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From Keith Turner <ke...@deenlo.com>
Subject Re: Query Statistics
Date Wed, 17 Apr 2013 15:11:49 GMT
On Wed, Apr 17, 2013 at 10:55 AM, Parker, Matthew - IS
<Matthew.Parker@exelisinc.com> wrote:
> Is there a way to collect statistics about how many tablet servers processed
> a query? Or any statistics for that matter?

The batch scanner does not provide this type of info.   It could be
estimated with the following code.  This code will determine what
tablet servers the batch scanner would talk to.  When executing the
query its possible that tablets may move and different tablet servers
may be contacted.

    List<Range> ranges; //ranges passed to batch scanner

    tableID = new Text(connector.tableOperations().tableIdMap().get(tableName));
    TabletLocator locator = TabletLocator.getInstance(instance,
credentials, tableID);

    Map<String,Map<KeyExtent,List<Range>>> binnedRanges = new
HashMap<String,Map<KeyExtent,List<Range>>>();

    List<Range> failures = locator.binRanges(ranges, binnedRanges);

    if(failures.size() == 0){
      System.out.println("Number of servers queried :
"+binnedRanges.keySet().size());
    }else{
      //retry?  some of the tablets needed for the query are not
assigned at the moment... the batch scanner will just retry in this
case.
    }

Keith

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