7.16.15. json_extract — Groonga v16.0.8 documentation

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# 7.16.15. `json_extract`

Added in version 16.0.6.

Note

This is an experimental feature. Currently, this feature is still not stable.

## 7.16.15.1. Summary

`json_extract` extracts values from a JSON by a JSONPath expression.

The extracted values keep their JSON types. For example, a string in JSON is extracted as a text and an integer in JSON is extracted as an integer. So you can use `json_extract` for both full text search against strings and range search against numbers.

`json_extract` is often used in combination with the filter option of select. For example, you can combine `json_extract` with between to do a range search against values that are stored in a JSON.

Note

`json_extract` requires the simdjson and jsoncons libraries. It isn’t available if Groonga is built without them.

## 7.16.15.2. Syntax

`json_extract` requires two parameters:

    json_extract(json, jsonpath)

## 7.16.15.3. Usage

Here are a schema definition and sample data to show usage. The `value` column uses the `JSON` type and stores nested arrays:

Execution example:

    table_create Data TABLE_NO_KEY
    # [[0,1337566253.89858,0.000355720520019531],true]
    column_create Data value COLUMN_SCALAR JSON
    # [[0,1337566253.89858,0.000355720520019531],true]
    load --table Data
    [
    {"value": "{\"value\": [[1, 10], [100]]}"},
    {"value": "{\"value\": [[2], [20, 200]]}"},
    {"value": "{\"value\": [[-1, -10], [-100]]}"}
    ]
    # [[0,1337566253.89858,0.000355720520019531],3]

The following example extracts all elements of the nested arrays by the `$.value[*][*]` JSONPath and selects the records that have a value between `10` and `20`:

Execution example:

    select Data --filter 'between(json_extract(value, "$.value[*][*]"), 10, 20)'
    # [
    #   [
    #     0,
    #     1337566253.89858,
    #     0.000355720520019531
    #   ],
    #   [
    #     [
    #       [
    #         2
    #       ],
    #       [
    #         [
    #           "_id",
    #           "UInt32"
    #         ],
    #         [
    #           "value",
    #           "JSON"
    #         ]
    #       ],
    #       [
    #         1,
    #         {
    #           "value": [
    #             [
    #               1,
    #               10
    #             ],
    #             [
    #               100
    #             ]
    #           ]
    #         }
    #       ],
    #       [
    #         2,
    #         {
    #           "value": [
    #             [
    #               2
    #             ],
    #             [
    #               20,
    #               200
    #             ]
    #           ]
    #         }
    #       ]
    #     ]
    #   ]
    # ]

The records whose extracted values are between `10` and `20` are selected even though the values are stored in nested arrays in JSON.

## 7.16.15.4. Parameters

There are two required parameters.

### 7.16.15.4.1. Required parameters

#### 7.16.15.4.1.1. `json`

`json` is the target JSON. It must be a parsed JSON, such as a value of a `JSON` typed column, or a JSON string.

`json_extract` reports an error if this parameter isn’t a parsed JSON nor a JSON string.

#### 7.16.15.4.1.2. `jsonpath`

`jsonpath` is a JSONPath expression that matches the values to extract.

A JSONPath expression begins with `$`, which means the root of the JSON value. For example, `$.value[*]` matches all elements of the `value` array, and `$.value[*][*]` matches all elements of nested arrays under `value`.

`json_extract` reports an error if this parameter isn’t a valid JSONPath string.

## 7.16.15.5. Return value

`json_extract` returns a vector that contains all values matched by the JSONPath expression. The extracted values keep their JSON types.

## 7.16.15.6. See also

- between

- ExtractorJSON

- select