CODEWITHSUNDEEP
xquerybasex
Matthias Wuttke
Matthias Wuttke

Reputation: 2032

BaseX: Slow XQuery

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.

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.

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.

What can I do to optimize this query?

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

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: This is the query execution plan:

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>

Upvotes: 0

Views: 810

Answers (1)

Christian Gr&#252;n
Christian Gr&#252;n

Reputation: 6229

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

/ARTICLE/ART[PRDNO = "12345"]

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

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

Upvotes: 4

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