# Will only one thread be used to search one shard internal lucene or one thread per segment?

**URL:** <https://discuss.elastic.co/t/will-only-one-thread-be-used-to-search-one-shard-internal-lucene-or-one-thread-per-segment/59789>\
**Category:** Elasticsearch\
**Created:** [September 5, 2016, 8:22am UTC](https://discuss.elastic.co/t/will-only-one-thread-be-used-to-search-one-shard-internal-lucene-or-one-thread-per-segment/59789 "2016-09-05T08:22:13Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![makeyang](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@makeyang](https://discuss.elastic.co/u/makeyang)\
**Post date:** [September 5, 2016, 8:22am UTC](https://discuss.elastic.co/t/will-only-one-thread-be-used-to-search-one-shard-internal-lucene-or-one-thread-per-segment/59789/1 "2016-09-05T08:22:13Z")

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will one thread be used to search one shard or lucene will manage the index for indexreader internally?

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**Author:** ![jimczi](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/jimczi/32/47985_2.png) [@jimczi](https://discuss.elastic.co/u/jimczi)\
**Post date:** [September 5, 2016, 8:37am UTC](https://discuss.elastic.co/t/will-only-one-thread-be-used-to-search-one-shard-internal-lucene-or-one-thread-per-segment/59789/2 "2016-09-05T08:37:23Z")

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The processing of the segments is sequential (one after the other) with only one thread responsible of the collect. The parallelization is done at the shard level only.

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [July 5, 2017, 10:22pm UTC](https://discuss.elastic.co/t/will-only-one-thread-be-used-to-search-one-shard-internal-lucene-or-one-thread-per-segment/59789/3 "2017-07-05T22:22:32Z")

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