我有一个 BaseX XML 数据库，只有一个小的 XML 文件。这些文件基本上由两种结构组成。一是PlatformCategory有 46 个实例，另一个PlatformGenericType有 213 个实例。
PlatformGenericType有参考PlatformCategory in the href属性。
<PlatformGeneralType id="/plib/platformgeneraltypes/pgt1">
<name>No statement</name>
<enum>NO_STATEMENT</enum>
<isOfPlatformCategory href="/plib/platformcategories/pc1"/>
<readOnly>true</readOnly>
</PlatformGeneralType>
<PlatformCategory id="/plib/platformcategories/pc1">
<name>No statement</name>
<enum>NO_STATEMENT</enum>
<environment>AIR</environment>
<readOnly>true</readOnly>
</PlatformCategory>
当我执行以下查询时，大约需要六秒钟才能获得结果：
//PlatformGeneralType[isOfPlatformCategory/@href=//PlatformCategory[environment="AIR"]/@id]
我可以做什么来优化这个查询？
请注意，我运行了“优化全部”。
Update: 上一个查询的问题似乎已经解决了。但是当我使用以下扩展查询时，查询需要 44,28 秒：
/PLib/PlatformSpecificTypes/PlatformSpecificType
[isOfPlatformGeneralType/@href=/PLib/PlatformGeneralTypes/PlatformGeneralType
[isOfPlatformCategory/@href=/PLib/PlatformCategories/PlatformCategory
[environment='AIR']/@id]/@id]
共有 8939 个实例PlatformSpecificType及其结构：
<PlatformSpecificTypes>
<PlatformSpecificType id="/plib/platformspecifictypes/DataShip.3">
<name>Meko 360H2</name>
<lethalityLevel>LOW</lethalityLevel>
<isOfPlatformGeneralType href="/plib/platformgeneraltypes/pgt62"/>
<ownedByCountry href="/plib/countries/10"/>
</PlatformSpecificType>
</PlatformSpecificTypes>
其查询信息：
询问：
/PLib/PlatformSpecificTypes/PlatformSpecificType[isOfPlatformGeneralType/@href=/PLib/PlatformGeneralTypes/PlatformGeneralType[isOfPlatformCategory/@href=/PLib/PlatformCategories/PlatformCategory[environment='AIR']/@id]/@id]
结果：
- 点击数：3642 件
- 更新：0 项
- 印刷版：2048 KB
- 读锁定：本地[command_plib]
- 写锁定：无
定时：
- 解析：1.25 毫秒
- 编译：0.71 毫秒
- 评估：44248.94 毫秒
- 打印：37.11 毫秒
- 总时间：44288.02 毫秒
查询计划：
数据库属性：
Database Properties
Name: command_plib
Size: 20247 KB
Nodes: 781606
Documents: 1
Binaries: 0
Timestamp: 2015-06-12-10-12-14
Resource Properties
Input Path: /home/sceran/Documents/PLIB/command_plib.xml
Input Size: 21354 KB
Timestamp: 2015-06-11-15-34-07
Encoding: UTF-8
CHOP: true
Indexes
Up-to-date: true
TEXTINDEX: true
ATTRINDEX: true
FTINDEX: false
LANGUAGE: English
STEMMING: true
CASESENS: true
DIACRITICS: false
STOPWORDS:
UPDINDEX: false
AUTOOPTIMIZE: false
MAXCATS: 100
MAXLEN: 96
查询信息：
Compiling:
- rewriting descendant-or-self step(s)
- rewriting descendant-or-self step(s)
- converting descendant::*:PlatformGeneralType[(*:isOfPlatformCategory/@*:href = root()/descendant::*:PlatformCategory[(*:environment = "AIR")]/@*:id)] to child steps
Query:
//PlatformGeneralType[isOfPlatformCategory/@href=//PlatformCategory[environment="AIR"]/@id]
Optimized Query:
db:open-pre("command_plib",0)/*:PLib/*:PlatformGeneralTypes/*:PlatformGeneralType[(*:isOfPlatformCategory/@*:href = root()/descendant::*:PlatformCategory[(*:environment = "AIR")]/@*:id)]
Result:
- Hit(s): 55 Items
- Updated: 0 Items
- Printed: 12776 Bytes
- Read Locking: local [command_plib]
