From d90aaedc0060017c8d17825127a8448797a014ca Mon Sep 17 00:00:00 2001
From: Gani Georgiev <gani.georgiev@gmail.com>
Date: Fri, 1 May 2026 19:16:53 +0300
Subject: [PATCH] skip duplicated records ids from the IN expand

---
 CHANGELOG.md                     |  2 ++
 core/record_query_expand.go      | 13 ++++++++--
 core/record_query_expand_test.go | 42 ++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9d52ba71..3c2e0958 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@
 
 - Reload trusted proxy info UI after settings save.
 
+- Minor expand query optimization that skips the duplicated record ids from the `IN` list.
+
 
 ## v0.37.4
 
diff --git a/core/record_query_expand.go b/core/record_query_expand.go
index 2869c1da..c8472d2d 100644
--- a/core/record_query_expand.go
+++ b/core/record_query_expand.go
@@ -162,11 +162,20 @@ func (app *BaseApp) expandRecords(records []*Record, expandPath string, fetchFun
 
 	// ---------------------------------------------------------------
 
-	// extract the id of the relations to expand
+	// extract the unique ids of the relations to expand
+	// (the initial size assumes that most of the relations are single and unique)
+	existsSet := make(map[string]struct{}, len(records))
 	relIds := make([]string, 0, len(records))
 	for _, record := range records {
-		relIds = append(relIds, record.GetStringSlice(relField.Name)...)
+		ids := record.GetStringSlice(relField.Name)
+		for _, id := range ids {
+			if _, ok := existsSet[id]; !ok {
+				existsSet[id] = struct{}{}
+				relIds = append(relIds, id)
+			}
+		}
 	}
+	existsSet = nil
 
 	// fetch rels
 	rels, relsErr := fetchFunc(relCollection, relIds)
diff --git a/core/record_query_expand_test.go b/core/record_query_expand_test.go
index 04b5cbf1..3e23c509 100644
--- a/core/record_query_expand_test.go
+++ b/core/record_query_expand_test.go
@@ -1,11 +1,15 @@
 package core_test
 
 import (
+	"context"
+	"database/sql"
 	"encoding/json"
 	"errors"
 	"strings"
 	"testing"
+	"time"
 
+	"github.com/pocketbase/dbx"
 	"github.com/pocketbase/pocketbase/core"
 	"github.com/pocketbase/pocketbase/tests"
 	"github.com/pocketbase/pocketbase/tools/list"
@@ -484,3 +488,41 @@ func TestBackRelationExpandSingeVsArrayResult(t *testing.T) {
 		}
 	}
 }
+
+func TestExpandRecordsQuerySkipDuplicatedIds(t *testing.T) {
+	t.Parallel()
+
+	app, _ := tests.NewTestApp()
+	defer app.Cleanup()
+
+	// fetch records that are known to have at least 1 common relation between them
+	records, err := app.FindRecordsByIds("demo1", []string{"84nmscqy84lsi1t", "al1h9ijdeojtsjy"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// log selects
+	concurrentQueries := []string{}
+	app.ConcurrentDB().(*dbx.DB).QueryLogFunc = func(ctx context.Context, t time.Duration, sql string, rows *sql.Rows, err error) {
+		concurrentQueries = append(concurrentQueries, sql)
+	}
+	app.ConcurrentDB().(*dbx.DB).ExecLogFunc = func(ctx context.Context, t time.Duration, sql string, result sql.Result, err error) {
+		concurrentQueries = append(concurrentQueries, sql)
+	}
+
+	// expand
+	failed := app.ExpandRecords(records, []string{"rel_many"}, nil)
+	if len(failed) > 0 {
+		t.Fatalf("Expected no expand errors, got %v", failed)
+	}
+
+	if len(concurrentQueries) != 1 {
+		t.Fatalf("Expected exactly 1 expand query, got %d:\n%v", len(concurrentQueries), concurrentQueries)
+	}
+
+	// "oap640cot4yru2s" is used in both relations but must exists only once
+	expected := "SELECT `users`.* FROM `users` WHERE `users`.`id` IN ('oap640cot4yru2s', 'bgs820n361vj1qd', '4q1xlclmfloku33')"
+	if concurrentQueries[0] != expected {
+		t.Fatalf("Expected query\n%v\ngot\n%v", expected, concurrentQueries[0])
+	}
+}