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From "Vladimir Rodionov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13890) Get/Scan from MemStore only (Client API)
Date Mon, 06 Jul 2015 23:39:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13890?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14615894#comment-14615894
] 

Vladimir Rodionov commented on HBASE-13890:
-------------------------------------------

The new API was added to *OperationsWithAttributes*: 

{code}
  /**
   * This method allows you to set in-memory-only operation mode.
   * Queries: Get and Scan as well as Increment and Append will
   * work only on data in RAM (MemStore). 
   * If data is missing in RAM, the following will be returned:
   *  Empty Result for Get, Increment, Append and Scan
   *  
   */
  public OperationWithAttributes setMemstoreOnly(boolean v){
    setAttribute(MEMSTORE_ONLY_ATTRIBUTE, Bytes.toBytes(v));
    return this;
  }
  /**
   * Checks if we are in-memory-only mode
   * @return true, if yes
   */
  public boolean isMemstoreOnly(){
    byte[] attr = getAttribute(MEMSTORE_ONLY_ATTRIBUTE);
    return attr != null && Bytes.toBoolean(attr) == true;
  }
{code}

> Get/Scan from MemStore only (Client API)
> ----------------------------------------
>
>                 Key: HBASE-13890
>                 URL: https://issues.apache.org/jira/browse/HBASE-13890
>             Project: HBase
>          Issue Type: New Feature
>          Components: API, Client, Scanners
>            Reporter: Vladimir Rodionov
>            Assignee: Vladimir Rodionov
>         Attachments: HBASE-13890-v1.patch
>
>
> This is short-circuit read for get/scan when recent data (version) of a cell can be found
only in MemStore (with very high probability). 
> Good examples are: Atomic counters and appends. This feature will allow to bypass completely
store file scanners and improve performance and latency.



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