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https://issues.apache.org/jira/browse/KUDU-3353?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17603321#comment-17603321
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ASF subversion and git services commented on KUDU-3353:
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Commit ec3a9f75b6924a70ecbf08e3805228ad9b92b9f0 in kudu's branch
refs/heads/master from Yingchun Lai
[ https://gitbox.apache.org/repos/asf?p=kudu.git;h=ec3a9f75b ]
KUDU-3353 [schema] Add an immutable attribute on column schema (part 2)
This is a follow-up to b6eedb224f715ad86378a92d25f09c2084b0e2b7.
This patch includes the C++ client-side changes of the "new column
attribute IMMUTABLE" feature, including:
1. Adds a new KuduColumnSpec::Immutable() method to add IMMUTABLE
attribute to a column, and adds a new KuduColumnSpec::Mutable()
method to remove IMMUTABLE attribute from a column.
2. Adds a new KuduColumnSchema::is_immutable() to check if the
attribute is set for a column schema.
3. Adds a new KuduUpsertIgnore operation in the client API: use the
newly added KuduTable::NewUpsertIgnore() to create a new instance
of such operation.
4. Adds unit tests to cover the newly introduced functionality.
5. Small refactoring on the server side.
Change-Id: Id301e313eedd9cc3a494d6b4f3c14fbabe63b436
Reviewed-on: http://gerrit.cloudera.org:8080/18835
Tested-by: Yingchun Lai <[email protected]>
Reviewed-by: Alexey Serbin <[email protected]>
> Support setnx semantic on column
> --------------------------------
>
> Key: KUDU-3353
> URL: https://issues.apache.org/jira/browse/KUDU-3353
> Project: Kudu
> Issue Type: New Feature
> Components: api, server
> Reporter: Yingchun Lai
> Assignee: Yingchun Lai
> Priority: Major
>
> h1. motivation
> In some usage scenarios, Kudu table has a column with semantic of "create
> time", which means it represent the create timestamp of the row. The other
> columns have the similar semantic as before, for example, the user properties
> like age, address, and etc.
> Upstream and Kudu user doesn't know whether a row is exist or not, and every
> cell data is the lastest ingested from, for example, event stream.
> If without the "create time" column, Kudu user can use UPSERT operations to
> write data to the table, every columns with data will overwrite the old data.
> But if with the "create time" column, the cell data will be overwrote by the
> following UPSERT ops, which is not what we expect.
> To achive the goal, we have to read the column out to judge whether the
> column is NULL or not, if it's NULL, we can fill the row with the cell, if
> not NULL, we will drop it from the data before UPSERT, to avoid overwite
> "create time".
> It's expensive, is there a way to avoid a read from Kudu?
> h1. Resolvation
> We can implement column schema with semantic of "update if null". That means
> cell data in changelist will update the base data if the latter is NULL, and
> will ignore updates if it is not NULL.
> So we can use Kudu similarly as before, but only defined the column as
> "update if null" when create table or add column.
>
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