Template

Execute a Go template and automatically apply the result to a specified column.

Parameters¶

Name	Description	Default	Required	Supported DB types
column	The name of the column to be affected		Yes	any
template	A Go template string		Yes	-
validate	Validates the template result using the PostgreSQL driver decoding procedure. Throws an error if a custom type does not have an encode-decoder implementation.	false	No	-

Description¶

The Template transformer executes Go templates and automatically applies the template result to a specified column. Go template system is designed to be extensible, enabling developers to access data objects and incorporate custom functions programmatically. For more information, you can refer to the official Go Template documentation.

With the Template transformer, you can implement complicated transformation logic using basic or custom template functions. Below you can get familiar with the basic template functions for the Template transformer. For more information about available custom template functions, see Custom functions.

Warning

Pay attention to the whitespaces in templates. Use dash-wrapped - brackets {{- -}} for trimming the spaces. For example, the value "2023-12-19" is not the same as " 2023-12-19 " and it may throw an error when restoring.

Template functions¶

Function	Description	Signature
`.GetColumnType`	Returns a string with the column type.	`.GetColumnType(name string) (typeName string, err error)`
`.GetValue`	Returns the column value for column assigned in the `column` parameter, encoded by the PostgreSQL driver into any type along with any associated error. Supported types include `int`, `float`, `time`, `string`, `bool`, as well as `slice` or `map` of any type.	`.GetValue() (value any, err error)`
`.GetRawValue`	Returns a raw value as a string for column assigned in the `column` parameter.	`.GetRawColumnValue(name string) (value string, err error)`
`.GetColumnValue`	Returns an encoded value for a specified column or throws an error. A value can be any of `int`, `float`, `time`, `string`, `bool`, or `slice` or `map`.	`.GetColumnValue(name string) (value any, err error)`
`.GetRawColumnValue`	Returns a raw value for a specified column as a string or throws an error	`.GetRawColumnValue(name string) (value string, err error)`
`.EncodeValue`	Encodes a value of any type into its string representation using the type assigned to the table column specified in the `column` parameter. Encoding is performed through the PostgreSQL driver. Throws an error if types are incompatible.	`.EncodeValue(value any) (res any, err error)`
`.DecodeValue`	Decodes a value from its raw string representation to a Golang type using the data type assigned to the table column specified in the `column` parameter. Decoding is performed through the PostgreSQL driver. Throws an error if types are incompatible.	`.DecodeValueByColumn(value any) (res any, err error)`
`.EncodeValueByColumn`	Encodes a value of any type into its raw string representation using the specified column name. Encoding is performed through the PostgreSQL driver. Throws an error if types are incompatible.	`.EncodeValueByColumn(name string, value any) (res any, err error)`
`.DecodeValueByColumn`	Decodes a value from its raw string representation to a Golang type using the specified column name. Decoding is performed through the PostgreSQL driver. Throws an error if types are incompatible.	`.DecodeValueByColumn(name string, value any) (res any, err error)`
`.EncodeValueByType`	Encodes a value of any type into its string representation using the specified type name. Encoding is performed through the PostgreSQL driver. Throws an error if types are incompatible.	`.EncodeValueByType(name string, value any) (res any, err error)`
`.DecodeValueByType`	Decodes a value from its raw string representation to a Golang type using the specified type name. Decoding is performed through the PostgreSQL driver. Throws an error if types are incompatible.	`.DecodeValueByType(name string, value any) (res any, err error)`

Example: Update the `firstname` column¶

Below you can see the table structure:

Change rule¶

The goal is to modify the firstname column based on the following conditions:

If the current value of the firstname column is equal to Terri, replace it with Mary.
For all other cases, generate a random name and append Jr.

Using a template function¶

To generate random names, you can use the fakerFirstName template function, which is designed to create synthetic names.

Template transformer example

- schema: "humanresources"
  name: "employee"
  transformation:
    - name: "Template"
      params:
        column: "firstname"
        template: >
          {{- if eq .GetValue "Terri" -}}
            Mary
          {{- else -}}
            {{- fakerFirstName -}} Jr
          {{- end -}}

        validate: true

Expected result:

Value = TerryValue != Terri

column name	original value	transformed
firstname	Terri	Mary

column name	original value	transformed
firstname	Ken Jr	Mike