path: root/boto/dynamodb/table.py

# Copyright (c) 2012 Mitch Garnaat http://garnaat.org/
# Copyright (c) 2012 Amazon.com, Inc. or its affiliates.  All Rights Reserved
#
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# copy of this software and associated documentation files (the
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# tribute, sublicense, and/or sell copies of the Software, and to permit
# persons to whom the Software is furnished to do so, subject to the fol-
# lowing conditions:
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# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABIL-
# ITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
# SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 
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from boto.dynamodb.schema import Schema
from boto.dynamodb.item import Item
from boto.dynamodb import exceptions as dynamodb_exceptions
import time

class Table(object):
    """
    An Amazon DynamoDB table.

    :ivar name: The name of the table.
    :ivar create_time: The date and time that the table was created.
    :ivar status: The current status of the table.  One of:
        'ACTIVE', 'UPDATING', 'DELETING'.
    :ivar schema: A :class:`boto.dynamodb.schema.Schema` object representing
        the schema defined for the table.
    :ivar item_count: The number of items in the table.  This value is
        set only when the Table object is created or refreshed and
        may not reflect the actual count.
    :ivar size_bytes: Total size of the specified table, in bytes.
        Amazon DynamoDB updates this value approximately every six hours.
        Recent changes might not be reflected in this value.
    :ivar read_units: The ReadCapacityUnits of the tables
        Provisioned Throughput.
    :ivar write_units: The WriteCapacityUnits of the tables
        Provisioned Throughput.
    :ivar schema: The Schema object associated with the table.
    """

    def __init__(self, layer2, response=None):
        self.layer2 = layer2
        self._dict = {}
        self.update_from_response(response)

    def __repr__(self):
        return 'Table(%s)' % self.name

    @property
    def name(self):
        return self._dict['TableName']
    
    @property
    def create_time(self):
        return self._dict['CreationDateTime']
    
    @property
    def status(self):
        return self._dict['TableStatus']
    
    @property
    def item_count(self):
        return self._dict['ItemCount']
    
    @property
    def size_bytes(self):
        return self._dict['TableSizeBytes']
    
    @property
    def schema(self):
        return self._schema

    @property
    def read_units(self):
        return self._dict['ProvisionedThroughput']['ReadCapacityUnits']
    
    @property
    def write_units(self):
        return self._dict['ProvisionedThroughput']['WriteCapacityUnits']
    
    def update_from_response(self, response):
        """
        Update the state of the Table object based on the response
        data received from Amazon DynamoDB.
        """
        if 'Table' in response:
            self._dict.update(response['Table'])
        elif 'TableDescription' in response:
            self._dict.update(response['TableDescription'])
        if 'KeySchema' in self._dict:
            self._schema = Schema(self._dict['KeySchema'])

    def refresh(self, wait_for_active=False, retry_seconds=5):
        """
        Refresh all of the fields of the Table object by calling
        the underlying DescribeTable request.

        :type wait_for_active: bool
        :param wait_for_active: If True, this command will not return
            until the table status, as returned from Amazon DynamoDB, is
            'ACTIVE'.

        :type retry_seconds: int
        :param retry_seconds: If wait_for_active is True, this
            parameter controls the number of seconds of delay between
            calls to update_table in Amazon DynamoDB.  Default is 5 seconds.
        """
        done = False
        while not done:
            response = self.layer2.describe_table(self.name)
            self.update_from_response(response)
            if wait_for_active:
                if self.status == 'ACTIVE':
                    done = True
                else:
                    time.sleep(retry_seconds)
            else:
                done = True

    def update_throughput(self, read_units, write_units):
        """
        Update the ProvisionedThroughput for the Amazon DynamoDB Table.

        :type read_units: int
        :param read_units: The new value for ReadCapacityUnits.
        
        :type write_units: int
        :param write_units: The new value for WriteCapacityUnits.
        """
        self.layer2.update_throughput(self, read_units, write_units)
        
    def delete(self):
        """
        Delete this table and all items in it.  After calling this
        the Table objects status attribute will be set to 'DELETING'.
        """
        self.layer2.delete_table(self)

    def get_item(self, hash_key, range_key=None,
                 attributes_to_get=None, consistent_read=False,
                 item_class=Item):
        """
        Retrieve an existing item from the table.

        :type hash_key: int|long|float|str|unicode
        :param hash_key: The HashKey of the requested item.  The
            type of the value must match the type defined in the
            schema for the table.
        
        :type range_key: int|long|float|str|unicode
        :param range_key: The optional RangeKey of the requested item.
            The type of the value must match the type defined in the
            schema for the table.
            
        :type attributes_to_get: list
        :param attributes_to_get: A list of attribute names.
            If supplied, only the specified attribute names will
            be returned.  Otherwise, all attributes will be returned.

        :type consistent_read: bool
        :param consistent_read: If True, a consistent read
            request is issued.  Otherwise, an eventually consistent
            request is issued.

        :type item_class: Class
        :param item_class: Allows you to override the class used
            to generate the items. This should be a subclass of
            :class:`boto.dynamodb.item.Item`
        """
        return self.layer2.get_item(self, hash_key, range_key,
                                    attributes_to_get, consistent_read,
                                    item_class)
    lookup = get_item
    
    def has_item(self, hash_key, range_key=None, consistent_read=False):
        """
        Checks the table to see if the Item with the specified ``hash_key``
        exists. This may save a tiny bit of time/bandwidth over a
        straight :py:meth:`get_item` if you have no intention to touch
        the data that is returned, since this method specifically tells
        Amazon not to return anything but the Item's key.

