Nope, I don't think I have that kind of fields.
In my parent entity, 2 properties are indexed : the primary key
(programatically defined based on a String), plus another key (unowned
relationship).
In my child entity, 2 properties as well : the primary key (programatically
defined as well), plus a ListProperty (strict application of Brett's
recommandation) 
I just got lots of com.google.apphosting.api.DeadlineExceededException
exceptions (approx. 30%), which I considered caused from the high number of
shards causing high concurrency somewhere/somehow.

From:  "Ikai Lan (Google)" <ikai.l+gro...@google.com>
Reply-To:  <google-appengine-java@googlegroups.com>
Date:  Wed, 24 Nov 2010 10:29:17 -0800
To:  <google-appengine-java@googlegroups.com>
Subject:  Re: [appengine-java] Mapper & Blobstore bytes read limit

BTW - did you have any data that would have created a sequentially
increasing index?

For instance, a "Created At" timestamp? This sort of thing in a  high write
environment can cause issues: though tablets are essentially sharded, it
means sequential index writes at a high speed, causing tablets to become
"hot" and slow your overall throughput.

--
Ikai Lan 
Developer Programs Engineer, Google App Engine
Blogger: http://googleappengine.blogspot.com
<http://googleappengine.blogspot.com/>
Reddit: http://www.reddit.com/r/appengine
Twitter: http://twitter.com/app_engine



