[jira] [Updated] (IGNITE-17856) MvPartitionStorage#scan(UUID) and read(UUID) should return PartitionTimestampCursor and ReadResult

["Alexander Lapin (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IGNITE-17856?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Alexander Lapin updated IGNITE-17856:
-------------------------------------
    Summary: MvPartitionStorage#scan(UUID) and read(UUID) should return PartitionTimestampCursor and ReadResult  (was: MvPartitionStorage#scan(java.util.UUID) should return PartitionTimestampCursor)

> MvPartitionStorage#scan(UUID) and read(UUID) should return PartitionTimestampCursor and ReadResult
> --------------------------------------------------------------------------------------------------
>
>                 Key: IGNITE-17856
>                 URL: https://issues.apache.org/jira/browse/IGNITE-17856
>             Project: Ignite
>          Issue Type: Improvement
>            Reporter: Alexander Lapin
>            Priority: Major
>              Labels: ignite-3
>
> h3. Motivation
> Tx protocol design assumes that data entry exists in the form of a _write intent_ from the moment the entry is changed within transaction to the moment it is either converted to the regular value or removed during tx cleanup phase.
> Read Only transactions because of their lock-less nature may see such writeIntents (corresponding changes were implemented within IGNITE-17720  and IGNITE-17627) and ...
> ... according to tx design updates so does Read Write transactions.
> Let's clarify this in greater detail:
>  * Originally tx finish process firstly converted the write intents into regular values, and only then released the locks. Thus, other RW transactions could never see write intents as they were always waiting for locks to be released.
>  * In the current version of the [TX IEP|https://cwiki.apache.org/confluence/display/IGNITE/IEP-91%3A+Transaction+protocol], the order has been changed to the opposite: locks are released before write Intents conversion, so that not only a RO but also a RW transactions may see the intents.
> All in all, that means that both read and scan RW operations should be updated in a way similar to RO reads and scans were:
> *Definition of Done*
> {code:java}
> Cursor<BinaryRow> scan(UUID txId) {code}
> should be changed as follows
> {code:java}
> PartitionTimestampCursor scan(UUID txId)  {code}
> in order to produce an ability of definition whether the row is writeIntent or not and reading latest non-intent row if the intent belongs to pending transaction.
>  
> Same is about read operation.
> {code:java}
> BinaryRow read(RowId rowId, UUID txId)  {code}
> should be changed as follows
> {code:java}
> ReadResult read(RowId rowId, UUID txId) {code}



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