        :type hash_key: int|long|float|str|unicode
        :param hash_key: The HashKey of the requested item.  The
            type of the value must match the type defined in the
            schema for the table.

        :type range_key: int|long|float|str|unicode
        :param range_key: The optional RangeKey of the requested item.
            The type of the value must match the type defined in the
            schema for the table.

        :type consistent_read: bool
        :param consistent_read: If True, a consistent read
            request is issued.  Otherwise, an eventually consistent
            request is issued.

        :rtype: bool
        :returns: ``True`` if the Item exists, ``False`` if not.
        """
        try:
            # Attempt to get the key. If it can't be found, it'll raise
            # an exception.
            self.get_item(hash_key, range_key=range_key,
                          # This minimizes the size of the response body.
                          attributes_to_get=[hash_key],
                          consistent_read=consistent_read)
        except dynamodb_exceptions.DynamoDBKeyNotFoundError:
            # Key doesn't exist.
            return False
        return True

    def new_item(self, hash_key, range_key=None, attrs=None):
        """
        Return an new, unsaved Item which can later be PUT to
        Amazon DynamoDB.
        """
        return Item(self, hash_key, range_key, attrs)

    def query(self, hash_key, range_key_condition=None,
              attributes_to_get=None, request_limit=None,
              max_results=None, consistent_read=False,
              scan_index_forward=True, exclusive_start_key=None,
              item_class=Item):
        """
        Perform a query on the table.
        
        :type hash_key: int|long|float|str|unicode
        :param hash_key: The HashKey of the requested item.  The
            type of the value must match the type defined in the
            schema for the table.

        :type range_key_condition: dict
        :param range_key_condition: A dict where the key is either
            a scalar value appropriate for the RangeKey in the schema
            of the database or a tuple of such values.  The value 
            associated with this key in the dict will be one of the
            following conditions:

            'EQ'|'LE'|'LT'|'GE'|'GT'|'BEGINS_WITH'|'BETWEEN'

            The only condition which expects or will accept a tuple
            of values is 'BETWEEN', otherwise a scalar value should
            be used as the key in the dict.
        
        :type attributes_to_get: list
        :param attributes_to_get: A list of attribute names.
            If supplied, only the specified attribute names will
            be returned.  Otherwise, all attributes will be returned.

        :type request_limit: int
        :param request_limit: The maximum number of items to retrieve
            from Amazon DynamoDB on each request.  You may want to set
            a specific request_limit based on the provisioned throughput
            of your table.  The default behavior is to retrieve as many
            results as possible per request.

        :type max_results: int
        :param max_results: The maximum number of results that will
            be retrieved from Amazon DynamoDB in total.  For example,
            if you only wanted to see the first 100 results from the
            query, regardless of how many were actually available, you
            could set max_results to 100 and the generator returned
            from the query method will only yeild 100 results max.

        :type consistent_read: bool
        :param consistent_read: If True, a consistent read
            request is issued.  Otherwise, an eventually consistent
            request is issued.

        :type scan_index_forward: bool
        :param scan_index_forward: Specified forward or backward
            traversal of the index.  Default is forward (True).

        :type exclusive_start_key: list or tuple
        :param exclusive_start_key: Primary key of the item from
            which to continue an earlier query.  This would be
            provided as the LastEvaluatedKey in that query.

        :type item_class: Class
        :param item_class: Allows you to override the class used
            to generate the items. This should be a subclass of
            :class:`boto.dynamodb.item.Item`
        """
        return self.layer2.query(self, hash_key, range_key_condition,
                                 attributes_to_get, request_limit,
                                 max_results, consistent_read,
                                 scan_index_forward, exclusive_start_key,
                                 item_class=item_class)

    def scan(self, scan_filter=None,
             attributes_to_get=None, request_limit=None, max_results=None,
             count=False, exclusive_start_key=None, item_class=Item):
        """
        Scan through this table, this is a very long
        and expensive operation, and should be avoided if
        at all possible.

        :type scan_filter: dict
        :param scan_filter: A Python version of the
            ScanFilter data structure.

        :type attributes_to_get: list
        :param attributes_to_get: A list of attribute names.
            If supplied, only the specified attribute names will
            be returned.  Otherwise, all attributes will be returned.

        :type request_limit: int
        :param request_limit: The maximum number of items to retrieve
            from Amazon DynamoDB on each request.  You may want to set
            a specific request_limit based on the provisioned throughput
            of your table.  The default behavior is to retrieve as many
            results as possible per request.

        :type max_results: int
        :param max_results: The maximum number of results that will
            be retrieved from Amazon DynamoDB in total.  For example,
            if you only wanted to see the first 100 results from the
            query, regardless of how many were actually available, you
            could set max_results to 100 and the generator returned
            from the query method will only yeild 100 results max.

        :type count: bool
        :param count: If True, Amazon DynamoDB returns a total
            number of items for the Scan operation, even if the
            operation has no matching items for the assigned filter.

        :type exclusive_start_key: list or tuple
        :param exclusive_start_key: Primary key of the item from
            which to continue an earlier query.  This would be
            provided as the LastEvaluatedKey in that query.

        :type item_class: Class
        :param item_class: Allows you to override the class used
            to generate the items. This should be a subclass of
            :class:`boto.dynamodb.item.Item`

        :rtype: generator
        """
        return self.layer2.scan(self, scan_filter, attributes_to_get,
                                request_limit, max_results,
                                exclusive_start_key, item_class=item_class)