ASF GitHub Bot commented on TRAFODION-2234:

GitHub user anoopsharma00 opened a pull request:


    jira TRAFODION-2234 turn aligned format on, phase 1

    This is phase 1 of aligned format change.
    Dev regressions now run with aligned format tables.
    To test both hbase and aligned format, some tests have explicit
    specification to create hbase format tables.
    Tests that test for features that are currently only available
    with hbase format (like pushdown sel expr) create hbase format tables.
    Many expected files have been updated to reflect aligned format,
    mostly in showddl and explain output.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/anoopsharma00/incubator-trafodion 

Alternatively you can review and apply these changes as the patch at:


To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #718


> turn aligned row format for tables to ON by default
> ---------------------------------------------------
>                 Key: TRAFODION-2234
>                 URL: https://issues.apache.org/jira/browse/TRAFODION-2234
>             Project: Apache Trafodion
>          Issue Type: Improvement
>            Reporter: Anoop Sharma
>            Assignee: Anoop Sharma
>            Priority: Minor
> Columns in Trafodion tables are stored in 2 formats:
> -- regular hbase format where each column is stored as one cell
> -- aligned format where the whole row is packed and stored in one cell
> Aligned row provides performance boost during inserts and selects by
> retrieving one cell from hbase instead of multiple cells. As the number
> of columns in a table increase, perf of aligned format gets better.
> There are some limitations with aligned format:
> -- selection predicates cannot be pushed down to hbase region server
> -- all columns need to be retrieved and updated as packed row in a cell
> -- columns cannot be dropped without reloading the table
> Over time, these limitations will be removed by use of user defined filters
> and coprocessors to select/project rows at hbase region level.
> During perf runs, the pros for aligned format outweigh the cons.
> This jira is being filed to change the default from hbase format row
> to aligned format row. Code for both aligned and hbase format already
> exists and is being used.
> A table can always be created in either of these 2 formats by explicitly
> specifying the format during create time.
> The default can also be changed to off or on by inserting the appropriate
> value in the system defaults table.
> Turning on aligned format as default will be done in 2 phases:
> -- in phase 1, aligned default will be turning on during dev regressions run
>   until it has stabilized.
> -- in phase 2, system default will be changed to aligned. All table created
> without an explicit format specification will be created in aligned format.
> Metadata, repository, privilege and histogram tables will always be 
> created in hbase format. This is needed for backward compatibility.
> Any component or application that doesn't want to depend on the system
> default must explicitly specify the row format in their create ddl.

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