问题描述
REQUIREMENT :按照加入日期 (/Employee/JoiningDate) 的升序获取与查询匹配的员工 ID (/Employee/@id) ) 尽快
环境:MarkLogic DB 拥有100 万 个员工 XML
QUERY-1 [运行速度很慢,但按正确顺序返回数据]
let $fullQuery :=
cts:and-query((
cts:directory-query("/employee/","infinity"),cts:element-value-query(fn:QName("","DeptName"),"Sales",("case-insensitive")),"SubDeptName"),"Micro",("case-insensitive"))
))
let $queryOptions := ("unfiltered",cts:index-order(cts:element-reference(fn:QName("","JoiningDate"),("type=dateTime")),"ascending"))
return cts:search(/Employee,$fullQuery,$queryOptions)!fn:string(./@id) (: Using ! to get id's in sorted order. This seems to affect performance quite heavily. :)
QUERY-2 [运行速度非常快,但返回的数据顺序不正确]
let $fullQuery :=
cts:and-query((
cts:directory-query("/employee/",("case-insensitive"))
))
let $queryOptions := ("concurrent")
return cts:element-attribute-values(xs:QName("Employee"),xs:QName("id"),(),$queryOptions,$fullQuery)
如何使用上述两种方法之一来满足要求?
解决方法
cts:value-co-occurrences
将让您按一个索引排序,同时从另一个索引返回值。
例如
for $v in cts:value-co-occurrences(
cts:element-reference(xs:QName("JoiningDate"),cts:element-attribute-reference(xs:QName("Employee"),xs:QName("id")),(),$fullQuery
)
return $v/cts:value[2]/string(.)