# Customising Macros in DBT

**URL:** <https://discourse.getdbt.com/t/customising-macros-in-dbt/5467>\
**Category:** Help\
**Created:** [December 2, 2022, 2:27pm UTC](https://discourse.getdbt.com/t/customising-macros-in-dbt/5467 "2022-12-02T14:27:04Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Andy2](https://avatars.discourse-cdn.com/v4/letter/a/b9bd4f/32.png) [@Andy2](https://discourse.getdbt.com/u/Andy2)\
**Post date:** [December 2, 2022, 2:27pm UTC](https://discourse.getdbt.com/t/customising-macros-in-dbt/5467/1 "2022-12-02T14:27:04Z")

</div>

Hi, Iam a newbie to DBT here and considering the use of macros to customise the snapshot handling of DBT.  
Specifically ,Iam trying to replace the names of the default meta columns and then I end up getting errors when i run the snapshot command on the model for the second time.  
The error message i get is : Snapshot target has (“x”, “y”, “z”) but not (“dbt\_scd\_id”, “dbt\_valid\_from”, “dbt\_valid\_to”) - is it an unmigrated previous version archive?  
Could you help me figure out what the mistake iam doing here ?  
Thanks in advance.  
Here are the codes that I use

– Person Snapshot  
{% snapshot person\_snapshot %}

{{  
config(

```
  unique_key='ID',
  strategy='check' ,
    target_schema='myschema',
  check_cols='all',
     )

```

}}  
– Overriding Macros  
{% macro build\_snapshot\_table(strategy, sql) %}

```
select *,
    {{ strategy.scd_id }} as scd_id,
    {{ strategy.updated_at }} as updated_at,
     {{ strategy.updated_at }} as valid_from,
    
    nullif({{ strategy.updated_at }}, {{ strategy.updated_at }}) as valid_to,
    Case When ({{ strategy.updated_at }}= {{ strategy.updated_at }})
    Then 1 
    Else 0 
    End
    as aktiv
from (
    {{ sql }}
) sbq

```

{% endmacro %}

– Overriding Macro build staging tables snapshot  
{% macro snapshot\_staging\_table(strategy, source\_sql, target\_relation) %}

```
with snapshot_query as (

    {{ source_sql }}

),

snapshotted_data as (

    select *,
        {{ strategy.unique_key }} as dbt_unique_key

    from {{ target_relation }}
    where valid_to is null

),

insertions_source_data as (

    select
        *,
        {{ strategy.unique_key }} as dbt_unique_key,
        {{ strategy.updated_at }} as dbt_updated_at,
         {{ strategy.updated_at }} as dbt_valid_from,
        
        nullif({{ strategy.updated_at }}, {{ strategy.updated_at }}) as dbt_valid_to,
        {{ strategy.scd_id }} as dbt_scd_id

    from snapshot_query
),

updates_source_data as (

    select
        *,
        {{ strategy.unique_key }} as dbt_unique_key,
        {{ strategy.updated_at }} as dbt_updated_at,
        {{ strategy.updated_at }} as dbt_valid_from,
        
        {{ strategy.updated_at }} as dbt_valid_to
       

    from snapshot_query
),

{%- if strategy.invalidate_hard_deletes %}

deletes_source_data as (

    select 
        *,
        {{ strategy.unique_key }} as dbt_unique_key
    from snapshot_query
),
{% endif %}

insertions as (

    select
        'insert' as dbt_change_type,
        source_data.*

    from insertions_source_data as source_data
    left outer join snapshotted_data on snapshotted_data.scd_id = source_data.dbt_unique_key
    where snapshotted_data.scd_id is null
       or (
            snapshotted_data.scd_id is not null
        and (
            {{ strategy.row_changed }}
        )
    )

),

updates as (

    select
        'update' as dbt_change_type,
        source_data.*,
        snapshotted_data.dbt_scd_id

    from updates_source_data as source_data
    join snapshotted_data on snapshotted_data.scd_id = source_data.dbt_unique_key
    where (
        {{ strategy.row_changed }}
    )
)

{%- if strategy.invalidate_hard_deletes -%}
,

deletes as (

    select
        'delete' as dbt_change_type,
        source_data.*,
        {{ snapshot_get_time() }} as dbt_valid_from,
        {{ snapshot_get_time() }} as dbt_updated_at,
        {{ snapshot_get_time() }} as dbt_valid_to,
        snapshotted_data.dbt_scd_id

    from snapshotted_data
    left join deletes_source_data as source_data on snapshotted_data.scd_id = source_data.dbt_unique_key
    where source_data.dbt_unique_key is null
)
{%- endif %}

select * from insertions
union all
select * from updates
{%- if strategy.invalidate_hard_deletes %}
union all
select * from deletes
{%- endif %}

```

{% endmacro %}

select ID,name,CityID  
from {{ ref(‘vw\_person’) }}

{% endsnapshot %}

---

<div class="post-metadata">

**Author:** ![jeffsk](https://sea2.discourse-cdn.com/flex020/user_avatar/discourse.getdbt.com/jeffsk/32/1250_2.png) [@jeffsk](https://discourse.getdbt.com/u/jeffsk)\
**Post date:** [December 7, 2022, 2:49pm UTC](https://discourse.getdbt.com/t/customising-macros-in-dbt/5467/2 "2022-12-07T14:49:35Z")

</div>

A more sustainable way to do this which will not cause problems through upgrades, etc. is to just let dbt Snapshot do its thing… then if you want to change the column names, put a view after the snapshot which re-names the columns. You can hide the original model from non-developer people in a stg schema and only expose the model with the desired column names to your users.