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Date: Fri, 30 Dec 2011 21:16:17 +0200
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 <CAPpvZ9AC4rtGDAqL7UBQkBQjjvjK9Vnj0nUCvggBx8TuVnHc-g@mail.gmail.com>
Subject: Re: question regarding code
From: Mikael Sitruk <mikael.sitruk@gmail.com>
To: dev@hbase.apache.org
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it should not be a problem
i'll try
Mikael.S

On Fri, Dec 30, 2011 at 9:10 PM, <yuzhihong@gmail.com> wrote:

> Mikael:
> Can you upload a patch ?
>
> Thanks
>
>
>
> On Dec 30, 2011, at 11:06 AM, Mikael Sitruk <mikael.sitruk@gmail.com>
> wrote:
>
> > Thanks to all of you, jira -
> > HBASE-5110<https://issues.apache.org/jira/browse/HBASE-5110> (code
> > enhancement - remove unnecessary if-checks in every loop in HLog class)
> >
> > Happy new year for all of you.
> >
> > Mikael.S
> >
> > On Fri, Dec 30, 2011 at 6:34 AM, Lars H <lhofhansl@yahoo.com> wrote:
> >
> >> oh no no... please file a jira and help us make HBase better.
> >>
> >> Mikael Sitruk <mikael.sitruk@gmail.com> schrieb:
> >>
> >>> Lars hi
> >>>
> >>> This method will be called anytime that old log exist and might be
> cleaned
> >>> (HLog.cleanOldsLogs()) and there are too much logs.
> >>> It is called from LogRoller thread, Hlog creation, and
> >> metaUtils.shutdown()
> >>> (code in 0.90.1 - also present at least in those classes in trunk),
> >>> The creation of Arraylist is approx 24 bytes (8 for Arraylist object,
> 12
> >>> for the array member and 4 for the int member) if I didn't forgot
> >>> something, nevertheless the "if" will not be checked for each region
> >> having
> >>> an older log file (which will occurs a lot if you have heavy writes
> >>> scenarios).
> >>> This is true that this will create garbage (in case it will not be
> used)
> >>> but this is a short lived object, it will be collected immediately
> with a
> >>> minor garbage collection. It would have be more problematic if the
> object
> >>> was long lived.
> >>>
> >>> Anyway you are the one to decide, if you accept a jira, i will open
> one,
> >>> just let me know.
> >>>
> >>> Regards,
> >>> Mikael.S
> >>>
> >>>
> >>> On Thu, Dec 29, 2011 at 6:54 PM, lars hofhansl <lhofhansl@yahoo.com>
> >> wrote:
> >>>
> >>>> The only downside is that the ArrayList now is always created, even if
> >> it
> >>>> is not needed, thereby producing unnecessary garbage.
> >>>> I have not bearing how frequently we'll get here and find no relevant
> >>>> regions, though.
> >>>>
> >>>>
> >>>> -- Lars
> >>>>
> >>>>
> >>>> ----- Original Message -----
> >>>> From: Harsh J <harsh@cloudera.com>
> >>>> To: dev@hbase.apache.org
> >>>> Cc:
> >>>> Sent: Thursday, December 29, 2011 12:51 AM
> >>>> Subject: Re: question regarding code
> >>>>
> >>>> Yeah that'd work too. File a JIRA with the change?
> >>>>
> >>>> On 29-Dec-2011, at 2:12 PM, Mikael Sitruk wrote:
> >>>>
> >>>>> Hi all
> >>>>>
> >>>>> I have question on some code (taken from HLog) see below
> >>>>>
> >>>>>
> >>>>> static byte [][] findMemstoresWithEditsEqualOrOlderThan(final long
> >>>>> oldestWALseqid,
> >>>>>     final Map<byte [], Long> regionsToSeqids) {
> >>>>>   //  This method is static so it can be unit tested the easier.
> >>>>>   List<byte []> regions = null;
> >>>>>   for (Map.Entry<byte [], Long> e: regionsToSeqids.entrySet()) {
> >>>>>     if (e.getValue().longValue() <= oldestWALseqid) {
> >>>>>       if (regions == null) regions = new ArrayList<byte []>();
> >>>>>       regions.add(e.getKey());
> >>>>>     }
> >>>>>   }
> >>>>>   return regions == null?
> >>>>>     null: regions.toArray(new byte [][]
> >> {HConstants.EMPTY_BYTE_ARRAY});
> >>>>> }
> >>>>>
> >>>>> Shouldn't be better to remove the if in the loop doing as follow?
> >>>>>
> >>>>> static byte [][] findMemstoresWithEditsEqualOrOlderThan(final long
> >>>>> oldestWALseqid,
> >>>>>     final Map<byte [], Long> regionsToSeqids) {
> >>>>>   //  This method is static so it can be unit tested the easier.
> >>>>>   List<byte []> regions = new ArrayList<byte []>();
> >>>>>   for (Map.Entry<byte [], Long> e: regionsToSeqids.entrySet()) {
> >>>>>     if (e.getValue().longValue() <= oldestWALseqid) {
> >>>>>       //if (regions == null) regions = new ArrayList<byte []>();
> >>>>>       regions.add(e.getKey());
> >>>>>     }
> >>>>>   }
> >>>>>   return regions.size() == 0?
> >>>>>     null: regions.toArray(new byte [][]
> >> {HConstants.EMPTY_BYTE_ARRAY});
> >>>>> }
> >>>>>
> >>>>> regards,
> >>>>>
> >>>>> Mikael.S
> >>>>
> >>>
> >>>
> >>>
> >>> --
> >>> Mikael.S
> >>
> >
> >
> >
> > --
> > Mikael.S
>


-- 
Mikael.S

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