在查询时覆盖字段值
编辑在查询时覆盖字段值编辑
如果创建一个与映射中已存在的字段同名的运行时字段，则运行时字段会覆盖映射的字段。在查询时，Elasticsearch 会评估运行时字段，根据脚本计算值，并将该值作为查询的一部分返回。由于运行时字段会覆盖映射的字段，因此您可以覆盖搜索中返回的值，而无需修改映射的字段。
例如，假设您将以下文档索引到 my-index-000001 中
response = client.bulk(
index: 'my-index-000001',
refresh: true,
body: [
{
index: {}
},
{
"@timestamp": 1_516_729_294_000,
model_number: 'QVKC92Q',
measures: {
voltage: 5.2
}
},
{
index: {}
},
{
"@timestamp": 1_516_642_894_000,
model_number: 'QVKC92Q',
measures: {
voltage: 5.8
}
},
{
index: {}
},
{
"@timestamp": 1_516_556_494_000,
model_number: 'QVKC92Q',
measures: {
voltage: 5.1
}
},
{
index: {}
},
{
"@timestamp": 1_516_470_094_000,
model_number: 'QVKC92Q',
measures: {
voltage: 5.6
}
},
{
index: {}
},
{
"@timestamp": 1_516_383_694_000,
model_number: 'HG537PU',
measures: {
voltage: 4.2
}
},
{
index: {}
},
{
"@timestamp": 1_516_297_294_000,
model_number: 'HG537PU',
measures: {
voltage: 4
}
}
]
)
puts response
POST my-index-000001/_bulk?refresh=true
{"index":{}}
{"@timestamp":1516729294000,"model_number":"QVKC92Q","measures":{"voltage":5.2}}
{"index":{}}
{"@timestamp":1516642894000,"model_number":"QVKC92Q","measures":{"voltage":5.8}}
{"index":{}}
{"@timestamp":1516556494000,"model_number":"QVKC92Q","measures":{"voltage":5.1}}
{"index":{}}
{"@timestamp":1516470094000,"model_number":"QVKC92Q","measures":{"voltage":5.6}}
{"index":{}}
{"@timestamp":1516383694000,"model_number":"HG537PU","measures":{"voltage":4.2}}
{"index":{}}
{"@timestamp":1516297294000,"model_number":"HG537PU","measures":{"voltage":4.0}}
您稍后意识到 HG537PU 传感器没有报告其真实电压。索引值应该比报告值高 1.7 倍！您无需重新索引数据，而可以在 _search 请求的 runtime_mappings 部分中定义一个脚本来覆盖 voltage 字段，并在查询时计算新值。
如果您搜索型号与 HG537PU 匹配的文档
response = client.search(
index: 'my-index-000001',
body: {
query: {
match: {
model_number: 'HG537PU'
}
}
}
)
puts response
GET my-index-000001/_search
{
"query": {
"match": {
"model_number": "HG537PU"
}
}
}
响应包括与型号 HG537PU 匹配的文档的索引值
{
...
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : 1.0296195,
"hits" : [
{
"_index" : "my-index-000001",
"_id" : "F1BeSXYBg_szTodcYCmk",
"_score" : 1.0296195,
"_source" : {
"@timestamp" : 1516383694000,
"model_number" : "HG537PU",
"measures" : {
"voltage" : 4.2
}
}
},
{
"_index" : "my-index-000001",
"_id" : "l02aSXYBkpNf6QRDO62Q",
"_score" : 1.0296195,
"_source" : {
"@timestamp" : 1516297294000,
"model_number" : "HG537PU",
"measures" : {
"voltage" : 4.0
}
}
}
]
}
}
以下请求定义了一个运行时字段，其中脚本评估值为 HG537PU 的 model_number 字段。对于每个匹配项，脚本将 voltage 字段的值乘以 1.7。
使用 fields 参数在 _search API 上，您可以检索脚本为与搜索请求匹配的文档的 measures.voltage 字段计算的值
response = client.search(
index: 'my-index-000001',
body: {
runtime_mappings: {
'measures.voltage' => {
type: 'double',
script: {
source: "if (doc['model_number.keyword'].value.equals('HG537PU'))\n {emit(1.7 * params._source['measures']['voltage']);}\n else{emit(params._source['measures']['voltage']);}"
}
}
},
query: {
match: {
model_number: 'HG537PU'
}
},
fields: [
'measures.voltage'
]
}
)
puts response
POST my-index-000001/_search
{
"runtime_mappings": {
"measures.voltage": {
"type": "double",
"script": {
"source":
"""if (doc['model_number.keyword'].value.equals('HG537PU'))
{emit(1.7 * params._source['measures']['voltage']);}
else{emit(params._source['measures']['voltage']);}"""
}
}
},
"query": {
"match": {
"model_number": "HG537PU"
}
},
"fields": ["measures.voltage"]
}
查看响应，每个结果的 measures.voltage 计算值为 7.14 和 6.8。这看起来更合理了！运行时字段在搜索请求中计算此值，而无需修改映射的值，该值仍在响应中返回
{
...
"hits" : {
"total" : {
"value" : 2,
"relation" : "eq"
},
"max_score" : 1.0296195,
"hits" : [
{
"_index" : "my-index-000001",
"_id" : "F1BeSXYBg_szTodcYCmk",
"_score" : 1.0296195,
"_source" : {
"@timestamp" : 1516383694000,
"model_number" : "HG537PU",
"measures" : {
"voltage" : 4.2
}
},
"fields" : {
"measures.voltage" : [
7.14
]
}
},
{
"_index" : "my-index-000001",
"_id" : "l02aSXYBkpNf6QRDO62Q",
"_score" : 1.0296195,
"_source" : {
"@timestamp" : 1516297294000,
"model_number" : "HG537PU",
"measures" : {
"voltage" : 4.0
}
},
"fields" : {
"measures.voltage" : [
6.8
]
}
}
]
}
}