elasticsearch的写操作是原子性的，可以通过如下两种方式实现es写操作的乐观锁。
基于_version
==version_type在elasticsearch6.x被移除，故该方法不适用于6.x版本==，详见https://www.elastic.co/guide/en/elasticsearch/reference/6.7/docs-update.html
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| PUT /user/user_type/1
{
"name": "tom",
"age": 18,
"doc_version": 1 // 自定义的文档版本号,用于乐观锁
}
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只更新低版本的记录
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| PUT /user/user_type/1?version=2&version_type=external_gt
{
"name": "tom",
"age": 18,
"doc_version": 2
}
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忽略版本号强制更新
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| PUT /user/user_type/1?version=3&version_type=force
{
"name": "tom",
"age": 18,
"doc_version": 3
}
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基于script
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| PUT /user/user_type/1
{
"name": "tom",
"age": 18,
"doc_version": 1
}
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只更新es中doc_version版本低的记录
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| POST /user/user_type/1/_update
{
"script": {
"source": "if(params.doc_force == true || ctx._source.doc_version < params.doc_version){for(entry in params.entrySet()){if (entry.getKey() != 'ctx') ctx._source[entry.getKey()] = entry.getValue();}}else{ctx.op = 'none'}",
"lang": "painless",
"params": {
"name": "tom",
"age": 19,
"doc_version": 19
}
}
}
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忽略自定义版本号doc_version强制更新记录
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| POST /user/user_type/1/_update
{
"script": {
"source": "if(params.doc_force == true || ctx._source.doc_version < params.doc_version){for(entry in params.entrySet()){if (entry.getKey() != 'ctx') ctx._source[entry.getKey()] = entry.getValue();}}else{ctx.op = 'none'}",
"lang": "painless",
"params": {
"name": "tom",
"age": 19,
"doc_version": 19,
"doc_force": true
}
}
}
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注：读取script中的params的值时，需要过滤掉params.ctx，原因是es的painless脚本会自动向params中添加ctx，如果不过滤，则上述的更新语法会报如下错误：
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| {
"error": {
"root_cause": [
{
"type": "remote_transport_exception",
"reason": "[0l2AYvx][127.0.0.1:9300][indices:data/write/update[s]]"
}
],
"type": "illegal_argument_exception",
"reason": "Iterable object is self-referencing itself"
},
"status": 400
}
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详见https://github.com/elastic/elasticsearch/pull/32096。