ECHO

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ECHO
Optimizing Queries/ Best Practices for Client
Developers Nathan Pollack January 23, 2007
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Agenda

• General best practices for running faster
  queries
• Efficient Spatial Queries
• Notes About Queries
• Query/Present Performance

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Best practices for running faster queries

• Limit end user choices, lead them down a path
  rather than open everything
• Search for collections first and limit the
  collection search by data center, spatially,
  temporal
• Compare your search to Google or Amazon you
  would not run a search on them for everything
  they have either

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Efficient Spatial Queries

• If you are querying a single data provider, name
  the data provider in the query
• If you are querying a single Collection, include
  the name of the Collection in the query as well
• Smaller spatial regions query faster
• Spatial regions with fewer points query faster
• Spatial queries are CPU-intensive

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Notes About Queries

• Queries that return large result sets take a long
  time to finish
• Use limit on number of items returned
• Use HITS and not RESULTS when querying
• Use TupleType to return only the necessary
  attributes when presenting data ECHO defaults
  to all attributes
• Return only what the user will see in the first
  present
• Prefetch the next page of results while the user
  is examining the current page

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More Notes on Queries

• Consider caching the results locally
• Remember that you can use GetMetadata to do a
  present without having to query first
• Allow user to drill down on summary granule
  information to get full record resulting in a
  present of a single granules full metadata
  record
• The goal is to move the least amount of data
  necessary to give the user a smooth experience
• Presents are relatively low load on the system