template_record

Modify records using a Go template and apply changes by using the PostgreSQL driver functions. This transformer provides a way to implement custom transformation logic.

Parameters

Name	Description	Default	Required	Supported DB types
columns	A list of columns to be affected by the template. The list of columns will be checked for constraint violations.		No	any
template	A Go template string		Yes	-
validate	Validate the template result via PostgreSQL driver decoding procedure. Throws an error if a custom type does not have an encode-decoder implementation.	false	No	-

Description

TemplateRecord uses Go templates to change data. However, while the Template transformer operates with a single column and automatically applies results, the TemplateRecord transformer can make changes to a set of columns in the string, and using driver functions .SetValue or .SetRawValue is mandatory to do that.

With the TemplateRecord 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 TemplateRecord transformer. For more information about available custom template functions, see Custom functions.

Template functions

Function	Description	Signature
.GetColumnType	Returns a string with the column type.	.GetColumnType(name string) (typeName 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)
.SetColumnValue	Sets a new value of a specific data type to the column. The value assigned must be compatible with the PostgreSQL data type of the column. For example, it is allowed to assign an int value to an INTEGER column, but you cannot assign a float value to a timestamptz column.	SetColumnValue(name string, v any) (bool, error)
.SetRawColumnValue	Sets a new raw value for a column, inheriting the column's existing data type, without performing data type validation. This can lead to errors when restoring the dump if the assigned value is not compatible with the column type. To ensure compatibility, consider using the .DecodeValueByColumn function followed by .SetColumnValue, for example, {{ "13" | .DecodeValueByColumn "items_amount" | .SetColumnValue "items_amount" }}.	.SetRawColumnValue(name string, value 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: Generate a random created_at and updated_at dates

Below you can see the table structure:

The goal is to modify the "created_at" and "updated_at" columns based on the following rules:

• Do not change the value if the created_at is Null.
• If the created_at is not Null, generate the current time and use it as the minimum threshold for randomly generating the updated_at value.
• Assign all generated values using the .SetColumnValue function.

Template transformer example

- name: "TemplateRecord"
  params:
    columns:
      - "created_at"
      - "updated_at"
    template: >
      {{ $val := .GetColumnValue "created_at" }}
      {{ if isNotNull $val }}
          {{ $createdAtValue := now }}
          {{ $maxUpdatedDate := date_modify "24h" $createdAtValue }}
          {{ $updatedAtValue := randomDate $createdAtValue $maxUpdatedDate }}
          {{ .SetColumnValue "created_at" $createdAtValue }}
          {{ .SetColumnValue "updated_at" $updatedAtValue }}
      {{ end }}
    validate: true

Expected result:

column name	original value	transformed
created_at	2021-01-20 07:01:00.513325+00	2023-12-17 19:37:29.910054Z
updated_at	2021-08-09 21:27:00.513325+00	2023-12-18 10:05:25.828498Z