How to handle a Hibernate multi-field search query on nullable child entities - spring-boot

Question

Using Spring Boot Web & Data JPA (2.3.1) with QueryDSL with PostgreSQL 11, we are trying to implement a custom search for a UI table on an entity with two #ManyToOne child entities. The idea is to be able to provide a single search input field and search for that string (like or contains ignore case) across multiple String fields across the entities' fields and also provide paging. During UI POCs, we were originally pulling the entire list and having the web UI provide this exact search functionality but that will not be sustainable in the future.
My original thought was something to this effect:
/devices?externalId={{val}}&site.externalId={{val}}&organization.name={{val}}&size=10
but the more human readable intent was:
externalId={{val}} OR site.externalId={{val}} OR organization.name={{val}} WITH size=10
I tried implementing it with QueryDSL's Web Bindings (hence the above example) with a QuerydslBinderCustomizer but it didn't work. Then I realized that it doesn't provide much for this particular situation so I moved to a JpaRepository with an #Query and shortened the URL to.
/devices?search={{val}}&size=10
Either way, what seems to be happening is that if, for example, device.site is null, the entire result is always zero. Even if device.organization or device.site is null, I would expect results where the device.externalId matches the search value criteria. If I remove support for site.externalId, then it works; I get results matching the device.externalId. I also tried this on a database with devices with non-null site references and that also worked. So the issue seems to be centered around null child entities.
Quick Scenario:
Note: Device in JSON format and id's in non-UUID format for brevity.
{
"id" : "a",
"externalId" : "VTD1002",
"site" : null
},
{
"id" : "b",
"externalId" : "VTD_1000",
"site" : { "externalId" : "VTS_1000" }
},
{
"id" : "c",
"externalId" : "VFD_1000"
"site" : { "externalId" : "VFS_1000" }
}
Pseudo Tests:
search = "t" -> resulting IDs = a, b
Only a and b have a T
search = "Z" -> resulting IDs =
None have Z
search = "1" -> resulting IDs = a, b, c
All have a 1
search = "2" -> resulting IDs = a
Only a has a 2
Entities
Note: redacted from original for brevity
#Entity
#Data #Builder
#Table(name = "devices")
#EqualsAndHashCode(of = "id")
#NoArgsConstructor #AllArgsConstructor
public class Device {
#Id
#GeneratedValue
private UUID id;
private String externalId;
#ManyToOne
private Product product;
#ManyToOne
private Site site;
}
#Entity
#Data #Builder
#Table(name = "organizations")
#EqualsAndHashCode(of = "id")
#NoArgsConstructor #AllArgsConstructor
public class Organization {
#Id
#GeneratedValue
private UUID id;
private String name;
#ToString.Exclude
#OneToMany(mappedBy = "organization")
private Set<Device> devices;
}
#Entity
#Data #Builder
#NoArgsConstructor
#AllArgsConstructor
#EqualsAndHashCode(of = "id")
#Table(name = "sites")
public class Site {
#Id
#GeneratedValue
private UUID id;
private String externalId;
#OneToMany(cascade = CascadeType.ALL, mappedBy = "site")
private Set<Device> devices;
}
Here's the latest I've tried without luck:
#Query("from Device d where (d.externalId like lower(:search)) or (d.site.id is not null and d.site.externalId like lower(:search)) or (d.organization.id is not null and d.organization.externalId like lower(:search))")
Page<Device> search(String search, Pageable pageable);
The idea was to check for the device's site_id reference on the table before even trying to evaluate the Site's externalId. Removing the is not null didn't make a difference and going d.site is not null also didn't work.
I think what's happening is that the native SQL that is generated is causing things to go awry. I suspect the issue is in the cross joins but after a few days of searching, any clues or insights would be appreciated.
select
device0_.id as id1_3_,
device0_.external_id as external3_3_,
device0_.organization_id as organiz13_3_,
device0_.site_id as site_id15_3_,
from
devices device0_ cross
join
sites site1_ cross
join
organizations organizati2_
where
device0_.site_id=site1_.id
and device0_.organization_id=organizati2_.id
and (
device0_.external_id like lower(?)
or (
device0_.site_id is not null
)
and (
site1_.external_id like lower(?)
)
or (
device0_.organization_id is not null
)
and (
organizati2_.external_id like lower(?)
)
) limit ?

Answer 1

The problem as you can see is that Hibernate uses inner joins for your implicit joins, which is forced onto it by JPA. Having said that, you will have to use left joins like this to make this null-aware stuff work
#Query("from Device d left join d.site s left join d.organization o where (d.externalId like lower(:search)) or (s.id is not null and s.externalId like lower(:search)) or (o.id is not null and o.externalId like lower(:search))")
Page<Device> search(String search, Pageable pageable);

Answer 2

With #christian-beikov help, I was able to get pass the nullability piece. However, I had to modify the query to get it working all the way through to the web controller.
#Query("select d from Device d left join d.site s left join d.organization o "
+ "where lower(d.externalId) like concat('%', lower(:search),'%')"
+ "or lower(s.externalId) like concat('%', lower(:search),'%')"
+ "or lower(o.externalId) like concat('%', lower(:search),'%')")
Page<Device> focusedSearchByValue(String search, Pageable pageable);
I had to add select d so that I would get back a list of Devices and not of Object.
I then had to make sure both the search term and the target column value of were in lower-case so that the comparison is "apples to apples".
Finally, I added the equivalent of ilike %{search}% because apparently there is no HQL support for ilike.
As a side note, for experimentation purposes, I also looked at what this equivalent approach generated to further explore the problem.
Page<Device> findAllByExternalIdContainsOrSiteExternalIdContainsOrOrganizationNameContains(String v1, String v2, String v3, Pageable pageable);