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  1. Apache Trafodion
  2. TRAFODION-2234

turn aligned row format for tables to ON by default



    • Type: Improvement
    • Status: Closed
    • Priority: Minor
    • Resolution: Fixed
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: None
    • Labels:


      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.




            • Assignee:
              anoopsharma Anoop Sharma
              anoopsharma Anoop Sharma
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