[jira] [Work logged] (BEAM-9008) Add readAll() method to CassandraIO

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/BEAM-9008?focusedWorklogId=619679&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-619679 ]

ASF GitHub Bot logged work on BEAM-9008:
----------------------------------------

                Author: ASF GitHub Bot
            Created on: 07/Jul/21 00:58
            Start Date: 07/Jul/21 00:58
    Worklog Time Spent: 10m 
      Work Description: vmarquez commented on pull request #10546:
URL: https://github.com/apache/beam/pull/10546#issuecomment-875186528


   @aromanenko-dev @iemejia I haven't heard anything in months,  still interested in this contribution? 


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Issue Time Tracking
-------------------

    Worklog Id:     (was: 619679)
    Time Spent: 17h 20m  (was: 17h 10m)

> Add readAll() method to CassandraIO
> -----------------------------------
>
>                 Key: BEAM-9008
>                 URL: https://issues.apache.org/jira/browse/BEAM-9008
>             Project: Beam
>          Issue Type: New Feature
>          Components: io-java-cassandra
>    Affects Versions: 2.16.0
>            Reporter: vincent marquez
>            Priority: P3
>          Time Spent: 17h 20m
>  Remaining Estimate: 0h
>
> When querying a large cassandra database, it's often *much* more useful to programatically generate the queries needed to to be run rather than reading all partitions and attempting some filtering.  
> As an example:
> {code:java}
> public class Event { 
>    @PartitionKey(0) public UUID accountId;
>    @PartitionKey(1)public String yearMonthDay; 
>    @ClusteringKey public UUID eventId;  
>    //other data...
> }{code}
> If there is ten years worth of data, you may want to only query one year's worth.  Here each token range would represent one 'token' but all events for the day. 
> {code:java}
> Set<UUID> accounts = getRelevantAccounts();
> Set<String> dateRange = generateDateRange("2018-01-01", "2019-01-01");
> PCollection<TokenRange> tokens = generateTokens(accounts, dateRange); 
> {code}
>  
>  I propose an additional _readAll()_ PTransform that can take a PCollection of token ranges and can return a PCollection<T> of what the query would return. 
> *Question: How much code should be in common between both methods?* 
> Currently the read connector already groups all partitions into a List of Token Ranges, so it would be simple to refactor the current read() based method to a 'ParDo' based one and have them both share the same function.  Reasons against sharing code between read and readAll
>  * Not having the read based method return a BoundedSource connector would mean losing the ability to know the size of the data returned
>  * Currently the CassandraReader executes all the grouped TokenRange queries *asynchronously* which is (maybe?) fine when all that's happening is splitting up all the partition ranges but terrible for executing potentially millions of queries. 
>  Reasons _for_ sharing code would be simplified code base and that both of the above issues would most likely have a negligable performance impact. 
>  
>  
>  



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