dbt + StarRocks Performance Tuning

When to Use

• Incremental dbt models that run slowly due to poor partition filtering
• dbt DAG with wide fan-out causing excessive table rebuilds
• Need to run ANALYZE TABLE after dbt model refreshes
• Optimizing join order and query plans for complex dbt models
• Tuning thread count and model concurrency for large dbt projects

---

Partition-Aware Incremental Filters

The most impactful optimization: ensure incremental models only scan new partitions.

-- BAD: scans entire source table even in incremental mode
{{ config(
    materialized='incremental',
    incremental_strategy='append',
    partition_by={"field": "created_at", "data_type": "date", "granularity": "day"}
) }}

SELECT * FROM {{ source('raw', 'events') }}
{% if is_incremental() %}
WHERE event_ts > (SELECT MAX(event_ts) FROM {{ this }})
{% endif %}

The MAX(event_ts) subquery scans this — fine for small tables but expensive for billions of rows.

-- GOOD: use partition column for both filter and watermark
{{ config(
    materialized='incremental',
    incremental_strategy='insert_overwrite',
    partition_by={"field": "event_date", "data_type": "date", "granularity": "day"}
) }}

{% set lookback_days = 3 %}

SELECT
    DATE(event_ts) AS event_date,
    user_id,
    event_type,
    event_ts
FROM {{ source('raw', 'events') }}

{% if is_incremental() %}
-- Reprocess last N days to handle late-arriving data
WHERE DATE(event_ts) >= DATE_SUB(CURDATE(), INTERVAL {{ lookback_days }} DAY)
{% endif %}

With insert_overwrite, dbt replaces only the matching partitions — no full scan of this.

---

Late-Arriving Data Window

Balance completeness vs performance:

{% set incremental_lookback_days = var('lookback_days', 3) %}

{% if is_incremental() %}
WHERE DATE(created_at) >= DATE_SUB(
    -- Use a fixed reference point, not NOW(), for reproducibility
    DATE('{{ var("ds", modules.datetime.date.today().isoformat()) }}'),
    INTERVAL {{ incremental_lookback_days }} DAY
)
{% endif %}

Run with override:

dbt run --vars '{"lookback_days": 7, "ds": "2024-01-15"}'

---

ANALYZE TABLE via Post-Hook

Always refresh CBO statistics after materializing a table:

-- models/gold/orders_daily.sql
{{ config(
    materialized='table',
    post_hook=[
        "ANALYZE TABLE {{ this }} WITH ASYNC MODE",
    ]
) }}

SELECT ...

For incremental models with partition granularity:

{{ config(
    materialized='incremental',
    incremental_strategy='insert_overwrite',
    partition_by={"field": "dt", "data_type": "date", "granularity": "day"},
    post_hook=[
        -- Analyze only today's partition (much faster than full table)
        "ANALYZE TABLE {{ this }} PARTITION (p{{ run_started_at.strftime('%Y%m%d') }}) WITH ASYNC MODE",
    ]
) }}

Bulk ANALYZE in post-hook for large projects:

# dbt_project.yml
models:
  my_project:
    gold:
      +post-hook: "ANALYZE TABLE {{ this }} WITH ASYNC MODE"

---

Query Hints in dbt Models

Embed StarRocks query hints directly in model SQL for complex join optimization:

-- models/gold/revenue_report.sql
{{ config(materialized='table') }}

-- Hint: force join order (orders first, then products)
SELECT /*+ LEADING(o p c) JOIN_METHOD(o, p, BROADCAST) */
    p.category,
    c.region,
    COUNT(*) AS order_count,
    SUM(o.amount) AS revenue
FROM {{ ref('orders') }} o
JOIN {{ ref('dim_products') }} p USING (product_id)
JOIN {{ ref('dim_customers') }} c USING (customer_id)
WHERE o.dt = CURDATE()
GROUP BY p.category, c.region

---

Pre-Hook: Ensure Partition Exists

For models that INSERT OVERWRITE into manually managed partitions:

{{ config(
    materialized='incremental',
    incremental_strategy='insert_overwrite',
    pre_hook=[
        """
        ALTER TABLE {{ this }}
        ADD PARTITION IF NOT EXISTS p{{ run_started_at.strftime('%Y%m%d') }}
        VALUES [("{{ run_started_at.strftime('%Y-%m-%d') }}"),
                ("{{ (run_started_at + modules.datetime.timedelta(days=1)).strftime('%Y-%m-%d') }}"))
        """
    ]
) }}

