pageSize).
+		Find(&issues)
+	return issues, err
+}
+
 // GetIssueWithAttrsByIndex returns issue by index in a repository.
 func GetIssueWithAttrsByIndex(ctx context.Context, repoID, index int64) (*Issue, error) {
 	issue, err := GetIssueByIndex(ctx, repoID, index)

routers/web/repo/issue_suggestions.go

@@ -6,13 +6,10 @@ package repo
 import (
 	"net/http"
 
-	"code.gitea.io/gitea/models/db"
-	issues_model "code.gitea.io/gitea/models/issues"
 	"code.gitea.io/gitea/models/unit"
-	issue_indexer "code.gitea.io/gitea/modules/indexer/issues"
 	"code.gitea.io/gitea/modules/optional"
-	"code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/services/context"
+	issue_service "code.gitea.io/gitea/services/issue"
 )
 
 // IssueSuggestions returns a list of issue suggestions
@@ -29,54 +26,11 @@ func IssueSuggestions(ctx *context.Context) {
 		isPull = optional.Some(false)
 	}
 
-	searchOpt := &issue_indexer.SearchOptions{
-		Paginator: &db.ListOptions{
-			Page:     0,
-			PageSize: 5,
-		},
-		Keyword:  keyword,
-		RepoIDs:  []int64{ctx.Repo.Repository.ID},
-		IsPull:   isPull,
-		IsClosed: nil,
-		SortBy:   issue_indexer.SortByUpdatedDesc,
-	}
-
-	ids, _, err := issue_indexer.SearchIssues(ctx, searchOpt)
-	if err != nil {
-		ctx.ServerError("SearchIssues", err)
-		return
-	}
-	issues, err := issues_model.GetIssuesByIDs(ctx, ids, true)
+	suggestions, err := issue_service.GetSuggestion(ctx, ctx.Repo.Repository, isPull, keyword)
 	if err != nil {
-		ctx.ServerError("FindIssuesByIDs", err)
+		ctx.ServerError("GetSuggestion", err)
 		return
 	}
 
-	suggestions := make([]*structs.Issue, 0, len(issues))
-
-	for _, issue := range issues {
-		suggestion := &structs.Issue{
-			ID:    issue.ID,
-			Index: issue.Index,
-			Title: issue.Title,
-			State: issue.State(),
-		}
-
-		if issue.IsPull {
-			if err := issue.LoadPullRequest(ctx); err != nil {
-				ctx.ServerError("LoadPullRequest", err)
-				return
-			}
-			if issue.PullRequest != nil {
-				suggestion.PullRequest = &structs.PullRequestMeta{
-					HasMerged:        issue.PullRequest.HasMerged,
-					IsWorkInProgress: issue.PullRequest.IsWorkInProgress(ctx),
-				}
-			}
-		}
-
-		suggestions = append(suggestions, suggestion)
-	}
-
 	ctx.JSON(http.StatusOK, suggestions)
 }

services/issue/suggestion.go

@@ -0,0 +1,73 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package issue
+
+import (
+	"context"
+	"strconv"
+
+	issues_model "code.gitea.io/gitea/models/issues"
+	repo_model "code.gitea.io/gitea/models/repo"
+	"code.gitea.io/gitea/modules/optional"
+	"code.gitea.io/gitea/modules/structs"
+)
+
+func GetSuggestion(ctx context.Context, repo *repo_model.Repository, isPull optional.Option[bool], keyword string) ([]*structs.Issue, error) {
+	var issues issues_model.IssueList
+	var err error
+	pageSize := 5
+	if keyword == "" {
+		issues, err = issues_model.FindLatestUpdatedIssues(ctx, repo.ID, isPull, pageSize)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		indexKeyword, _ := strconv.ParseInt(keyword, 10, 64)
+		var issueByIndex *issues_model.Issue
+		var excludedID int64
+		if indexKeyword > 0 {
+			issueByIndex, err = issues_model.GetIssueByIndex(ctx, repo.ID, indexKeyword)
+			if err != nil && !issues_model.IsErrIssueNotExist(err) {
+				return nil, err
+			}
+			if issueByIndex != nil {
+				excludedID = issueByIndex.ID
+				pageSize--
+			}
+		}
+
+		issues, err = issues_model.FindIssuesSuggestionByKeyword(ctx, repo.ID, keyword, isPull, excludedID, pageSize)
+		if err != nil {
+			return nil, err
+		}
+
+		if issueByIndex != nil {
+			issues = append([]*issues_model.Issue{issueByIndex}, issues...)
+		}
+	}
+
+	if err := issues.LoadPullRequests(ctx); err != nil {
+		return nil, err
+	}
+
+	suggestions := make([]*structs.Issue, 0, len(issues))
+	for _, issue := range issues {
+		suggestion := &structs.Issue{
+			ID:    issue.ID,
+			Index: issue.Index,
+			Title: issue.Title,
+			State: issue.State(),
+		}
+
+		if issue.IsPull && issue.PullRequest != nil {
+			suggestion.PullRequest = &structs.PullRequestMeta{
+				HasMerged:        issue.PullRequest.HasMerged,
+				IsWorkInProgress: issue.PullRequest.IsWorkInProgress(ctx),
+			}
+		}
+		suggestions = append(suggestions, suggestion)
+	}
+
+	return suggestions, nil
+}

services/issue/suggestion_test.go

@@ -0,0 +1,57 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package issue
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/db"
+	repo_model "code.gitea.io/gitea/models/repo"
+	"code.gitea.io/gitea/models/unittest"
+	"code.gitea.io/gitea/modules/optional"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_Suggestion(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	repo1 := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: 1})
+
+	testCases := []struct {
+		keyword         string
+		isPull          optional.Option[bool]
+		expectedIndexes []int64
+	}{
+		{
+			keyword:         "",
+			expectedIndexes: []int64{5, 1, 4, 2, 3},
+		},
+		{
+			keyword:         "1",
+			expectedIndexes: []int64{1},
+		},
+		{
+			keyword:         "issue",
+			expectedIndexes: []int64{4, 1, 2, 3},
+		},
+		{
+			keyword:         "pull",
+			expectedIndexes: []int64{5},
+		},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(testCase.keyword, func(t *testing.T) {
+			issues, err := GetSuggestion(db.DefaultContext, repo1, testCase.isPull, testCase.keyword)
+			assert.NoError(t, err)
+
+			issueIndexes := make([]int64, 0, len(issues))
+			for _, issue := range issues {
+				issueIndexes = append(issueIndexes, issue.Index)
+			}
+			assert.EqualValues(t, testCase.expectedIndexes, issueIndexes)
+		})
+	}
+}