The attached patch should fixes the issue.
Below are the results tested on a project with 7 members.
Current code:
redmine-app(dev)> t = TimeEntry.first
TimeEntry Load (0.1ms) SELECT "time_entries".* FROM "time_entries" ORDER BY "time_entries"."id" ASC LIMIT ? [["LIMIT", 1]]
=>
#<TimeEntry:0x000000016c1f2df0
...
redmine-app(dev)> t.assignable_users
Project Load (0.1ms) SELECT "projects".* FROM "projects" WHERE "projects"."id" = ? LIMIT ? [["id", 1], ["LIMIT", 1]]
Member Load (0.1ms) SELECT "members".* FROM "members" INNER JOIN "users" ON "users"."id" = "members"."user_id" WHERE "members"."project_id" = ? AND "users"."type" = ? AND "users"."status" = ? AND "users"."status" = ? [["project_id", 1], ["type", "User"], ["status", 1], ["status", 1]]
User Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."type" = ? AND "users"."id" IN (?, ?, ?, ?, ?, ?, ?) [["type", "User"], ["id", 2], ["id", 3], ["id", 1], ["id", 4], ["id", 7], ["id", 8], ["id", 9]]
EnabledModule Pluck (0.4ms) SELECT "enabled_modules"."name" FROM "enabled_modules" WHERE "enabled_modules"."project_id" = ? [["project_id", 1]]
Member Load (0.1ms) SELECT "members".* FROM "members" INNER JOIN "projects" ON "projects"."id" = "members"."project_id" WHERE "members"."user_id" = ? AND "projects"."status" != ? AND "members"."project_id" = ? ORDER BY "members"."id" ASC LIMIT ? [["user_id", 2], ["status", 9], ["project_id", 1], ["LIMIT", 1]]
Role Load (0.1ms) SELECT DISTINCT "roles".* FROM "roles" INNER JOIN "member_roles" ON "roles"."id" = "member_roles"."role_id" WHERE "member_roles"."member_id" = ? [["member_id", 1]]
Member Load (0.2ms) SELECT "members".* FROM "members" INNER JOIN "projects" ON "projects"."id" = "members"."project_id" WHERE "members"."user_id" = ? AND "projects"."status" != ? AND "members"."project_id" = ? ORDER BY "members"."id" ASC LIMIT ? [["user_id", 3], ["status", 9], ["project_id", 1], ["LIMIT", 1]]
Role Load (0.0ms) SELECT DISTINCT "roles".* FROM "roles" INNER JOIN "member_roles" ON "roles"."id" = "member_roles"."role_id" WHERE "member_roles"."member_id" = ? [["member_id", 2]]
Member Load (0.0ms) SELECT "members".* FROM "members" INNER JOIN "projects" ON "projects"."id" = "members"."project_id" WHERE "members"."user_id" = ? AND "projects"."status" != ? AND "members"."project_id" = ? ORDER BY "members"."id" ASC LIMIT ? [["user_id", 4], ["status", 9], ["project_id", 1], ["LIMIT", 1]]
Role Load (0.0ms) SELECT DISTINCT "roles".* FROM "roles" INNER JOIN "member_roles" ON "roles"."id" = "member_roles"."role_id" WHERE "member_roles"."member_id" = ? [["member_id", 38]]
Member Load (0.0ms) SELECT "members".* FROM "members" INNER JOIN "projects" ON "projects"."id" = "members"."project_id" WHERE "members"."user_id" = ? AND "projects"."status" != ? AND "members"."project_id" = ? ORDER BY "members"."id" ASC LIMIT ? [["user_id", 7], ["status", 9], ["project_id", 1], ["LIMIT", 1]]
Role Load (0.0ms) SELECT DISTINCT "roles".* FROM "roles" INNER JOIN "member_roles" ON "roles"."id" = "member_roles"."role_id" WHERE "member_roles"."member_id" = ? [["member_id", 39]]
Member Load (0.0ms) SELECT "members".* FROM "members" INNER JOIN "projects" ON "projects"."id" = "members"."project_id" WHERE "members"."user_id" = ? AND "projects"."status" != ? AND "members"."project_id" = ? ORDER BY "members"."id" ASC LIMIT ? [["user_id", 8], ["status", 9], ["project_id", 1], ["LIMIT", 1]]
Role Load (0.0ms) SELECT DISTINCT "roles".* FROM "roles" INNER JOIN "member_roles" ON "roles"."id" = "member_roles"."role_id" WHERE "member_roles"."member_id" = ? [["member_id", 40]]
Member Load (0.0ms) SELECT "members".* FROM "members" INNER JOIN "projects" ON "projects"."id" = "members"."project_id" WHERE "members"."user_id" = ? AND "projects"."status" != ? AND "members"."project_id" = ? ORDER BY "members"."id" ASC LIMIT ? [["user_id", 9], ["status", 9], ["project_id", 1], ["LIMIT", 1]]
Role Load (0.0ms) SELECT DISTINCT "roles".* FROM "roles" INNER JOIN "member_roles" ON "roles"."id" = "member_roles"."role_id" WHERE "member_roles"."member_id" = ? [["member_id", 41]]
AnonymousUser Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."type" = ? AND "users"."lastname" = ? LIMIT ? [["type", "AnonymousUser"], ["lastname", "Anonymous"], ["LIMIT", 1]]
With the patch applied:
redmine-app(dev)> t = TimeEntry.first
TimeEntry Load (0.4ms) SELECT "time_entries".* FROM "time_entries" ORDER BY "time_entries"."id" ASC LIMIT ? [["LIMIT", 1]]
=>
#<TimeEntry:0x000000030b457f00
...
redmine-app(dev)> t.assignable_users
Project Load (0.4ms) SELECT "projects".* FROM "projects" WHERE "projects"."id" = ? LIMIT ? [["id", 1], ["LIMIT", 1]]
Member Load (0.3ms) SELECT "members".* FROM "members" INNER JOIN "users" ON "users"."id" = "members"."user_id" WHERE "members"."project_id" = ? AND "users"."type" = ? AND "users"."status" = ? AND "users"."status" = ? [["project_id", 1], ["type", "User"], ["status", 1], ["status", 1]]
MemberRole Load (0.1ms) SELECT "member_roles".* FROM "member_roles" WHERE "member_roles"."member_id" IN (?, ?, ?, ?, ?, ?, ?) [["member_id", 1], ["member_id", 2], ["member_id", 37], ["member_id", 38], ["member_id", 39], ["member_id", 40], ["member_id", 41]]
Role Load (0.1ms) SELECT DISTINCT "roles".* FROM "roles" WHERE "roles"."id" IN (?, ?) [["id", 1], ["id", 2]]
User Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."type" = ? AND "users"."id" IN (?, ?, ?, ?, ?, ?, ?) [["type", "User"], ["id", 2], ["id", 3], ["id", 1], ["id", 4], ["id", 7], ["id", 8], ["id", 9]]
AnonymousUser Load (0.1ms) SELECT "users".* FROM "users" WHERE "users"."type" = ? AND "users"."lastname" = ? LIMIT ? [["type", "AnonymousUser"], ["lastname", "Anonymous"], ["LIMIT", 1]]
Updated by 
Updated by 
