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731Re: [xml-dbms] Re: UPDATE & DELETE

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  • Ronald Bourret
    Mar 2, 2001
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      Robin Fried wrote:
      >
      > Concerning the "Generate" capability, how will XML-DMBS behave if the
      > XMLDBMSKEY.HighKey is defined as a 64bit entity (e.g., bigint in SQL
      > Server)? In other words, does the underlying key grabber code in java
      > assume it's a 32bit int or a long int (64bits)?

      The code uses an int (32 bits). Assuming the JDBC driver does the
      conversion correctly (the code calls ResultSet.getInt()), it looks like
      the code should work. However, I haven't actually tried it.

      > If the latter, then it
      > should just work automatically. Looks like the code assume integer. The
      > problem is that all tables are sharing the same key generator, which
      > distributes the set of all possible keys across the entire database -- not
      > very scalable!

      Is your worry about scalability due to multiple concurrent hits on the
      XMLDBMSKey table or on running out of key values? The former shouldn't
      be a problem, since each hit on the table can be used to generate 256
      key values. If it is the latter, you are correct, since the theoretical
      limit of key values is about 4 billion and the practical limit is much
      smaller -- somewhere around 16-100 million, depending on the XML
      documents you insert.

      There are two solutions here. First, you can write your own key
      generation routine (implement the KeyGenerator interface) and pass it to
      DOMToDBMS. Second, I've considered modifying the map document so you can
      specify a different key generator for each table. However, I can't
      remember anybody ever asking for the latter, so it is very low priority.

      -- Ron
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