Solr的学习使用之（七）Solr高级查询facet、facet.pivot简介

以下转载自：http://hongweiyi.com/2013/03/apache-solr-facet-introduction/

1、什么是Faceted Search

Facet['fæsɪt]很难翻译，只能靠例子来理解了。Solr作者Yonik Seeley也给出更为直接的名字：导航（Guided Navigation）、参数化查询（Paramatic Search）。

上面是比较直接的Faceted Search例子，品牌、产品特征、卖家，均是Facet。而Apple、Lenovo等品牌，就是Facet values或者说Constraints，而Facet values所带的统计值就是Facet count/Constraint count。

2、Facet使用

q = 超级本
facet = true
facet.field = 产品特性
facet.field = 品牌
facet.field = 卖家

http://…/select?q=超级本&facet=true&wt=json

&facet.field=品牌&facet.field=产品特性&facet.field=卖家

也可以提交查询条件，设置fq(filter query)。

q = 电脑
facet = true
fq = 价格:[8000 TO *]
facet.mincount = 1 // fq将不符合的字段过滤后，会显示count为0
facet.field = 产品特性
facet.field = 品牌
facet.field = 卖家

http://…/select?q=超级本&facet=true&wt=json

&fq=价格:[8000 TO *]&facet.mincount=1

&facet.field=品牌&facet.field=产品特性&facet.field=卖家

"facet_counts": {
"facet_fields": {
  "品牌": [
    "Apple", 4,
    "Lenovo", 39
      …]
  "产品特性": [
    "显卡", 42,
    "酷睿", 38
      …]
 
  …}}

如果用户选择了Apple这个分类，查询条件中需要添加另外一个fq查询条件，并移除Apple所在的facet.field。

http://…/select?q=超级本&facet=true&wt=json

&fq=价格:[8000 TO *]&fq=品牌:Apple&facet.mincount=1

~~&facet.field=~~品牌&facet.field=产品特性&facet.field=卖家

3、Facet参数

facet.prefix – 限制constaints的前缀

facet.mincount=0 – 限制constants count的最小返回值，默认为0

facet.sort=count – 排序的方式，根据count或者index

facet.offset=0 – 表示在当前排序情况下的偏移，可以做分页

facet.limit=100 – constraints返回的数目

facet.missing=false – 是否返回没有值的field

facet.date – Deprecated, use facet.range

facet.query

指定一个查询字符串作为Facet Constraint

facet.query = rank:[* TO 20]

facet.query = rank:[21 TO *]

 

"facet_counts": {
"facet_fields": {
  "品牌": [
    "Apple", 4,
    "Lenovo", 10
      …]
  "产品特性": [
    "显卡", 11,
    "酷睿", 20
      …]
 
  …}}

facet.range

http://…/select?&facet=true

&facet.range=price

&facet.range.start=5000

&facet.range.end=8000

&facet.range.gap=1000

 <result numFound="27" ... />
 ...
 <lst name="facet_counts">
 <lst name="facet_queries">
   <int name="rank:[* TO 20]">2</int>
   <int name="rank:[21 TO *]">15</int>
 </lst>
... 
 

WARNING: range范围是左闭右开，[start, end)

facet.pivot

这个是Solr 4.0的新特性，pivot和facet一样难理解，还是用例子来讲吧。

Syntax: facet.pivot=field1,field2,field3...

e.g. facet.pivot=comment_user, grade

	#docs	#docs grade:好	#docs 等级:中	#docs 等级:差
comment_user:1	10	8	1	1
comment_user:2	20	18	2	0
comment_user:3	15	12	2	1
comment_user:4	18	15	2	1

"facet_counts":{
"facet_pivot":{
 "comment_user, grade ":[{
   "field":"comment_user",
   "value":"1",
   "count":10,
   "pivot":[{
     "field":"grade",
     "value":"好",
     "count":8}, {
     "field":"grade",
     "value":"中",
     "count":1}, {
     "field":"grade",
     "value":"差",
     "count":1}]
   }, {
     "field":" comment_user ",
     "value":"2",
     "count":20,
     "pivot":[{
      …

没有pivot机制的话，要做到上面那点可能需要多次查询：

http://...q=comment&fq=grade:好&facet=true&facet.field=comment_user

http://...q=comment&fq=grade:中&facet=true&facet.field=comment_user

http://...q=comment&fq=grade:差&facet=true&facet.field=comment_user

Facet.pivot - Computes a Matrix of Constraint Counts across multiple Facet Fields. by Yonik Seeley.

上面那个解释很不错，只能理解不能翻译。