- Write Locking: none
Timing:
- Parsing: 0.55 ms
- Compiling: 0.3 ms
- Evaluating: 5786.29 ms
- Printing: 1.0 ms
- Total Time: 5788.15 ms
Query plan:
<QueryPlan compiled="true">
<IterPath>
<DBNode name="command_plib" pre="0"/>
<IterStep axis="child" test="*:PLib"/>
<IterStep axis="child" test="*:PlatformGeneralTypes"/>
<IterStep axis="child" test="*:PlatformGeneralType">
<CmpG op="=">
<CachedPath>
<IterStep axis="child" test="*:isOfPlatformCategory"/>
<IterStep axis="attribute" test="*:href"/>
</CachedPath>
<IterPath>
<Root/>
<IterStep axis="descendant" test="*:PlatformCategory">
<CmpG op="=">
<CachedPath>
<IterStep axis="child" test="*:environment"/>
</CachedPath>
<Str value="AIR" type="xs:string"/>
</CmpG>
</IterStep>
<IterStep axis="attribute" test="*:id"/>
</IterPath>
</CmpG>
</IterStep>
</IterPath>
</QueryPlan>
更新二：我怀疑 PlatformSpecificTypes 的结构会阻止索引。我想知道如果我按如下方式更改它，会提高查询性能吗？
<PlatformSpecificTypes>
<PlatformSpecificType id="/plib/platformspecifictypes/DataShip.3">
<name>Meko 360H2</name>
<lethalityLevel>LOW</lethalityLevel>
**<isOfPlatformGeneralType>/plib/platformgeneraltypes/pgt62 </isOfPlatformGeneralType>**
<ownedByCountry href="/plib/countries/10"/>
</PlatformSpecificType>
</PlatformSpecificTypes>
更新三：我已经上传了XML 文件要点 https://gist.github.com/anonymous/821b74d26e631a07f212，以便您可以检查它。
现在，当我执行以下查询时，我需要大约 28 秒才能获得结果。
/root/PlSpTys/PlSpTy[isOfPlGeTy/@href=/root/PlGeTys/PlGeTy[isOfPlCt/@href=/root/PlCts/PlCt[environment='AIR']/@id]/@id]
以下是查询信息：
Query:
/root/PlSpTys/PlSpTy[isOfPlGeTy/@href=/root/PlGeTys/PlGeTy[isOfPlCt/@href=/root/PlCts/PlCt[environment='AIR']/@id]/@id]
Result:
- Hit(s): 3642 Items
- Updated: 0 Items
- Printed: 257 KB
- Read Locking: local [Output6]
- Write Locking: none
Timing:
- Parsing: 0.66 ms
- Compiling: 0.34 ms
- Evaluating: 28398.32 ms
- Printing: 4.63 ms
- Total Time: 28403.97 ms
Query plan:
<QueryPlan compiled="true">
<IterPath>
<DBNode name="Output6" pre="0"/>
<IterStep axis="child" test="*:root"/>
<IterStep axis="child" test="*:PlSpTys"/>
<IterStep axis="child" test="*:PlSpTy">
<CmpG op="=">
<CachedPath>
<IterStep axis="child" test="*:isOfPlGeTy"/>
<IterStep axis="attribute" test="*:href"/>
</CachedPath>
<IterPath>
<Root/>
<IterStep axis="child" test="*:root"/>
<IterStep axis="child" test="*:PlGeTys"/>
<IterStep axis="child" test="*:PlGeTy">
<CmpG op="=">
<CachedPath>
<IterStep axis="child" test="*:isOfPlCt"/>
<IterStep axis="attribute" test="*:href"/>
</CachedPath>
<IterPath>
<Root/>
<IterStep axis="child" test="*:root"/>
<IterStep axis="child" test="*:PlCts"/>
<IterStep axis="child" test="*:PlCt">
<CmpG op="=">
<CachedPath>
<IterStep axis="child" test="*:environment"/>
</CachedPath>
<Str value="AIR" type="xs:string"/>
</CmpG>
</IterStep>
<IterStep axis="attribute" test="*:id"/>
</IterPath>
</CmpG>
</IterStep>
<IterStep axis="attribute" test="*:id"/>
</IterPath>
</CmpG>
</IterStep>
</IterPath>
</QueryPlan>
您能帮我优化查询持续时间吗？
