Advanced Usage

This section is devoted to some of the advanced uses of DQL

API

DQL execution is available as a python library. For example:

import dql

engine = dql.Engine()
engine.connect_to_region('us-west-1')
results = engine.execute("SCAN mytable LIMIT 10")
for item in results:
    print dict(item)

The return value will vary based on the type of query.

Embedded Python

DQL supports the use of python expressions anywhere that you would otherwise have to specify a data type. Just surround the python with backticks. Create your variable scope as a dict and pass it to the engine with the commands:

>>> engine.scope = {'foo1': 1, 'foo2': 2}
>>> engine.execute("INSERT INTO foobars (foo) VALUES (`foo1`), (`foo2`)")

The interactive client has a special way to modify the scope. You can switch into ‘code’ mode to execute python, and then use that scope as the engine scope:

us-west-1> code
>>> foo1 = 1
>>> import time
>>> endcode
us-west-1> INSERT INTO foobars (foo) VALUES (`foo1`), (`time.time()`)
success

You can also spread the expressions across multiple lines by using the format m`<expr>`. If you do this, you will need to return a value. The difference here is between using eval and exec in python.

us-west-1> UPDATE foobars SET foo = m`
         > if bar % 2 == 0:
         >     return bar**2
         > else:
         >     return bar - 1
         > `;
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