couchbase Reduce 给出不需要的结果

Question

我有一个映射函数，return结果如下：

{"total_rows":100995,"rows":[
{"id":"00001_372792","key":["00001","CADENCIER",0],"value":-0.1961035657664066},
{"id":"00001_372792","key":["00001","CADENCIER",0],"value":-0.1961035657664066},
{"id":"00001_386302","key":["00001","CADENCIER",0],"value":0.6934708647727543},
{"id":"00001_386302","key":["00001","CADENCIER",0],"value":0.6934708647727543},
{"id":"00001_386963","key":["00001","CADENCIER",0],"value":0.6922628824612621},
{"id":"00001_386963","key":["00001","CADENCIER",0],"value":0.6922628824612621},
{"id":"00001_387089","key":["00001","CADENCIER",0],"value":0.6919048724571887},
{"id":"00001_387089","key":["00001","CADENCIER",0],"value":0.6919048724571887},
{"id":"00001_387091","key":["00001","CADENCIER",0],"value":0.6919048724571887},
{"id":"00001_387091","key":["00001","CADENCIER",0],"value":0.6919048724571887},
{"id":"00001_387099","key":["00001","CADENCIER",0],"value":0.6921140124188077},
{"id":"00001_387099","key":["00001","CADENCIER",0],"value":0.6921140124188077},
{"id":"00001_387105","key":["00001","CADENCIER",0],"value":0.6921140124188077},
{"id":"00001_387105","key":["00001","CADENCIER",0],"value":0.6921140124188077},
{"id":"00001_387193","key":["00001","CADENCIER",0],"value":0.6936603115840247},
{"id":"00001_387193","key":["00001","CADENCIER",0],"value":0.6936603115840247},
{"id":"00001_387848","key":["00001","CADENCIER",1],"value":-0.29332158594360835},
{"id":"00001_387848","key":["00001","CADENCIER",1],"value":-0.29332158594360835},
{"id":"00001_388313","key":["00001","CADENCIER",1],"value":-0.0461553701861542},
{"id":"00001_388313","key":["00001","CADENCIER",1],"value":-0.0461553701861542},
{"id":"00001_388806","key":["00001","CADENCIER",1],"value":-0.04833054041013961},
{"id":"00001_388806","key":["00001","CADENCIER",1],"value":-0.04833054041013961},
{"id":"00001_388897","key":["00001","CADENCIER",1],"value":-0.25761199232338083},
{"id":"00001_388897","key":["00001","CADENCIER",1],"value":-0.25761199232338083},
{"id":"00001_435016","key":["00001","CADENCIER",1],"value":-0.037149057843773745},
{"id":"00001_435016","key":["00001","CADENCIER",1],"value":-0.037149057843773745}
...
]}

我想减少到按键分组和return每个键的值的计数以及对值的一些其他计算。

我这样做了：

function (key, values, rereduce) {

  var result = {};
  var ecartsSum;
  for(var i = 0; i < values.length; i++) {
    ecartsSum =+ values[i];
  }
  result.productsNumber = values.length;
  result.index = 100 + (Math.tan(ecartsSum/values.length)) * 100
  return result;
}

当我使用键 ["00001","CADENCIER",0]

请求视图时

我得到这个结果：

{
  "productsNumber": 3,
  "index": null
}

这完全不是我预期的结果。

PS：我将这些选项用于 select： connection_timeout=600000000&full_set=true&group=true&inclusive_end=true&key=%5B%2200001%22,%22CADENCIER%22,0%5D&limit=6&reduce=true&skip=0&stale=false

Answer 1

并非给定键的所有值都一次传递给 reduce 函数。 MapReduce 视图将处理数据的子集，减少每个子集并使用相同的 reduce 函数组合它们，直到处理完所有值。

您需要使用 rereduce 参数，以便该函数可以减少之前对其自身调用的输出。

来自 Re-reduce Argument 文档：

In order to handle incremental map/reduce functionality (i.e. updating an existing view), each function must also be able to handle and consume the functions own output. This is because in an incremental situation, the function must be handle both the new records, and previously computed reductions.

尝试类似 documentation 中的示例：

function(key, values, rereduce) {
  var result = {total: 0, count: 0};
  for(i=0; i < values.length; i++) {
    if(rereduce) {
        result.total = result.total + values[i].total;
        result.count = result.count + values[i].count;
    } else {
        result.total = sum(values);
        result.count = values.length;
    }
  }
  return(result);
}

couchbase Reduce 给出不需要的结果

couchbase Reduce gives not wanted result

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