[jira] [Commented] (KUDU-2437) Split a tablet into primary key ranges by size

["yangz (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KUDU-2437?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16750687#comment-16750687 ] 

yangz commented on KUDU-2437:
-----------------------------

Hi [~granthenke] , we give a new issue KUDU-2670 to do this.

> Split a tablet into primary key ranges by size
> ----------------------------------------------
>
>                 Key: KUDU-2437
>                 URL: https://issues.apache.org/jira/browse/KUDU-2437
>             Project: Kudu
>          Issue Type: Improvement
>          Components: client, tablet
>            Reporter: Xu Yao
>            Assignee: Xu Yao
>            Priority: Major
>             Fix For: 1.8.0
>
>
> When reading data in a kudu table using spark, if there is a large amount of data in the tablet, reading the data takes a long time. The reason is that KuduRDD uses a tablet to generate the scanToken, so a spark task needs to process all the data in a tablet. 
> We think that TabletServer should provide an RPC interface, which can be split tablet into multiple primary key ranges by size. The kudu-client can choose whether to perform parallel scan according to the case.
> RPC interface:
> {code:java}
> // A split key range request. Split tablet to key ranges, the request
> // doesn't change layout of tablet.
> message SplitKeyRangeRequestPB {
>  required bytes tablet_id = 1;
>  // Encoded primary key to begin scanning at (inclusive).
>  optional bytes start_primary_key = 2 [(kudu.REDACT) = true];
>  // Encoded primary key to stop scanning at (exclusive).
>  optional bytes stop_primary_key = 3 [(kudu.REDACT) = true];
>  // Number of bytes to try to return in each chunk. This is a hint.
>  // The tablet server may return chunks larger or smaller than this value.
>  optional uint64 target_chunk_size_bytes = 4;
>  // The columns to consider when chunking.
>  // If specified, then the size estimate used for 'target_chunk_size_bytes'
>  // should only include these columns. This can be used if a query will
>  // only scan a certain subset of the columns.
>  repeated ColumnSchemaPB columns = 5;
> }
> // The primary key range of a Kudu tablet.
> message KeyRangePB {
>  // Encoded primary key to begin scanning at (inclusive).
>  optional bytes start_primary_key = 1 [(kudu.REDACT) = true];
>  // Encoded primary key to stop scanning at (exclusive).
>  optional bytes stop_primary_key = 2 [(kudu.REDACT) = true];
>  // Number of bytes in chunk.
>  required uint64 size_bytes_estimates = 3;
> }
> message SplitKeyRangeResponsePB {
>  // The error, if an error occurred with this request.
>  optional TabletServerErrorPB error = 1;
>  repeated KeyRangePB ranges = 2;
> }
> {code}
>  



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