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https://issues.apache.org/jira/browse/HBASE-18097?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16029861#comment-16029861
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Enis Soztutar commented on HBASE-18097:
---------------------------------------
bq. The first part for saving 1 RPC request is already implemented as a part of
HBASE-17508, where the scannerId is set to -1 whenever results are not left in
region.
Maybe change the title to focus on the second part then.
Protobuf repeated fields in proto-2 encoding will not use extra bytes for the
array representation (unless packed=true). However, you are right that, for
every row in the ScanResponse object, we are setting a bool in the repeated
field like this:
{code}
2017-05-23 18:06:42,133 TRACE [B.fifo.QRpcServer.handler=9,queue=1,port=16020]
ipc.RpcServer: callId: 384494 service: ClientService methodName: Scan size: 33
connection: <some_ip> param: scanner_id: 12244464 number_of_rows: 100
close_scanner: false next_call_seq: 384492 client_handles_partials: true
client_handles_heartbeats: true renew: false connection: <some_ip>, response
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
cells_per_result: 5 cells_per_result: 5 cells_per_result: 5 cells_per_result: 5
scanner_id: 12244464 more_results: true ttl: 60000 stale: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
partial_flag_per_result: false partial_flag_per_result: false
more_results_in_region: true heartbeat_message: false queueTime: 0
processingTime: 1 totalTime: 1
{code}
The array of {{partial_flag_per_result}} is a waste of bandwidth space.
> Client can save 1 RPC call for CloseScannerRequest
> --------------------------------------------------
>
> Key: HBASE-18097
> URL: https://issues.apache.org/jira/browse/HBASE-18097
> Project: HBase
> Issue Type: Improvement
> Reporter: Karan Mehta
>
> Starting version 1.3, HBase automatically closes scanner on server side
> whenever the results are exhausted and corresponding bits are set in the
> {{ScanResponse}} proto returned to the client. We can use that info to
> eliminate the closeScanRequest RPC call, thereby saving 1 RPC per region per
> scan. This can be particularly useful for tables with more regions.
> Also, currently the {{ScanResponse}} proto sends out 1 bit per {{Result}}
> that it has embeds inside the {{CellScanner}} to indicate if it is partial or
> not.
> {code}
> // In every RPC response there should be at most a single partial result.
> Furthermore, if
> // there is a partial result, it is guaranteed to be in the last position
> of the array.
> {code}
> According to client, only the last result can be partial, thus this repeated
> bool can be converted to a bool, thus reducing overhead of serialization and
> deserialization of the array. This will break wire compatibility therefore
> this is something to look for in upcoming versions.
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