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https://issues.apache.org/jira/browse/CASSANDRA-16226?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Caleb Rackliffe updated CASSANDRA-16226:
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Test and Documentation Plan:
The patch includes a new in-JVM upgrade test that exercises the 2.2 -> 3.0
upgrade path were an existing table uses COMPACT STORAGE and we hit the
particular scenario outlined in the description. Outside that, the interesting
parts of the regression suite are the tests around row deletions and cell
deletions where only a primary key remains.
Performance should also be improved significantly in this scenario, so a smoke
test to verify that would be helpful. (There should be zero impact on
non-compact tables.)
Status: Patch Available (was: In Progress)
[3.0 patch|https://github.com/apache/cassandra/pull/789],
[CircleCI|https://app.circleci.com/pipelines/github/maedhroz/cassandra/137/workflows/40098e98-f383-4bcd-ba01-be9a11a90190]
> COMPACT STORAGE SSTables created before 3.0 are not correctly skipped by
> timestamp due to missing primary key liveness info
> ---------------------------------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-16226
> URL: https://issues.apache.org/jira/browse/CASSANDRA-16226
> Project: Cassandra
> Issue Type: Bug
> Components: Legacy/Local Write-Read Paths
> Reporter: Caleb Rackliffe
> Assignee: Caleb Rackliffe
> Priority: Normal
> Labels: perfomance, upgrade
> Fix For: 3.0.x, 3.11.x, 4.0-beta
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> This was discovered while tracking down a spike in the number of SSTables
> per read for a COMPACT STORAGE table after a 2.1 -> 3.0 upgrade. Before 3.0,
> there is no direct analog of 3.0's primary key liveness info. When we upgrade
> 2.1 COMPACT STORAGE SSTables to the mf format, we simply don't write row
> timestamps, even if the original mutations were INSERTs. On read, when we
> look at SSTables in order from newest to oldest max timestamp, we expect to
> have this primary key liveness information to determine whether we can skip
> older SSTables after finding completely populated rows.
> ex. I have three SSTables in a COMPACT STORAGE table with max timestamps
> 1000, 2000, and 3000. There are many rows in a particular partition, making
> filtering on the min and max clustering effectively a no-op. All data is
> inserted, and there are no partial updates. A fully specified row with
> timestamp 2500 exists in the SSTable with a max timestamp of 3000. With a
> proper row timestamp in hand, we can easily ignore the SSTables w/ max
> timestamps of 1000 and 2000. Without it, we read 3 SSTables instead of 1,
> which likely means a significant performance regression.
> The following test illustrates this difference in behavior between 2.1 and
> 3.0:
> https://github.com/maedhroz/cassandra/commit/84ce9242bedd735ca79d4f06007d127de6a82800
> A solution here might be as simple as having
> {{SinglePartitionReadCommand#canRemoveRow()}} only inspect primary key
> liveness information for non-compact/CQL tables. Tombstones seem to be
> handled at a level above that anyway. (One potential problem with that is
> whether or not the distinction will continue to exist in 4.0, and dropping
> compact storage from a table doesn't magically make pk liveness information
> appear.)
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