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# 7.3.11. `column_rename`

## 7.3.11.1. Summary

`column_rename` command renames a column.

It is a light operation. It just changes a relationship between name and the column object. It doesn't copy column values.

It is a dangerous operation. You must stop all operations including read operations while you run `column_rename`. If the following case is occurred, Groonga process may be crashed:

> - Starts an operation (like `select`) that accesses the column to be renamed by the current column name. The current column name is called as `the old column name` in the below because the column name is renamed.
> - Runs `column_rename`. The `select` is still running.
> - The `select` accesses the column to be renamed by the old column name. But the `select` can't find the column by the old name because the column has been renamed to the new column name. It may crash the Groonga process.

## 7.3.11.2. Syntax

`column_rename` command takes three parameters. All parameters are required:

    column_rename table name new_name

## 7.3.11.3. Usage

Here is a simple example of `column_rename` command.

Execution example:

    table_create Users TABLE_PAT_KEY ShortText
    # [[0, 1337566253.89858, 0.000355720520019531], true]
    column_create Users score COLUMN_SCALAR Int32
    # [[0, 1337566253.89858, 0.000355720520019531], true]
    load --table Users
    [
    {"_key": "Alice",  "score": 2},
    {"_key": "Bob",    "score": 0},
    {"_key": "Carlos", "score": -1}
    ]
    # [[0, 1337566253.89858, 0.000355720520019531], 3]
    column_rename Users score point
    # [[0, 1337566253.89858, 0.000355720520019531], true]
    column_list Users
    # [
    #   [
    #     0,
    #     1337566253.89858,
    #     0.000355720520019531
    #   ],
    #   [
    #     [
    #       [
    #         "id",
    #         "UInt32"
    #       ],
    #       [
    #         "name",
    #         "ShortText"
    #       ],
    #       [
    #         "path",
    #         "ShortText"
    #       ],
    #       [
    #         "type",
    #         "ShortText"
    #       ],
    #       [
    #         "flags",
    #         "ShortText"
    #       ],
    #       [
    #         "domain",
    #         "ShortText"
    #       ],
    #       [
    #         "range",
    #         "ShortText"
    #       ],
    #       [
    #         "source",
    #         "ShortText"
    #       ]
    #     ],
    #     [
    #       256,
    #       "_key",
    #       "",
    #       "",
    #       "COLUMN_SCALAR",
    #       "Users",
    #       "ShortText",
    #       []
    #     ],
    #     [
    #       257,
    #       "point",
    #       "/tmp/groonga-databases/commands_column_rename.0000101",
    #       "fix",
    #       "COLUMN_SCALAR|PERSISTENT",
    #       "Users",
    #       "Int32",
    #       []
    #     ]
    #   ]
    # ]
    select Users
    # [
    #   [
    #     0,
    #     1337566253.89858,
    #     0.000355720520019531
    #   ],
    #   [
    #     [
    #       [
    #         3
    #       ],
    #       [
    #         [
    #           "_id",
    #           "UInt32"
    #         ],
    #         [
    #           "_key",
    #           "ShortText"
    #         ],
    #         [
    #           "point",
    #           "Int32"
    #         ]
    #       ],
    #       [
    #         1,
    #         "Alice",
    #         2
    #       ],
    #       [
    #         2,
    #         "Bob",
    #         0
    #       ],
    #       [
    #         3,
    #         "Carlos",
    #         -1
    #       ]
    #     ]
    #   ]
    # ]

## 7.3.11.4. Parameters

This section describes parameters of `column_rename`.

### 7.3.11.4.1. Required parameters

All parameters are required.

#### 7.3.11.4.1.1. `table`

It specifies the name of table that has the column to be renamed.

#### 7.3.11.4.1.2. `name`

It specifies the column name to be renamed.

#### 7.3.11.4.1.3. `new_name`

It specifies the new column name.

## 7.3.11.5. Return value

    [HEADER, SUCCEEDED_OR_NOT]

`HEADER`

> See Output format about `HEADER`.

`SUCCEEDED_OR_NOT`

> It is `true` on success, `false` otherwise.