MSEARCH-320 Technical approach to browse Contributors

#1 Browsing by Contributors using dedicated Elasticsearch index

This approach is the same as browsing by contributors, but with a few extensions.

Approach is contains a several steps to implement:

1. Send contributor events from instance to the search.instance-contributor topic (message key = sha1 hash of concatenatination - tenantId + contributorType + key)
2. Implement a new Kafka Listener to listen contributor only events (Kafka will arrange contributors with the same key in the same partition, allowing event processing without optimistic locking)
3. Implement a new InstanceContributor repository with following upsert request for events groups
4. Implement a query which allows to find contributor exact by name and type (it can be CQL with double equal sign, but it looks like that John and John. are threated as the same value (ES standard tokenizer))

Upsert query example:

{
  "script": {
    "source": "def set=new LinkedHashSet(ctx._source.instances);set.addAll(params.ins);params.del.forEach(set::remove);ctx._source.instances=set",
    "lang": "painless",
    "params": {
      "ins": [ "instanceId#1|type#1", "instanceId#2|type#1", "instanceId#3|type#1" ],
	  "del": [ "instanceId#4|type#1"]
    }
  },
  "upsert": {
    "id": "abshc",
    "name": "Antoniou, Grigoris",
    "contributorTypeId": "type#1",
    "instances": [ "instanceId#1|type#1", "instanceId#2|type#1", "instanceId#3|type#1" ]
  }
}

#2 Browsing by Contributors using PostgreSQL table

This options provides ability to browse by using PostgreSQL table with index on the contributors field.

create table instance_contributor
(
    contributor text not null,
    instance_id text not null,
    constraint instance_contributors_pk
        primary key (contributor, instance_id)
);

create index instance_contributors_contributor
    on diku_mod_search.instance_contributors (lower(contributor));

Insertions can be done in batch, which can be done configuring Spring Data Jpa:

insert into instance_contributor(instance_id, contributor) values (?,?) on conflict do nothing;

spring:
  jpa:
    properties:
      hibernate:
        order_inserts: true
        order_updates: true
        jdbc.batch_size: 500

@Data
@Entity
@NoArgsConstructor
@Table(name = "instance_contributors")
@AllArgsConstructor(staticName = "of")
@SQLInsert(sql = "insert into instance_contributors(instance_id, contributor) values (?, ?) on conflict do nothing")
public class InstanceContributorEntity implements Persistable<InstanceContributorEntityId> {

  @EmbeddedId
  private InstanceContributorEntityId id;

  @Override
  public boolean isNew() {
    return true;
  }
}

@Data
@Embeddable
@NoArgsConstructor
@AllArgsConstructor(staticName = "of")
public class InstancecontributorEntityId implements Serializable {

  private String contributor;
  private String instanceId;
}

select contributor, count(*)
from instance_contributors
where contributor in (
  select distinct on (lower(contributor)) contributor
  from instance_contributors
  where lower(contributor) < :anchor
  order by lower(contributor) desc
  limit :limit
)
group by contributor
order by lower(contributor);

select contributor, count(*)
from instance_contributors
where contributor in (
  select distinct on (lower(contributor)) contributor
  from instance_contributors
  where lower(contributor) >= :anchor
  order by lower(contributor)
  limit :limit
)
group by contributor
order by lower(contributor);

#3 Browsing by Contributors using PostgreSQL index and Elasticsearch terms aggregation

This approach can be implemented in two steps:

1. Create new index for lowercase contributor values from instance jsons and browse by it
2. Retrieve counts using terms aggregation per contributor entity

#4 Browse by range query and numeric representation of incoming value

This approach can be based on the Call-Number browsing. The main idea is to create a long value for the string and use it for the range query to limit the number of documents to aggregate.

Items to check/investigate:

• Retrieve number of instances per each contributor
• Manage how to deal with redundant contributors in the result of terms aggregation (script query?)