BaseX:慢速 XQuery [英] BaseX: Slow XQuery

问题描述

我有一个包含大约 20 个 XML 文件的 BaseX XML 数据库.这些文件的大小和结构各不相同.最大的文件有 524 MB.它由一个带有 267685 个 ART 子标签的父 ARTICLE 标签组成.

I've got a BaseX XML database with ~20 XML files. These files are different in size and structure. The biggest file has got 524 MB. It consists of a parent ARTICLE tag with 267685 ART subtags.

这是我的 XQuery:/ARTICLE/ART[PRDNO=12345]"(非常简单；为清楚起见省略了正确的名称空间).PRDNO 是 PRODUCT/PRD XML 结构的外键，每篇文章有多个(平均约 10 个)产品.

This is my XQuery: "/ARTICLE/ART[PRDNO=12345]" (pretty straightforward; proper namespaces omitted for clarity). PRDNO is a foreign key to the PRODUCT/PRD XML structure, there are multiple (in average ~10) products per article.

一切正常，但是这个查询很慢 - 执行大约需要 1 秒.对数据库中其他对象(数据量较小)的类似查询要快得多.

Everything works as it is supposed to, but this query is quite slow - it takes approximately 1s to execute. Similar queries for other objects in the database (where the data amount is smaller) are much faster.

我可以做些什么来优化此查询?

What can I do to optimize this query?

我运行了优化"(花了几分钟)，我确保 TEXT 索引到位.

I ran "optimize" (which took some minutes), I ensured the TEXT index is in place.

这是信息数据库"的输出:

This is the output of "info database":

> info database
Database Properties
 Name: hospindex
 Size: 1740 MB
 Nodes: 69360063
 Documents: 22
 Binaries: 0
 Timestamp: 2014-09-03-09-34-07

Resource Properties
 Timestamp: 2014-09-03-09-21-14
 Encoding: UTF-8
 CHOP: true

Indexes
 Up-to-date: true
 TEXTINDEX: true
 ATTRINDEX: true
 FTINDEX: false
 LANGUAGE: English
 STEMMING: false
 CASESENS: false
 DIACRITICS: false
 STOPWORDS:
 UPDINDEX: false
 MAXCATS: 100
 MAXLEN: 96

EDIT:这是查询执行计划:

Compiling:
- adding text() step
Query:
/*:ARTICLE/*:ART[*:PRDNO=1005935]
Optimized Query:
(db:open-pre("hospindex",0), db:open-pre("hospindex",32884731), ...)/*:ARTICLE/*:ART[(*:PRDNO/text() = 1005935)]
Result:
- Hit(s): 1 Item
- Updated: 0 Items
- Printed: 2078 Bytes
- Read Locking: local [hospindex]
- Write Locking: none
Timing:
- Parsing: 1.12 ms
- Compiling: 0.46 ms
- Evaluating: 1684.35 ms
- Printing: 0.35 ms
- Total Time: 1686.3 ms
Query plan:
<QueryPlan>
  <IterPath>
    <DBNodeSeq size="22">
      <DBNode name="hospindex" pre="0"/>
      <DBNode name="hospindex" pre="32884731"/>
      <DBNode name="hospindex" pre="33685448"/>
      <DBNode name="hospindex" pre="38260847"/>
      <DBNode name="hospindex" pre="38358876"/>
    </DBNodeSeq>
    <IterStep axis="child" test="*:ARTICLE"/>
    <IterStep axis="child" test="*:ART">
      <CmpG op="=">
        <CachedPath>
          <IterStep axis="child" test="*:PRDNO"/>
          <IterStep axis="child" test="text()"/>
        </CachedPath>
        <Int value="1005935" type="xs:integer"/>
      </CmpG>
    </IterStep>
  </IterPath>
</QueryPlan>

推荐答案

在搜索值周围使用引号时，您的查询的评估速度会快得多:

Your query will be evaluated much faster when using quotes around your search value:

/ARTICLE/ART[PRDNO = "12345"]

原因是当前版本的 BaseX 没有提供数值索引(可能包含在 BaseX 8.0 中).

The reason is that the current version of BaseX does not provide a numeric value index (it may be included in BaseX 8.0).

通过打开 QUERYINFO 选项，您可以更深入地了解查询编译步骤.

You get more insight into the query compilation steps by turning on the QUERYINFO option.

这篇关于BaseX:慢速 XQuery的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！