mahara-contributors team mailing list archive

[Aaron Wells <1427885@xxxxxxxxxxxxxxxxxx>]

Another idea would be to sniff the DB, and if they're using Postgres 8.4
or later, we use a recursive query on the artefact.parent column. Which,
apparently, will probably be more performant than examining the "path"
column or using the nested set technique.
http://www.postgresql.org/docs/8.4/static/queries-with.html

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https://bugs.launchpad.net/bugs/1427885

Title:
  Change "artefact.path" column to use the "nested set" technique for
  managing hierarchical data

Status in Mahara ePortfolio:
  Triaged

Bug description:
  Originally, we just had each artefact store its parent ID. This is
  slow because it requires running multiple queries to find all the
  descendants of a node.

  Then, we added a "path" element to each artefact. This is better, but
  you can't get a performance improvement by indexing the column,
  because most of the queries rely on the "LIKE" operator. (See
  https://bugs.launchpad.net/mahara/+bug/1423700 )

  So if we want to squeeze more performance out of this, I think the one
  remaining thing to look into is the "nested set" technique. This
  technique results in very fast searches for descendants, with the cost
  of somewhat slower writes. http://mikehillyer.com/articles/managing-
  hierarchical-data-in-mysql/

  There are even existing PHP libraries for using the technique, such as
  this one: http://www.sideralis.org/baobab/

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