solr 分組order by numFound

solr控制數據的返回的排序只能使用已有的字段（字段必須索引）。

使用facet只能返回分組的次數，如：

{
  "responseHeader":{
    "status":0,
    "QTime":9,
    "params":{
      "q":"post_content:\"nike\"",
      "facet.field":"uid",
      "indent":"on",
      "rows":"0",
      "facet":"on",
      "wt":"json",
      "_":"1567574307269"}},
  "response":{"numFound":33679,"start":0,"docs":[]
  },
  "facet_counts":{
    "facet_queries":{},
    "facet_fields":{
      "uid":[
        "56616",2272,
        "59212",1393,
        "71466",1289,
        "820",1060,
        "58190",693,
        "344",675,
        "58559",524,
        "95849",439,
        "97810",412,
        "56635",405,
        "70449",356,
        "61959",269,
        "63930",250,
        "57823",245,
        "60380",238,
        "84618",235,
        "102601",225]},
    "facet_ranges":{},
    "facet_intervals":{},
    "facet_heatmaps":{}}}

使用group可以返回數據，但是不能以numFound排序，如：

{
  "responseHeader":{
    "status":0,
    "QTime":54,
    "params":{
      "q":"post_content:\"nike\"",
      "indent":"on",
      "fl":"id,post_time",
      "group.limit":"3",
      "group.ngroups":"true",
      "rows":"3",
      "wt":"json",
      "group.field":"uid",
      "_":"1567574501345",
      "group":"true"}},
  "grouped":{
    "uid":{
      "matches":33679,
      "ngroups":5238,
      "groups":[{
          "groupValue":"412",
          "doclist":{"numFound":5,"start":0,"docs":[
              {
                "id":"15874598",
                "post_time":"20190226"},
              {
                "id":"21279196",
                "post_time":"20190712"},
              {
                "id":"19830647",
                "post_time":"20190606"}]
          }},
        {
          "groupValue":"70134",
          "doclist":{"numFound":10,"start":0,"docs":[
              {
                "id":"17550386",
                "post_time":"20190418"},
              {
                "id":"17678823",
                "post_time":"20190422"},
              {
                "id":"20580963",
                "post_time":"20190624"}]
          }},
        {
          "groupValue":"89899",
          "doclist":{"numFound":92,"start":0,"docs":[
              {
                "id":"18440190",
                "post_time":"20190509"},
              {
                "id":"13451713",
                "post_time":"20181205"},
              {
                "id":"19047413",
                "post_time":"20190521"}]
          }}]}}}

如果需要以分組numFound排序返回數據，可已將將兩者結合起來。

1、先使用facet查詢提到次數最多的10個分組，如：facet.field=uid&facet.limit=10&facet=on&indent=on&q=post_content:"nike"&rows=0&wt=json

返回：

{
  "responseHeader":{
    "status":0,
    "QTime":3,
    "params":{
      "facet.limit":"10",
      "q":"post_content:\"nike\"",
      "facet.field":"uid",
      "indent":"on",
      "rows":"0",
      "facet":"on",
      "wt":"json",
      "_":"1567574501345"}},
  "response":{"numFound":33679,"start":0,"docs":[]
  },
  "facet_counts":{
    "facet_queries":{},
    "facet_fields":{
      "uid":[
        "56616",2272,
        "59212",1393,
        "71466",1289,
        "820",1060,
        "58190",693,
        "344",675,
        "58559",524,
        "95849",439,
        "97810",412,
        "56635",405]},
    "facet_ranges":{},
    "facet_intervals":{},
    "facet_heatmaps":{}}}

2、把查到的10個分組帶到group中的條件中，如：

group.field=uid&group.limit=2&group.ngroups=true&group=true&indent=on&q=post_content:"nike"%20AND%20uid:("56616","59212","71466","820","58190","344","58559","95849","97810","56635")&wt=json

返回：

{
  "responseHeader":{
    "status":0,
    "QTime":10,
    "params":{
      "q":"post_content:\"nike\" AND uid:(\"56616\",\"59212\",\"71466\",\"820\",\"58190\",\"344\",\"58559\",\"95849\",\"97810\",\"56635\")",
      "indent":"on",
      "fl":"id,uid,post_time",
      "group.limit":"2",
      "group.ngroups":"true",
      "wt":"json",
      "group.field":"uid",
      "_":"1567574501345",
      "group":"true"}},
  "grouped":{
    "uid":{
      "matches":9162,
      "ngroups":10,
      "groups":[{
          "groupValue":"95849",
          "doclist":{"numFound":439,"start":0,"docs":[
              {
                "uid":"95849",
                "id":"12472434",
                "post_time":"20181029"},
              {
                "uid":"95849",
                "id":"13150231",
                "post_time":"20181123"}]
          }},
        {
          "groupValue":"97810",
          "doclist":{"numFound":412,"start":0,"docs":[
              {
                "uid":"97810",
                "id":"17011576",
                "post_time":"20190401"},
              {
                "uid":"97810",
                "id":"20836190",
                "post_time":"20190702"}]
          }},
        {
          "groupValue":"71466",
          "doclist":{"numFound":1289,"start":0,"docs":[
              {
                "uid":"71466",
                "id":"9568951",
                "post_time":"20180711"},
              {
                "uid":"71466",
                "id":"12310677",
                "post_time":"20181023"}]
          }},
        {
          "groupValue":"344",
          "doclist":{"numFound":675,"start":0,"docs":[
              {
                "uid":"344",
                "id":"16181520",
                "post_time":"20190307"},
              {
                "uid":"344",
                "id":"337442",
                "post_time":"20151204"}]
          }},
        {
          "groupValue":"59212",
          "doclist":{"numFound":1393,"start":0,"docs":[
              {
                "uid":"59212",
                "id":"17192718",
                "post_time":"20190408"},
              {
                "uid":"59212",
                "id":"7620333",
                "post_time":"20180316"}]
          }},
        {
          "groupValue":"820",
          "doclist":{"numFound":1060,"start":0,"docs":[
              {
                "uid":"820",
                "id":"15442810",
                "post_time":"20190213"},
              {
                "uid":"820",
                "id":"10022689",
                "post_time":"20180731"}]
          }},
        {
          "groupValue":"58559",
          "doclist":{"numFound":524,"start":0,"docs":[
              {
                "uid":"58559",
                "id":"9235985",
                "post_time":"20180627"},
              {
                "uid":"58559",
                "id":"14815380",
                "post_time":"20190121"}]
          }},
        {
          "groupValue":"56635",
          "doclist":{"numFound":405,"start":0,"docs":[
              {
                "uid":"56635",
                "id":"3023676",
                "post_time":"20160415"},
              {
                "uid":"56635",
                "id":"7508607",
                "post_time":"20180309"}]
          }},
        {
          "groupValue":"58190",
          "doclist":{"numFound":693,"start":0,"docs":[
              {
                "uid":"58190",
                "id":"6323225",
                "post_time":"20171114"},
              {
                "uid":"58190",
                "id":"5452944",
                "post_time":"20170804"}]
          }},
        {
          "groupValue":"56616",
          "doclist":{"numFound":2272,"start":0,"docs":[
              {
                "uid":"56616",
                "id":"10634218",
                "post_time":"20180820"},
              {
                "uid":"56616",
                "id":"10634219",
                "post_time":"20180820"}]
          }}]}}}

使用代碼根據numFound排序（逆序）,得到正確數據。