Strategies#

Strategies determine how model results are updated when the pipeline runs.

Available Strategies#

Replace (Default)#

Drops and recreates the table on each run:

@model(name="daily_snapshot", materialise="table", strategy="replace")
def daily_snapshot(source: ibis.Table) -> ibis.Table:
    return source

Best for:

• Full refreshes
• Small to medium tables
• Data that doesn’t need history

Append#

Adds new rows without removing existing data:

@model(name="event_log", materialise="table", strategy="append")
def event_log(new_events: ibis.Table) -> ibis.Table:
    return new_events

Best for:

• Event logs
• Time-series data
• Audit trails

Merge by Key#

Updates existing rows and inserts new ones based on primary key:

@model(
    name="customers",
    materialise="table",
    strategy="merge_by_key",
    primary_key=["customer_id"]
)
def customers(raw_customers: ibis.Table) -> ibis.Table:
    return raw_customers

Best for:

• Dimension tables
• Data with natural keys
• Incremental updates

SCD Type 2#

Slowly Changing Dimension Type 2 – maintains full history of changes by versioning rows:

@model(
    name="customer_history",
    materialise="table",
    strategy="scd_type_2",
    primary_key=["customer_id"]
)
def customer_history(customers: ibis.Table) -> ibis.Table:
    return customers

Interlace automatically manages:

• valid_from – timestamp when the row became current
• valid_to – timestamp when the row was superseded (NULL for current)
• is_current – boolean flag for the active version

Best for:

• Audit-sensitive dimensions (customer status changes, pricing history)
• Regulatory compliance requiring full change history
• Analytics that need point-in-time lookups

None#

No persistence – the model runs but nothing is written to the database:

@model(name="send_alerts", materialise="none", strategy="none")
def send_alerts(failed_checks: ibis.Table) -> None:
    for row in failed_checks.execute().to_dict(orient="records"):
        send_slack_notification(row)

Best for:

• Side-effect models (notifications, API calls)
• Models that write to external systems

Choosing a Strategy#