"ignore_above": 256,

"ignore_above": 256是在创建mapping时指定的一个参数，用于设置在索引或存储时忽略超过指定字符长度的字符串。具体来说，在上述的例子中，当创建ali_test索引时，"url"字段的类型为"keyword"，并且设置了"ignore_above": 256，意味着超过256个字符的字符串将不会被索引或存储。这样可以控制索引的大小和性能。\[2\]\[3\]
#### 引用[.reference_title]
- *1* *3* [深究｜Elasticsearch单字段支持的最大字符数?](https://blog.csdn.net/wojiushiwo987/article/details/78207980)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^insertT0,239^v3^insert_chatgpt"}} ] [.reference_item]
- *2* [【elasticsearch7】(4) 使用 ignore_above 限制字符串长度](https://blog.csdn.net/Mrerlou/article/details/118488164)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^insertT0,239^v3^insert_chatgpt"}} ] [.reference_item]
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