# How to calculate the number of slices for a search slicing point-in-time query?

**URL:** <https://discuss.elastic.co/t/how-to-calculate-the-number-of-slices-for-a-search-slicing-point-in-time-query/378798>\
**Category:** Elastic Search\
**Created:** [June 2, 2025, 2:31pm UTC](https://discuss.elastic.co/t/how-to-calculate-the-number-of-slices-for-a-search-slicing-point-in-time-query/378798 "2025-06-02T14:31:10Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![peter8](https://avatars.discourse-cdn.com/v4/letter/p/ee7513/32.png) [@peter8](https://discuss.elastic.co/u/peter8)\
**Post date:** [June 2, 2025, 2:31pm UTC](https://discuss.elastic.co/t/how-to-calculate-the-number-of-slices-for-a-search-slicing-point-in-time-query/378798/1 "2025-06-02T14:31:10Z")

</div>

I have an index with aprox. 1.5M documents and 1 primary shard. The count function for my query shows that I can expect 31357 documents.

When I do the search slicing point-in-time queries for 9 (or less) slices and maximum 10000 documents per slice, I end up with missing documents. (29086 total). I noticed that slice 3 has 10000 documents and the other slices have less than 10000 documents.

The slicing point-in-time query for 10 (or more) slices gives me all 31357 documents. The individual slices have less than 10000 documents.

Is there a formula, so that can calculate the best number of slices to get all documents?

---

<div class="post-metadata">

**Author:** ![Tortoise](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/tortoise/32/147587_2.png) [@Tortoise](https://discuss.elastic.co/u/Tortoise)\
**Post date:** [June 4, 2025, 12:21pm UTC](https://discuss.elastic.co/t/how-to-calculate-the-number-of-slices-for-a-search-slicing-point-in-time-query/378798/2 "2025-06-04T12:21:03Z")

</div>

Hello @peter8 ,

Welcome to the community!!

I tried below way :

```auto
GET kibana_sample_data_logs/_count
{
  "query": {
    "range": {
      "@timestamp": {
        "gte": "2025-06-03T00:00:00Z",
        "lte": "2025-06-04T00:00:00Z"
      }
    }
  }
}

```

**`Output : "count": 232`**

```auto
POST /kibana_sample_data_logs/_search
{
  "size": 0,
  "query": {
    "range": {
      "@timestamp": {
        "gte": "2025-06-03T00:00:00Z",
        "lte": "2025-06-04T00:00:00Z"
      }
    }
  },
  "aggs": {
    "terms_count_per_day": {
      "date_histogram": {
        "field": "@timestamp",
        "fixed_interval": "1d"
      }
      }
    }
  }

```

```auto
**Output snippet :** 

   "hits": {
    "total": {
      "value": 232,
      "relation": "eq"
    },
    "max_score": null,
    "hits": []
  },
  "aggregations": {
    "terms_count_per_day": {
      "buckets": [
        {
          "key_as_string": "2025-06-03T00:00:00.000Z",
          "key": 1748908800000,
          "doc_count": 230
        },
        {
          "key_as_string": "2025-06-04T00:00:00.000Z",
          "key": 1748995200000,
          "doc_count": 2
        }
      ]
    }

```

Now since you want all records & do not want to guess the number of slice , i am not sure if this way it can be considered like range we take fixed as 1day/1week/1month depending upon the available data.

If i have misunderstood your requirement, please share more details.

Thanks!!

---

<div class="post-metadata">

**Author:** ![peter8](https://avatars.discourse-cdn.com/v4/letter/p/ee7513/32.png) [@peter8](https://discuss.elastic.co/u/peter8)\
**Post date:** [June 5, 2025, 7:05am UTC](https://discuss.elastic.co/t/how-to-calculate-the-number-of-slices-for-a-search-slicing-point-in-time-query/378798/3 "2025-06-05T07:05:30Z")

</div>

> [@peter8](#):
>
> calculate the best number of slices to get all documents?

A count request shows that i can expect 31357 documents for a query.  
My assumption is that this will fit in 4 slices of 10000 documents.

So i start with a request for a pit:

`POST /myindex/_pit?keep_alive=5m`

which returns a pit, eg: w8abBAERb3BlbnJkdy...nN3AAA=

Then i do 4 subsequent [slicing point-in-time query](https://www.elastic.co/guide/en/elasticsearch/reference/8.18/point-in-time-api.html#search-slicing) with an increasing slice.id from 0 to 3 and slice.max = 4

```auto
POST /_search
{
  "slice": { "id": "0", "max": 4 },
  "pit": {
    "id":"w8abBAERb3BlbnJkdy...nN3AAA="
  },
  "size":10000,
  "query": { ... }
}

```

```auto
POST /_search
{
  "slice": { "id": "1", "max": 4 },
  "pit": {
    "id":"w8abBAERb3BlbnJkdy...nN3AAA="
  },
  "size":10000,
  "query": { ... }
}

```

```auto
POST /_search
{
  "slice": { "id": "2", "max": 4 },
  "pit": {
    "id":"w8abBAERb3BlbnJkdy...nN3AAA="
  },
  "size":10000,
  "query": { ... }
}

```

```auto
POST /_search
{
  "slice": { "id": "3", "max": 4 },
  "pit": {
    "id":"w8abBAERb3BlbnJkdy...nN3AAA="
  },
  "size":10000,
  "query": { ... }
}

```

slice.id=0 returns 8145 rows  
slice.id=1 returns 10000 rows  
slice.id=2 returns 201 rows  
slice.id=3 returns 5574 rows  
Total 23920 rows but i expected 31357 rows

When i increase the slice.max and query all slices it will return more documents.  
When slice.max = 10 or higher, it will return all rows (and each slice has less than 10000 documents)

The slice.max must be known **before** the first slicing point-in-time query  
My question is how to calculate the best number of slices and get all documents?

---

<div class="post-metadata">

**Author:** ![peter8](https://avatars.discourse-cdn.com/v4/letter/p/ee7513/32.png) [@peter8](https://discuss.elastic.co/u/peter8)\
**Post date:** [June 10, 2025, 12:36pm UTC](https://discuss.elastic.co/t/how-to-calculate-the-number-of-slices-for-a-search-slicing-point-in-time-query/378798/4 "2025-06-10T12:36:10Z")

</div>

My guess is that the number of slices depends mainly on the number of documents (d) in the index (not the number of documents of the query) and must be a multiple of the number of shards (s) in the index. Both can be obtained by a [count request](https://www.elastic.co/guide/en/elasticsearch/client/java-rest/current/java-rest-high-count.html).  
In that case the formula is: `slices = s * (roundUp(d / 10_000) / s)`