Thanks Michael and Shawn for the detailed response. I was later able to
pull the full history using gitk; and found the commits behind this patch.

Mike:

So, in solr 4.5.0 ; some earlier developer has added code and config to set
applyAllDeletes to false when we reindex all the data.  At the moment, I am
not sure about the performance gain by this.

<!-- Whether to check and apply deletes on flushing of segments.
     Defaults to true and it only makes sense to set this to false
     if you know for sure that there are no deletes performed on the
     shard, i.e. when performing a full index -->


I am investigating the question, if this change is still needed in 6.5.1 or
can this be achieved by any other configuration?

For now, we are not planning to use NRT and solrCloud.


Thanks
Nawab

On Sun, May 28, 2017 at 9:26 AM, Michael McCandless <
luc...@mikemccandless.com> wrote:

> Sorry, yes, that commit was one of many on a feature branch I used to work
> on LUCENE-5438, which added near-real-time index replication to Lucene.
> Before this change, Lucene's replication module required a commit in order
> to replicate, which is a heavy operation.
>
> The writeAllDeletes boolean option asks Lucene to move all recent deletes
> (tombstone bitsets) to disk while opening the NRT (near-real-time) reader.
>
> Normally Lucene won't always do that, and will instead carry the bitsets
> in memory from writer to reader, for reduced refresh latency.
>
> What sort of custom changes do you have in this part of Lucene?
>
> Mike McCandless
>
> http://blog.mikemccandless.com
>
> On Sat, May 27, 2017 at 10:35 PM, Nawab Zada Asad Iqbal <khi...@gmail.com>
> wrote:
>
>> Hi all
>>
>> I am looking at following change in lucene-solr which doen't mention any
>> JIRA. How can I know more about it?
>>
>> "1ae7291 Mike McCandless on 1/24/16 at 3:17 PM current patch"
>>
>> Specifically, I am interested in what 'writeAllDeletes'  does in the
>> following method. Let me know if it is very stupid question and I should
>> have done something else before emailing here.
>>
>> static DirectoryReader open(IndexWriter writer, SegmentInfos infos,
>> boolean applyAllDeletes, boolean writeAllDeletes) throws IOException {
>>
>> Background: We are running solr4.5 and upgrading to 6.5.1. We have
>> some custom code in this area, which we need to merge.
>>
>>
>> Thanks
>>
>> Nawab
>>
>
>

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