我正在开发一个在后端使用RavenDB的应用程序.这是我第一次使用Raven,并且我在使用Map / Reduce时遇到困难.
我到过reading the doc’s,但是很遗憾,我在过程中没有取得任何进展.
基本上我有成千上万个这样的文档.
{
.....
"Severity": {
"Code": 6,
"Data": "Info"
},
"Facility": {
"Code": 16,
"Data": "Local Use 0 (local0)"
},
.....
}
而且,我需要使用如下所示的输出进行单个查询.
{"Severity": [
{"Emergency":0},
{"Alert":0},
{"Critical":0},
{"Error":0},
{"Warning":0},
{"Notice":0},
{"Info":2711},
{"Debug":410}
],
"Facility": [
{"Kernel Messages":0},
{"User-Level Messages":0},
{"Mail System":0},
{"System Daemons":0},
{"Security/Authorization Messages":0},
{"Internal Syslogd Messages":0},
{"Line Printer Subsystem":2711},
{"Network News Subsystem":410},
....
{"Local Use 0 (local0)": 2574},
...
]}
因此,严重性/便利性数组中的“键”是上述json数据的“数据”部分,而严重性/便利性数组中的“值”是每种Code类型的文档Count.
例:
以上述数据为指导,
There are 2711 documents in my database with an
Info
severity.
There are 410 documents in my database with aDebug
severity.
There are 2574 documents in my database with alocal0
facility.
etc…
我想做的是在应用启动时生成适当的索引(或检查它们是否已经存在),但是我什至不知道从哪里开始.
注意:应用程序需要生成索引,仅将索引手动写入RavenDB Web UI是不够的.
解决方法:
您将需要组合多种技术来实现此目的,但这是完全可行的.
这是一个适合您的索引.
public class MyIndex : AbstractMultiMapIndexCreationTask<MyIndex.ReduceResult>
{
public class ReduceResult
{
public string Source { get; set; }
public string Code { get; set; }
public string Data { get; set; }
public int Count { get; set; }
}
public MyIndex()
{
AddMap<MyDoc>(docs => from doc in docs
select new
{
Source = "Severity",
doc.Severity.Code,
doc.Severity.Data,
Count = 1
});
AddMap<MyDoc>(docs => from doc in docs
select new
{
Source = "Facility",
doc.Facility.Code,
doc.Facility.Data,
Count = 1
});
Reduce = results => from result in results
group result by new { result.Source, result.Code }
into g
select new
{
g.Key.Source,
g.Key.Code,
g.First().Data,
Count = g.Sum(x => x.Count)
};
TransformResults = (database, results) =>
from result in results
group result by 0
into g
select new
{
Severity = g.Where(x => x.Source == "Severity")
.ToDictionary(x => x.Data, x => x.Count),
Facility = g.Where(x => x.Source == "Facility")
.ToDictionary(x => x.Data, x => x.Count)
};
}
}
您还需要一个用于转换结果的容器类:
public class MyDocCounts
{
public IDictionary<string, int> Severity { get; set; }
public IDictionary<string, int> Facility { get; set; }
}
您可以这样查询它:
var result = session.Query<MyIndex.ReduceResult, MyIndex>()
.As<MyDocCounts>()
.ToList().First();
.ToList()似乎是多余的,但是这是必需的,因为我们在转换中进行了分组.
完整的单元测试为here.其输出如下所示:
{
"Severity": {
"AAA": 20,
"BBB": 20,
"CCC": 20,
"DDD": 20,
"EEE": 20
},
"Facility": {
"FFF": 20,
"GGG": 20,
"HHH": 20,
"III": 20,
"JJJ": 20
}
}
标签:mapreduce,ravendb,c 来源: https://codeday.me/bug/20191031/1974061.html
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