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Merge pull request #42 from opensearch-project/agg_intro_edit 

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docs/opensearch/aggregations.md
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@ -16,13 +16,13 @@ OpenSearch can perform aggregations on massive datasets in milliseconds. Compare
## Aggregations on text fields ## Aggregations on text fields
By default, OpenSearch doesn't support aggregations on a text field. By default, OpenSearch doesn't support aggregations on a text field. Because text fields are tokenized, an aggregation on a text field has to reverse the tokenization process back to its original string and then formulate an aggregation based on that. This kind of an operation consumes significant memory and degrades cluster performance.
Because text fields are tokenized, an aggregation on a text field has to reverse the tokenization process back to its original string and then formulate an aggregation based on that. Such an operation consumes significant memory and degrades cluster performance.
While you can enable aggregations on text fields by setting the `fielddata` parameter to `true` in the mapping, the aggregations are still based on the tokenized words and not on the raw text. While you can enable aggregations on text fields by setting the `fielddata` parameter to `true` in the mapping, the aggregations are still based on the tokenized words and not on the raw text.
We recommend keeping a raw version of the text field as a `keyword` field that you can aggregate on. We recommend keeping a raw version of the text field as a `keyword` field that you can aggregate on.
In this case, you can perform aggregations on the `title.raw` field, instead of the `title` field:
In this case, you can perform aggregations on the `title.raw` field, instead of on the `title` field:
```json ```json
PUT movies PUT movies
@ -61,15 +61,13 @@ GET _search
If you’re only interested in the aggregation result and not in the results of the query, set `size` to 0. If you’re only interested in the aggregation result and not in the results of the query, set `size` to 0.
In the `aggs` property (you can use `aggregations` if you want), you can define any number of aggregations. In the `aggs` property (you can use `aggregations` if you want), you can define any number of aggregations. Each aggregation is defined by its name and one of the types of aggregations that OpenSearch supports.
Each aggregation is defined by its name and one of the types of aggregations that OpenSearch supports.
The name of the aggregation helps you to distinguish between different aggregations in the response. The name of the aggregation helps you to distinguish between different aggregations in the response. The `AGG_TYPE` property is where you specify the type of aggregation.
The `AGG_TYPE` property is where you specify the type of aggregation.
## Sample aggregation ## Sample aggregation
This section uses the OpenSearch Dashboards sample e-commerce data and web log data. To add the sample data, log in to OpenSearch Dashboards, choose **Home** and **Try our sample data**. For **Sample eCommerce orders** and **Sample web logs**, choose **Add data**. This section uses the OpenSearch Dashboards sample ecommerce data and web log data. To add the sample data, log in to OpenSearch Dashboards, choose **Home**, and then choose **Try our sample data**. For **Sample eCommerce orders** and **Sample web logs**, choose **Add data**.
### avg ### avg
@ -129,7 +127,7 @@ There are three main types of aggregations:
## Nested aggregations ## Nested aggregations
Aggregations within aggregations are called nested or sub aggregations. Aggregations within aggregations are called nested or subaggregations.
Metric aggregations produce simple results and can't contain nested aggregations. Metric aggregations produce simple results and can't contain nested aggregations.