On Wed, Nov 24, 2010 at 10:26 AM, Ikai Lan (Google)
<ikai.l+gro...@google.com <mailto:ikai.l%2bgro...@google.com> > wrote:
> Mind blowing. Awesome!
> 
> 
> --
> Ikai Lan 
> Developer Programs Engineer, Google App Engine
> Blogger: http://googleappengine.blogspot.com
> <http://googleappengine.blogspot.com/>
> Reddit: http://www.reddit.com/r/appengine
> Twitter: http://twitter.com/app_engine
> 
> 
> 
> On Wed, Nov 24, 2010 at 5:54 AM, Cyrille Vincey <crll...@gmail.com> wrote:
>> It works, and the performance is breathtaking :
>> 8.6 million entities (4.3 lines x 2 entities per line) created in 1.5h, using
>> 100 shardsŠ
>> Compared to my previous non-blob-based mapper job, CPU cost remains a little
>> high (190 CPU hours), but I can't complain.
>> Thank you guys.
>> 
>> From:  "Ikai Lan (Google)" <ikai.l+gro...@google.com>
>> Reply-To:  <google-appengine-java@googlegroups.com>
>> Date:  Wed, 17 Nov 2010 16:06:07 -0800
>> 
>> To:  <google-appengine-java@googlegroups.com>
>> Subject:  Re: [appengine-java] Mapper & Blobstore bytes read limit
>> 
>> The bug has been fixed. Check out the latest code from the
>> appengine-mapreduce project.
>> 
>> Note that the ratio between blobstore bytes read and blob size is not 1:1. In
>> my tests they were closer to 10:1. This is expected behavior for the time
>> being. We're working on more options so users can better tune the behavior.
>> 
>> --
>> Ikai Lan 
>> Developer Programs Engineer, Google App Engine
>> Blogger: http://googleappengine.blogspot.com
>> <http://googleappengine.blogspot.com/>
>> Reddit: http://www.reddit.com/r/appengine
>> Twitter: http://twitter.com/app_engine
>> 
>> 
>> 
>> On Wed, Nov 17, 2010 at 2:19 AM, Cyrille Vincey <crll...@gmail.com> wrote:
>>> VERY good news.
>>> Can't wait. Thanks.
>>> 
>>> From:  "Ikai Lan (Google)" <ikai.l+gro...@google.com>
>>> Reply-To:  <google-appengine-java@googlegroups.com>
>>> Date:  Tue, 16 Nov 2010 12:07:59 -0800
>>> 
>>> To:  <google-appengine-java@googlegroups.com>
>>> Subject:  Re: [appengine-java] Mapper & Blobstore bytes read limit
>>> 
>>> We discovered a bug. We're not reading in the entire blob, but we are
>>> reading in far too much data.
>>> 
>>> Fred has a fix waiting in the rafters. I'll post again when it's been
>>> pushed.
>>> 
>>> --
>>> Ikai Lan 
>>> Developer Programs Engineer, Google App Engine
>>> Blogger: http://googleappengine.blogspot.com
>>> <http://googleappengine.blogspot.com/>
>>> Reddit: http://www.reddit.com/r/appengine
>>> Twitter: http://twitter.com/app_engine
>>> 
>>> 
>>> 
>>> On Thu, Nov 4, 2010 at 2:36 AM, Cyrille Vincey <crll...@gmail.com> wrote:
>>>> Not a lot of interesting stuff to say :
>>>> 1. My code is quite as simple as your sample code: the only real difference
>>>> is that I create 2 parent/child entities in a row for one given csv line
>>>> entry.
>>>> 2. My csv file contains 4.3 million lines.
>>>> 2. I launched the mapper job with 10 shards.
>>>> 3. "worker-attempt-XXX" tasks had 20 retries each in average.
>>>> 4. The blobstore bytes read quota (100 Go) got reached within the first 3
>>>> hours.
>>>> 5. Est. 10% of the entities where actually created after 24h (with my
>>>> previous non-blob-based mapper job, those 4.3 million entities where
>>>> created within 1 day)
>>>> 6. Log does not reveal anything interesting.
>>>> 
>>>> I am currently running a new test with a 500,000 lines csv file (20 Mb
>>>> file).
>>>> Performance looks better. To me, blob file size may have an influence on
>>>> the mapper performance.
>>>> 
>>>> If you need more details, let me know.
>>>> 
>>>> From:  "Ikai Lan (Google)" <ikai.l+gro...@google.com>
>>>> Reply-To:  <google-appengine-java@googlegroups.com>
>>>> Date:  Wed, 3 Nov 2010 12:22:10 -0700
>>>> To:  <google-appengine-java@googlegroups.com>
>>>> Subject:  Re: [appengine-java] Mapper & Blobstore bytes read limit
>>>> 
>>>> This behavior doesn't seem right. No, the entire blob should not be getting
>>>> read. We'll look into this.
>>>> 
>>>> Do you have any more details? Could tasks be getting retried?
>>>> 
>>>> --
>>>> Ikai Lan 
>>>> Developer Programs Engineer, Google App Engine
>>>> Blogger: http://googleappengine.blogspot.com
>>>> <http://googleappengine.blogspot.com/>
>>>> Reddit: http://www.reddit.com/r/appengine
>>>> Twitter: http://twitter.com/app_engine
>>>> 
>>>> 
>>>> 
>>>> On Tue, Nov 2, 2010 at 9:42 AM, Cyrille Vincey <crll...@gmail.com> wrote:
>>>>> I've been testing Ikai's bulkload mapper (see url below) with a pretty big
>>>>> csv file (200 Mb).
>>>>> It works great, and I encourage most of you to consider implementing this
>>>>> for entity uploads.
>>>>> 
>>>>> Yet, I do face one last issue with an unexpected quota : blobstore bytes
>>>>> read.
>>>>> This quota cannot be tuned via the billing settings, and it's not clear
>>>>> whether it limits the speed of my process or not when it's reached.
>>>>> 
>>>>> 
>>>>> See ? Yep, it's a lot of bytes readŠ
>>>>> Could someone confirm that the blob csv file is *NOT* fully fetched each
>>>>> time the mapper iterates on a new line ?
>>>>> 
>>>>> (ikai's post)
>>>>> http://ikaisays.com/2010/08/11/using-the-app-engine-mapper-for-bulk-data-i
>>>>> mport/
>>>>> 
>>>>> 
>>>>> -- 
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>>>> 
>>>> 
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>>> 
>>> 
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>> 
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> 


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