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