Parameters templating¶

Description¶

It is allowed to generate parameter values from templates. It is useful when you don't want to write values manually, but instead want to generate and initialize them dynamically.

Here you can find the list of template functions that can be used in the template Custom functions.

You can encode and decode objects using the driver function bellow.

Template functions¶

Function	Description	Signature
`.GetColumnType`	Returns a string with the column type.	`.GetColumnType(name string) (typeName string, 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)`
`.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)`
`.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)`

Warning

If column parameter is not linked to column parameter, then functions .DecodeValue and .EncodeValue will return an error. You can use .DecodeValueByType and .EncodeValueByType or .DecodeValueByColumn and .EncodeValueByColumn instead.

Example¶

In the example below, the min and max values for the birth_date column are generated dynamically using the now template function. The value returns the current date and time. The tsModify function is then used to subtract 30 (and 18) years. But because the parameter type is mapped on column parameter type, the EncodeValue function is used to encode the value into the column type.

For example, if we have the now date as 2021-01-01, the dynamically calculated min value will be 1994-01-01 and the max value will be 2006-01-01.

CREATE TABLE account
(
    id         SERIAL PRIMARY KEY,
    gender     VARCHAR(1) NOT NULL,
    email      TEXT       NOT NULL NOT NULL UNIQUE,
    first_name TEXT       NOT NULL,
    last_name  TEXT       NOT NULL,
    birth_date DATE,
    created_at TIMESTAMP  NOT NULL DEFAULT NOW()
);

INSERT INTO account (first_name, gender, last_name, birth_date, email)
VALUES ('John', 'M', 'Smith', '1980-01-01', 'john.smith@gmail.com');

- schema: "public"
  name: "account"
  transformers:
    - name: "RandomDate"
      params:
        column: "birth_date"
        min: '{{ now | tsModify "-30 years" | .EncodeValue }}' # 1994
        max: '{{ now | tsModify "-18 years" | .EncodeValue }}' # 2006

Result

Column	OriginalValue	TransformedValue
birth_date	1980-01-01	1995-09-06