尝试在 Elasticsearch 中设置 max_gram 和 min_gram

Question

我试图在 Ubuntu 16.04 EC2 服务器上部署一个 Ruby on Rails 应用程序，但给出了一个关于 Elasticsearch 上 max_gram 和 min_gram 之间差异的错误，我还没有任何使用 Elasticsearch 的经验，所以我完全迷失在这里，我需要一些指导这样做并学习如何设置它以避免将来出现此问题。

我第一次进行部署时出现拒绝连接到 localhost:9200 的错误，因此我必须检查服务是否正在运行，甚至检查防火墙，最后我必须进行全新安装并在 elasticsearch 上配置所有内容。 yml 现在正在运行和工作，但是当我尝试再次部署时出现错误，在互联网上进行了大量搜索，有很多文档，但我仍然不知道在哪里设置这些值。

这是我在日志中得到的错误：

-----> Migrating database...
rake aborted!
StandardError: An error has occurred, all later migrations canceled:

[400] {"error":{"root_cause":[{"type":"illegal_argument_exception","reason":"The difference between max_gram and min_gram in NGram Tokenizer must be less than or equal to: [1] but was [49]. This limit can be set by changing the [index.max_ngram_diff] index level setting."}],"type":"illegal_argument_exception","reason":"The difference between max_gram and min_gram in NGram Tokenizer must be less than or equal to: [1] but was [49]. This limit can be set by changing the [index.max_ngram_diff] index level setting."},"status":400}
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/elasticsearch-transport-6.0.2/lib/elasticsearch/transport/transport/base.rb:205:in `__raise_transport_error'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/elasticsearch-transport-6.0.2/lib/elasticsearch/transport/transport/base.rb:323:in `perform_request'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/elasticsearch-transport-6.0.2/lib/elasticsearch/transport/transport/http/faraday.rb:20:in `perform_request'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/elasticsearch-transport-6.0.2/lib/elasticsearch/transport/client.rb:131:in `perform_request'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/elasticsearch-api-6.0.2/lib/elasticsearch/api/namespace/common.rb:21:in `perform_request'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/elasticsearch-api-6.0.2/lib/elasticsearch/api/actions/indices/create.rb:86:in `create'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/searchkick-3.0.2/lib/searchkick/index.rb:16:in `create'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/searchkick-3.0.2/lib/searchkick/index.rb:203:in `create_index'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/searchkick-3.0.2/lib/searchkick/index.rb:270:in `reindex_scope'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/searchkick-3.0.2/lib/searchkick/index.rb:196:in `reindex'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/searchkick-3.0.2/lib/searchkick/model.rb:59:in `searchkick_reindex'
/home/deploy/catalogindustry/releases/20190807135404/db/migrate/20180405153226_validated_true.rb:4:in `change'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:789:in `exec_migration'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:773:in `block (2 levels) in migrate'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:772:in `block in migrate'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/connection_adapters/abstract/connection_pool.rb:398:in `with_connection'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:771:in `migrate'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:951:in `migrate'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:1232:in `block in execute_migration_in_transaction'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:1302:in `ddl_transaction'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:1231:in `execute_migration_in_transaction'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:1203:in `block in migrate_without_lock'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:1202:in `each'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:1202:in `migrate_without_lock'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:1150:in `block in migrate'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:1319:in `with_advisory_lock'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:1150:in `migrate'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:1006:in `up'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/migration.rb:984:in `migrate'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/tasks/database_tasks.rb:163:in `migrate'
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/activerecord-5.0.7/lib/active_record/railties/databases.rake:58:in `block (2 levels) in '
/home/deploy/catalogindustry/shared/bundle/ruby/2.3.0/gems/rake-12.3.1/exe/rake:27:in `'
/home/deploy/.rbenv/versions/2.3.1/bin/bundle:23:in `load'
/home/deploy/.rbenv/versions/2.3.1/bin/bundle:23:in `

elasticsearch 上没有索引文件，默认模板上没有关于此设置的任何内容

Answer 1

我遇到了类似的问题，下面的错误消息清楚地解释了这个问题。

[400] {"error":{"root_cause":[{"type":"illegal_argument_exception","re​​ason":"NGram Tokenizer 中 max_gram 和 min_gram 的差值必须小于或等于：1但为 [49 ]. 这个限制可以通过改变[index.max_ngram_diff] 索引级别设置来设置。"}],"type":"illegal_argument_exception","re​​ason":"NGram Tokenizer 中 max_gram 和 min_gram 之间的差异必须小于或等于：1但为 [49]。可以通过更改 [index.max_ngram_diff] 索引级别设置来设置此限制。"},"status":400}

基本上，默认情况下，NGram Tokenizer 中 max_gram 和 min_gram 之间的差异不能超过 1，如果您想更改它，那么在您的索引设置中，您需要通过添加以下设置来更改它。

"max_ngram_diff" : "50" --> you can mention this number accoding to your requirement.

下面是我的索引设置，在这里你可以看到我有一个区别47，我max_gram并min_gram因此设置max_ngram_diff到50。

{ 
    "settings": {
        "index": {
            "analysis": {
                "analyzer": {
                    "prefix": {
                        "type": "custom",
                        "filter": [
                            "lowercaseFilter"
                        ],
                        "tokenizer": "edgeNGramTokenizer"
                    }
                },
                "tokenizer": {
                    "edgeNGramTokenizer": {
                        "token_chars": [
                            "letter",
                            "digit"
                        ],
                        "min_gram": "1",
                        "type": "edgeNGram",
                        "max_gram": "40"
                    },
                    "loginNGram": {
                        "type": "nGram",
                        "min_gram": "3",
                        "max_gram": "50"
                    }
                }
            },
            "number_of_shards": "1",
            "number_of_replicas": "0",
            "max_ngram_diff" : "50"
        }
    }
} 

编辑：添加官方Elastic 文档，其中解释了 max_gram 的默认长度为 2，min_gram 的默认长度为 1，因此它们之间的默认差异不能超过 1，因此例外。然后从同一个文档中摘录

索引级别设置 index.max_ngram_diff 控制 max_gram 和 min_gram 之间的最大允许差异。

Answer 2

人们还可以使用索引模板将设置自动应用于所有新索引：

curl -X PUT "localhost:9200/_index_template/template_1?pretty" -H 'Content-Type: application/json' -d'
{
  "index_patterns": [
      "*"
  ],
  "template": {
    "settings": {
      "index": {
         "max_ngram_diff": 50
      }
    }
  }
}
'

删除每个索引不会删除模板，但必须手动删除：

curl -X DELETE "localhost:9200/_index_template/template_1