dbt-gp-delta 0.13.0

Greenplum adapter for dbt with exchange_partition incremental strategy

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dbt-gp-delta

The dbt-gp-delta package contains the code enabling dbt to work with Greenplum. It is based on dbt-gp - a Greenplum adapter built on top of the postgres-adapter - and extends it with the exchange_partition incremental strategy without modifying any of the original functionality.

Installation

Easiest way to start use dbt-greenplum is to install it using pip pip install dbt-gp-delta==<version>

Where <version> is same as your dbt version

Available versions:

• 0.13.0

exchange_partition incremental strategy

The exchange_partition strategy implements atomic, partition-level incremental loads using Greenplum's EXCHANGE PARTITION DDL operation. Instead of inserting rows into the live table, it builds a separate swap table for each affected partition period and atomically replaces the partition via a metadata-only operation — no physical data movement occurs.

How it works

Overwrite mode (default, exchange_merge_partitions=false)

Start model
    │
    ▼
if target does not exist:
    └── CREATE TABLE target  (columns from model contract in schema.yml,
    │                          PARTITION BY RANGE, EVERY '1 day|month')
    │
    ├── if target exists but is NOT partitioned → compile-time error
    │
    ▼
dbt creates a temporary staging table with the model SQL result
    │   (standard dbt incremental mechanism, heap table in the session temp schema)
    ▼
for each period in DISTINCT(staging.partition_key):   ← only periods with data
    ├── ADD PARTITION (if missing)
    ├── CREATE swap table  (schema: exchange_stage_schema, same dist + storage as target)
    │           name: <exchange_stage_schema>.__swap_<model>_<YYYYMMDD>  (day)
    │           name: <exchange_stage_schema>.__swap_<model>_<YYYYMM>    (month)
    ├── INSERT  ← only staging rows for this period
    ├── EXCHANGE PARTITION  (atomic leaf replacement)
    └── DROP swap table
    │
    ▼
dbt drops the temporary staging table automatically (end of session)
ANALYZE target  (if exchange_analyze=true)

The target partition is fully replaced with data from the delta.

Merge mode (exchange_merge_partitions=true)

Start model
    │
    ▼
if target does not exist:
    └── CREATE TABLE target  (columns from model contract in schema.yml,
    │                          PARTITION BY RANGE, EVERY '1 day|month')
    │
    ├── if target exists but is NOT partitioned → compile-time error
    │
    ▼
dbt creates a temporary staging table with the model SQL result
    │   (standard dbt incremental mechanism, heap table in the session temp schema)
    ▼
for each period in DISTINCT(staging.partition_key):   ← only periods with data
    ├── ADD PARTITION (if missing)
    ├── CREATE swap table AS  (schema: exchange_stage_schema)
    │     SELECT ... FROM delta WHERE period = this_period        ← all delta rows
    │     UNION ALL
    │     SELECT ... FROM target WHERE period = this_period
    │       AND NOT EXISTS (SELECT 1 FROM delta WHERE merge_keys match)  ← target rows not in delta
    ├── EXCHANGE PARTITION
    └── DROP swap table
    │
    ▼
dbt drops the temporary staging table automatically (end of session)
ANALYZE target  (if exchange_analyze=true)

When merge_keys match, delta rows take priority — target rows whose key matches a delta row are dropped via NOT EXISTS. Target rows that are not present in the delta by key are preserved. Duplicates within the delta itself are not deduplicated automatically — if the delta contains multiple rows with the same merge_key, all of them will appear in the result. Deduplicate the delta in the model SQL if needed.

Required model config

Parameter	Type	Description
exchange_partition_key	string	Column used as the partition key. Must be castable to timestamptz.
exchange_stage_schema	string	Schema where staging and swap tables are created. Must exist in the database.
exchange_merge_partitions	bool	true — merge new rows with existing partition data (requires unique_key). false — fully overwrite affected partitions with staging data.
contract: enforced: true	—	Declared in schema.yml (not in config()). Column types are required because the target table is created via explicit DDL, not CTAS. The strategy raises a compile-time error if the contract is not enforced.

Optional model config

Parameter	Type	Default	Description
unique_key	string or list	—	Column(s) that uniquely identify a row. Required when exchange_merge_partitions=true.
exchange_partition_granularity	string	'day'	Partition period: 'day' or 'month'.
exchange_create_missing_partitions	bool	true	Automatically add missing partitions for new periods found in staging data.
exchange_allow_with_validation	bool	true	Use WITH VALIDATION during EXCHANGE PARTITION. Set to false for faster exchange when data correctness is guaranteed upstream.
exchange_analyze	bool	true	Run ANALYZE on the target table after all partitions are exchanged.
exchange_initial_partition_start_at	string YYYY-MM-DD	Jan 1 of current year	Start date of the initial partition created on the first run. Can also be set via dbt var exchange_initial_partition_start_at.
exchange_initial_partition_end_at	string YYYY-MM-DD	start + 1 period	End date of the initial partition range. If omitted, exactly one partition is created. Can also be set via dbt var exchange_initial_partition_end_at.
distributed_by	string	RANDOMLY	Distribution key(s) for the target table, e.g. 'id' or 'tenant_id, id'.
appendoptimized	bool	—	Create an append-optimised (AO) table.
orientation	string	—	'column' or 'row'. Applies only when appendoptimized=true.
compresstype	string	—	Compression algorithm, e.g. 'ZSTD', 'ZLIB'. Applies only when appendoptimized=true.
compresslevel	int	—	Compression level (0–9). Applies only when appendoptimized=true.
blocksize	int	—	Block size in bytes. Applies only when appendoptimized=true.