---

Materialized View as dbt Model

Create a StarRocks async MV using a dbt custom materialization or post-hook:

-- Approach 1: Create MV in a post-hook on the base table
{{ config(
    materialized='table',
    post_hook=[
        """
        CREATE MATERIALIZED VIEW IF NOT EXISTS {{ this }}_mv
        DISTRIBUTED BY HASH(region) BUCKETS 8
        REFRESH ASYNC EVERY (INTERVAL 1 HOUR)
        AS SELECT region, COUNT(*) AS orders, SUM(amount) AS revenue
           FROM {{ this }}
           GROUP BY region
        """
    ]
) }}

---

Thread and Concurrency Tuning

profiles.yml Thread Config

starrocks_project:
  outputs:
    prod:
      type: starrocks
      threads: 8           # concurrent model builds (default: 1)
      # ...

Which Models Can Run in Parallel

dbt parallelizes models with no dependencies between them. Ensure your DAG is as wide as possible:

staging/stg_orders    ─┐
staging/stg_customers ─┼──► silver/orders (sequential join)
staging/stg_products  ─┘

silver/orders_by_region ─┐
silver/orders_by_product ─┼──► gold/revenue_report
silver/customer_segments ─┘

Avoid chains where each model depends on the previous — this prevents parallelism.

---

Model Selection for Minimal Rebuilds

# Only run models that changed + their downstream dependents
dbt run --select state:modified+

# Run only changed models, no downstream
dbt run --select state:modified

# Run only a specific model and its upstream dependencies
dbt run --select +orders

# Run a specific tag group
dbt run --select tag:daily

# Exclude expensive models from CI
dbt run --exclude tag:expensive

---

var() for Environment-Specific Config

{{ config(
    materialized='incremental',
    incremental_strategy='insert_overwrite',
    partition_by={
        "field": "dt",
        "data_type": "date",
        "granularity": var('partition_granularity', 'day')
    },
    properties={
        "replication_num": var('replication_num', '3')
    }
) }}

# dbt_project.yml
vars:
  partition_granularity: "day"
  replication_num: "3"    # override to "1" in dev

dbt run --vars '{"replication_num": "1"}' --target dev

---

Materialization Choice vs Performance

Model Type	Materialization	Rebuild Frequency	Performance
Staging (raw cleanup)	table	Daily	Full rebuild is cheap
Silver (CDC upsert)	incremental (unique_key)	Continuous	Only processes delta
Intermediate heavy joins	table	Daily	Avoid ephemeral for >100M rows
Gold partitions	incremental (insert_overwrite)	Daily	Replace partitions, not full table
Real-time metrics	MV via post-hook	Auto (async)	Near-real-time without DAG run
Rarely queried reports	view	On query	No storage cost

---

Profiling Slow Models

# Show timing for each model
dbt run --select orders_daily --log-level debug 2>&1 | grep "Completed"

# Use dbt artifacts for timing analysis
cat target/run_results.json | python3 -c "
import json, sys
r = json.load(sys.stdin)
for n in sorted(r['results'], key=lambda x: x.get('execution_time', 0), reverse=True)[:10]:
    print(f\"{n['execution_time']:.1f}s  {n['unique_id']}\")
"

---

Anti-Patterns

1. incremental_strategy='append' on a growing table without watermark — re-runs append all historical rows repeatedly; always add an is_incremental() filter.
2. MAX(event_ts) FROM {{ this }} for watermark on billion-row tables — scans the entire previous model; use partition column bounds instead.
3. threads: 1 — serial execution for large dbt projects can take hours; set to 4-16 based on BE count.
4. No post-hook ANALYZE — CBO uses stale stats after model rebuild, producing bad plans for downstream queries; always ANALYZE after table materialization.
5. Using view for heavy aggregations — view recomputes the aggregation on every BI query; materialize as table or MV.
6. on_schema_change='sync_all_columns' on large tables — triggers full table rebuild every time a column is added; use append_new_columns instead.

---

References

• dbt-starrocks incremental: github.com/StarRocks/starrocks/tree/main/contrib/dbt-connector
• ANALYZE TABLE: docs.starrocks.io/docs/sql-reference/sql-statements/data-definition/ANALYZE_TABLE/
• dbt model selection: docs.getdbt.com/reference/node-selection/syntax
• Related skills: [[dbt-starrocks-models]], [[starrocks-cbo]], [[starrocks-query-optimizer]], [[dbt-core]]