1. 问题引入
我们项目中有一个需求：ElasticSearch存在很多历史数据，然后需求中索引新增了一个字段，我们需要根据条件查询出历史数据，但历史数据中这个新增的字段并不存在，如何查询到历史数据呢？
1. 索引2个文档
PUT /user/_doc/1
{
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests": [ "sports", "music" ]
}
PUT /user/_doc/2
{
"first_name" : "zhangsan",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests": [ "sports", "music" ]
}
2. 给索引增加新的字段
PUT /user/_mapping
{
"properties": {
"height": {
"type": "long"
}
}
}
3. 再次索引1个文档
这个文档新增了height字段的值
PUT /user/_doc/3
{
"first_name" : "lisi",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests": [ "sports", "music" ],
"height":175
}
4. 查看索引中的文档
GET /user/_search
{
"took" : 817,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 3,
"relation" : "eq"
},
"max_score" : 1.0,
"hits" : [
{
"_index" : "user",
"_type" : "_doc",
"_id" : "1",
"_score" : 1.0,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "user",
"_type" : "_doc",
"_id" : "2",
"_score" : 1.0,
"_source" : {
"first_name" : "zhangsan",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "user",
"_type" : "_doc",
"_id" : "3",
"_score" : 1.0,
"_source" : {
"first_name" : "lisi",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests" : [
"sports",
"music"
],
"height" : 175
}
}
]
}
}
从上面的结果可以看出，在ElasticSearch中为已有索引增加一个新字段以后，老的数据并不会自动就拥有了这个新字段，也就不可能给他一个默认值。因此前面2条数据都没有 height 这个字段。
在ElasticSearch中，如果一个字段不存在或者这个字段的值为null，在检索的时候该字段会被忽略，因此也就无法做空值搜索。
PUT my_index/my_type/1
{
"first_name": "zhangsan"
}
PUT my_index/my_type/2
{
"first_name": "wangwu",
"height": null
}
例如上面的2个文档，都无法根据 height 这个字段检索。那么我们如何查询到没增加字段之前的历史数据呢？
2. must_not & exist
POST /user/_search
{
"query": {
"bool": {
"must_not": [
{
"exists": {
"field" : "height"
}
}
]
}
}
}
{
"took" : 7,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : 0.0,
"hits" : [
{
"_index" : "user",
"_type" : "_doc",
"_id" : "1",
"_score" : 0.0,
"_source" : {
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests" : [
"sports",
"music"
]
}
},
{
"_index" : "user",
"_type" : "_doc",
"_id" : "2",
"_score" : 0.0,
"_source" : {
"first_name" : "zhangsan",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests" : [
"sports",
"music"
]
}
}
]
}
}
exists 返回在原始字段中至少有一个非空值的文档：
GET /user/_search
{
"query": {
"exists" : { "field" : "height" }
}
}
{
"took" : 1,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 1,
"relation" : "eq"
},
"max_score" : 1.0,
"hits" : [
{
"_index" : "user",
"_type" : "_doc",
"_id" : "3",
"_score" : 1.0,
"_source" : {
"first_name" : "lisi",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests" : [
"sports",
"music"
],
"height" : 175
}
}
]
}
}
3. 给历史数据赋初值
对现有索引新增字段时并不会影响历史数据，因此我们可以修改历史数据文档，对历史数据设置默认值，然后根据默认值检索。
使用脚本批量更新文档：_update_by_query，如果字段的值为null，则给该字段赋初值为0
POST /user/_update_by_query
{
"script": {
"lang": "painless",
"inline": "if (ctx._source.height== null) {ctx._source.height=0}"
}
}
再次查看索引的文档：文章来源：https://www.toymoban.com/news/detail-495663.html
{
"took" : 1,
"timed_out" : false,
"_shards" : {
"total" : 1,
"successful" : 1,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : {
"value" : 3,
"relation" : "eq"
},
"max_score" : 1.0,
"hits" : [
{
"_index" : "user",
"_type" : "_doc",
"_id" : "1",
"_score" : 1.0,
"_source" : {
"about" : "I love to go rock climbing",
"last_name" : "Smith",
"interests" : [
"sports",
"music"
],
"first_name" : "John",
"age" : 25,
"height" : 0
}
},
{
"_index" : "user",
"_type" : "_doc",
"_id" : "2",
"_score" : 1.0,
"_source" : {
"about" : "I love to go rock climbing",
"last_name" : "Smith",
"interests" : [
"sports",
"music"
],
"first_name" : "zhangsan",
"age" : 25,
"height" : 0
}
},
{
"_index" : "user",
"_type" : "_doc",
"_id" : "3",
"_score" : 1.0,
"_source" : {
"about" : "I love to go rock climbing",
"last_name" : "Smith",
"interests" : [
"sports",
"music"
],
"first_name" : "lisi",
"age" : 25,
"height" : 175
}
}
]
}
}
历史数据中 height 字段都有了默认值 0文章来源地址https://www.toymoban.com/news/detail-495663.html
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