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https://issues.apache.org/jira/browse/IGNITE-18474?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Vladislav Pyatkov resolved IGNITE-18474.
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Resolution: Won't Fix
> Read sql queries has significant number of RAFT write commands
> --------------------------------------------------------------
>
> Key: IGNITE-18474
> URL: https://issues.apache.org/jira/browse/IGNITE-18474
> Project: Ignite
> Issue Type: Task
> Reporter: Kirill Gusakov
> Assignee: Vladislav Pyatkov
> Priority: Major
> Labels: ignite-3
>
> It is counterintuitive, but at the moment usual {{select * from table where
> pk = 1}} query produces even more raft WriteCommands, than insert query.
> The reason is: we have numberOfPartitions*TxCleanupCommand + FinishTxCommand
> for each select query. With the default number of partitons 25 and 1-node
> installation we will have 26 synced writes to rocksDB per query. Together
> with https://issues.apache.org/jira/browse/IGNITE-18475 it blows up our
> latency in 10times per simple select by primary key query.
>
> Possible solution:
> - Detect, that we have only select query in transaction and use read-only
> path for these type of queries
> h3. Implementation Notes
> Core idea is to extend tx meta with an information about the fact whether
> data modificatoin was involved or not during transaction. Within code it
> means that we should check ReplicaRequest.requestType (some casts involved,
> becase replicaRequest is actually a method of SingleRowReplicaRequest,
> MultipleRowReplicaRequest) inside both enlistInTx and set some sort of
> boolean InternalTransaction#dataModificationIntent to true. Please pay
> attetion that should be parition or in other words primary replica specific
> state. Meaning that each enlisted partition/primaryReplica will have it's own
> dataModificationIntent flag.
> That flags should be propagated along with TxFinishReplicaRequest and
> txCleanupReplicaRequest in order to adjust
> PartitionReplicaListener#processTxCleanupAction meaning that it's not
> nessesary to replicate txCleanupCommand in there were no data modifications
> involved.
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