从键中删除字段

默认情况下，RDI 会将字段添加到目标中的哈希或 JSON 对象 database 的 database 中。 以下示例显示了如何使用remove_field转型。

删除单个字段

第一个示例从数据中删除单个字段。 这source部分选择employee的chinookdatabase（可选的dbfield 对应于sources.<source-name>.connection.database字段定义于config.yaml).

在transform部分、remove_field转换会删除hiredate田。

这outputsection 指定hash作为data_type写入目标，该 覆盖target_data_type定义于config.yaml.此外，output.with.keysection 指定表单的自定义键格式emp:<employeeid>. 请注意，您在transform部分不适用于 Key 计算中的output部分。

完整示例如下所示：

source:
  db: chinook
  table: employee
transform:
  - uses: remove_field
    with:
      field: hiredate
output:
  - uses: redis.write
    with:
      connection: target
      data_type: hash
      key:
        expression: concat(['emp:', employeeid])
        language: jmespath

If you queried the generated target data from the default transformation using redis-cli, you would see something like the following:

> hgetall emp:8
 1) "employeeid"
 2) "8"
 3) "lastname"
 4) "Callahan"
 5) "firstname"
 6) "Laura"
 7) "title"
 8) "IT Staff"
 9) "reportsto"
10) "6"
11) "birthdate"
12) "-62467200000000"
13) "hiredate"
14) "1078358400000000"
15) "address"
16) "923 7 ST NW"
.
.

Using the job file above, the data omits the hiredate field:

 > hgetall emp:8
 1) "employeeid"
 2) "8"
 3) "lastname"
 4) "Callahan"
 5) "firstname"
 6) "Laura"
 7) "title"
 8) "IT Staff"
 9) "reportsto"
10) "6"
11) "birthdate"
12) "-62467200000000"
13) "address"
14) "923 7 ST NW"
.
.

Remove multiple fields

The remove_field transformation can also remove multiple fields at the same time if you specify them under a fields subsection. The example below is similar to the previous one but also removes the birthdate field:

source:
  db: chinook
  table: employee
transform:
  - uses: remove_field
    with:
      fields:
        - field: hiredate
        - field: birthdate
output:
  - uses: redis.write
    with:
      connection: target
      data_type: hash
      key:
        expression: concat(['emp:', employeeid])
        language: jmespath

If you query the data, you can see that it also omits the birthdate field:

> hgetall emp:8
 1) "employeeid"
 2) "8"
 3) "lastname"
 4) "Callahan"
 5) "firstname"
 6) "Laura"
 7) "title"
 8) "IT Staff"
 9) "reportsto"
10) "6"
11) "address"
12) "923 7 ST NW"
.
.

Using remove_field with add_field

The remove_field transformation is very useful in combination with add_field. For example, if you use add_field to concatenate a person's first and last names, you may not need separate firstname and lastname fields, so you can use remove_field to omit them. See Using add_field with remove_field for an example of how to do this.

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