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# ask-ai
f

Fernando Cagua

02/20/2024, 6:22 PM
What’s the best way to get the partition keys between a start and end datetime in a daily partition definition ?
s

Scout

02/20/2024, 6:22 PM
To get the partition keys between a start and end datetime in a daily partition definition, you would typically define a
DailyPartitionsDefinition
with the
start_date
and
end_date
parameters. The
start_date
parameter specifies the first date in the set of partitions, and the
end_date
parameter specifies the last date (excluding) in the set of partitions. Both parameters can be provided in either a datetime or string format. Here's an example from the documentation that illustrates how to create a `DailyPartitionsDefinition`:
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python
DailyPartitionsDefinition(start_date="2022-03-12")
# creates partitions (2022-03-12-00:00, 2022-03-13-00:00), (2022-03-13-00:00, 2022-03-14-00:00), ...
If you want to specify an end date, you can do so like this:
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python
DailyPartitionsDefinition(start_date="2022-03-12", end_date="2022-03-15")
# creates partitions (2022-03-12-00:00, 2022-03-13-00:00), (2022-03-13-00:00, 2022-03-14-00:00), (2022-03-14-00:00, 2022-03-15-00:00)
In this example, the partitions created will include the start date and exclude the end date. The partition keys will be the string representations of the dates for each day in the range, assuming the default date format
%Y-%m-%d
. To retrieve the partition keys for a given
DailyPartitionsDefinition
, you would typically use a method that returns the list of partition keys based on the definition. The documentation does not explicitly provide a code snippet for retrieving the partition keys from a
DailyPartitionsDefinition
, but in practice, you would use the defined partitions definition within the context of a Dagster pipeline or job to iterate over the partitions and perform operations on each partition's data. Dagster Docs button Rolling window timerange partition button Composite Time Window Partitions Definit... button How do I create partitions for only busi... button Thank you for your feedback!
f

Fernando Cagua

02/20/2024, 6:23 PM
@Scout, How to get the specific partition key that corresponds to a single given datetime
s

Scout

02/20/2024, 6:23 PM
To get the specific partition key that corresponds to a single given datetime, you would typically use the datetime to determine which partition it falls into based on your partitioning scheme. If you are using a
DailyPartitionsDefinition
, each partition represents a single day. Here's a step-by-step approach to determine the partition key for a given datetime: 1. Identify the datetime for which you want to find the corresponding partition key. 2. Use the
DailyPartitionsDefinition
that you have defined for your partitions. 3. Compare the given datetime to the start and end times of each partition to find the partition that includes the datetime. The partition key for a daily partition is usually formatted as a string representing the date, often in the format
%Y-%m-%d
. If your datetime falls within the date represented by the partition key, then that is the partition key corresponding to your datetime. For example, if you have a datetime object
my_datetime
and you want to find out which daily partition it belongs to, you could format the datetime as a string in the same format as your partition keys:
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python my_datetime_str = my_datetime.strftime('%Y-%m-%d')
This string
my_datetime_str
is the partition key that corresponds to the given
my_datetime
, assuming that
my_datetime
includes a time component that falls within the day starting at midnight and ending just before midnight of the next day. Please note that the above method assumes that your partitions are defined with a granularity of one day and that the partition keys are strings representing the date in the
%Y-%m-%d
format. If your partitioning scheme or key format is different, you would need to adjust the method accordingly.
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