Why is the Google App Engine limiting GQL queries?

Question

I read about App Engine on Wikipedia and came across some GQL limitations:

• JOIN is not supported

• can SELECT no more than one table at a time

• can contain no more than 1 column in the WHERE clause

What are the benefits of these restrictions?

Are these restrictions common in other places where scalability is a priority?

Answer 1

The data warehouse that GQL is talking to:

• not a relational database like MySQL or PostgreSQL
• is a column oriented DBMS called BigTable

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GQL SQL, SQL.

:

• http://en.wikipedia.org/wiki/Column-oriented_DBMS
• http://en.wikipedia.org/wiki/BigTable
• http://code.google.com/appengine/docs/datastore/overview.html
• http://code.google.com/appengine/docs/datastore/gqlreference.html

Answer 2

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Answer 3

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: , , . GQL WHERE. , . :

http://code.google.com/appengine/docs/python/datastore/queries.html