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Version: 3.1.X

Element <extract>

The <extract> element processes the current record using a Field Select Table (FST) to generate keys (terms) for the inverted file.

It requires several parameters to be set up:

  1. FST: Defined by <parm name="fst">.
  2. Destination DB: Defined by <parm name="keysdb"> (temporary database to hold keys).
  3. Internal Mappings: You must map Isis_Key and Isis_Posting to virtual tags.

Usage​

  • Allowed content: <pft>
  • Parent elements: <do>, <function>, <hl>, <loop>, <section>, <update>

Configuration​

Before calling <extract>, you must define specific fields:

  • <field action="define" tag="...">Isis_Key</field>: Holds the extracted term.
  • <field action="define" tag="...">Isis_Posting</field>: Holds the posting information (MFN, Tag, Occ, etc.).

Example​

Extracting keys from records in CDS to a temporary keysdb.

<do task="mfnrange">
   <parm name="fst">1 0 v1</parm>
   <parm name="keysdb">tmp1</parm>
   
   <field action="define" tag="1">Isis_Posting</field>
   <field action="define" tag="2">Isis_Key</field>
   
   <loop>
      <extract>this</extract>
   </loop>
</do>