jjeong

Of course, just having more replica shards on the same number of nodes doesn’t increase our performance at all because each shard has access to a smaller fraction of its node’s resources. You need to add hardware to increase throughput.

- 같은 노드 수에 replica shard만 늘린다고 성능이 좋아 지지 않는다.

- 성능을 향상 시키고 싶으면 장비를 더 넣어라.

One node in the cluster is elected to be the master node, which is in charge of managing cluster-wide changes like creating or deleting an index, or adding or removing a node from the cluster. The master node does not need to be involved in document-level changes or searches, which means that having just one master node will not become a bottleneck as traffic grows. Any node can become the master. Our example cluster has only one node, so it performs the master role.

인덱스 생성/삭제

노드 추가/제거

문서 레벨의 변경 작업

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You may already have noticed that the word index is overloaded with several meanings in the context of Elasticsearch. A little clarification is necessary:

Index (noun)

As explained previously, an index is like a database in a traditional relational database. It is the place to store related documents. The plural of index is indices or indexes.

Index (verb)

To index a document is to store a document in an index (noun) so that it can be retrieved and queried. It is much like the INSERT keyword in SQL except that, if the document already

exists, the new document would replace the old.

Inverted index

Relational databases add an index, such as a B-tree index, to specific columns in order to improve the speed of data retrieval. Elasticsearch and Lucene use a structure called an inv

erted index for exactly the same purpose.

By default, every field in a document is indexed (has an inverted index) and thus is searchable. A field without an inverted index is not searchable. We discuss inverted indexes in m

ore detail in Inverted Index.