elasticsearch - 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 Ruby on Rails 应用程序，但在 Elasticsearch 上给出了关于 max_gram 和 min_gram 之间差异的错误，我没有任何 Elasticsearch 经验，所以我完全迷失在这里，我需要一些指导来执行此操作并了解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，所以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配置所有内容在 elasticsearch.yml 上，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，默认模板上也没有这个设置

Answer 1

我遇到过类似的问题，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","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}

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，如果您想要更改它，那么您需要在索引设置中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，您可以在其中看到我的 max_gram 和 min_gram 有 47 的差异，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 official Elastic 文档，解释了 max_gram 的默认长度为 2，min_gram 为 1，因此它们之间的默认差异不能超过 1，因此异常(exception)。然后来自同一文档的片段

The index level setting index.max_ngram_diff controls the maximum allowed difference between max_gram and min_gram.