Overwrite mode example

Every run fully replaces all partitions that appear in the new data. Useful when the source already delivers a clean, complete snapshot for each period.

{{
    config(
        materialized='incremental',
        incremental_strategy='exchange_partition',

        exchange_partition_key='transaction_date',
        exchange_partition_granularity='day',
        exchange_stage_schema='stage',
        exchange_merge_partitions=false,

        exchange_initial_partition_start_at='2024-01-01',
        exchange_initial_partition_end_at='2024-02-01',

        distributed_by='id',
        appendoptimized=true,
        orientation='column',
        compresstype='ZSTD',
        compresslevel=1
    )
}}

select
    id,
    transaction_date,
    amount
from {{ source('raw', 'transactions') }}
{% if is_incremental() %}
where transaction_date >= current_date - interval '3 days'
{% endif %}

schema.yml for this model must declare column types:

models:
  - name: transactions
    config:
      contract:
        enforced: true
    columns:
      - name: id
        data_type: bigint
      - name: transaction_date
        data_type: date
      - name: amount
        data_type: numeric(18,2)

Merge mode example

New rows are merged with existing partition data. Rows matched by unique_key are replaced by the incoming version; unmatched existing rows are preserved.

{{
    config(
        materialized='incremental',
        incremental_strategy='exchange_partition',

        exchange_partition_key='event_date',
        exchange_partition_granularity='month',
        exchange_stage_schema='stage',
        exchange_merge_partitions=true,
        unique_key=['tenant_id', 'event_id'],

        exchange_initial_partition_start_at='2024-01-01',

        distributed_by='tenant_id',
        appendoptimized=true,
        orientation='column',
        compresstype='ZSTD',
        compresslevel=1
    )
}}

select
    tenant_id,
    event_id,
    event_date,
    payload
from {{ source('raw', 'events') }}
{% if is_incremental() %}
where event_date >= date_trunc('month', current_date - interval '1 month')
{% endif %}

Important notes

• The target table must be a range-partitioned table. If a non-partitioned table with the same name already exists, the strategy raises a compile-time error. Drop it manually before the first run.
• exchange_stage_schema must exist in the database before the first run. The strategy does not create it automatically.
• Swap tables are named __swap_{model_name}_{YYYYMMDD} (day) or __swap_{model_name}_{YYYYMM} (month) and are always dropped after a successful exchange. If a run is interrupted they will be cleaned up on the next run. Model name must not exceed 47 characters (day granularity) or 49 characters (month granularity) — Greenplum enforces a 63-character limit on identifiers, and the swap table name prefix __swap_ (7 chars) plus date suffix _YYYYMMDD (9 chars) or _YYYYMM (7 chars) consumes the rest.
• The staging table is a standard dbt temporary table created by the incremental materialization before the strategy is called. It lives in the session temp schema and is dropped automatically at the end of the session. It is not created in exchange_stage_schema.
• WITHOUT VALIDATION (exchange_allow_with_validation=false) skips Greenplum's constraint check during the exchange. Use it only when you are certain the swap table data satisfies the partition constraints.
• The strategy processes only partition periods that are actually present in the staging data. Periods with no new data are never touched, so existing partition data for those periods is preserved as-is.

Table naming

Table	Schema	Example name
target (partitioned)	model schema (profiles.yml / dbt_project.yml)	marts.orders
staging	session temp schema (managed by dbt)	pg_temp.orders__dbt_tmp
swap (day)	exchange_stage_schema	stage.__swap_orders_20240101
swap (month)	exchange_stage_schema	stage.__swap_orders_202401

The staging table is a standard dbt temp table — created automatically before the strategy runs and dropped at the end of the session. Swap tables live in exchange_stage_schema and are dropped immediately after each partition exchange. The exchange_stage_schema schema must exist in the database before the first run.

Auto-creation of the partitioned table

On the first run the strategy automatically creates the target table as a PARTITION BY RANGE table — in both overwrite and merge modes:

• Column definitions are taken from the model contract (schema.yml with contract: enforced: true and data_type on each column).
• The initial partition range is defined by exchange_initial_partition_start_at and exchange_initial_partition_end_at. If exchange_initial_partition_end_at is omitted, a single partition of one period (one day or one month) is created. Further partitions are added on demand via ALTER TABLE ... ADD PARTITION.
• Partition step: EVERY (INTERVAL '1 day') or EVERY (INTERVAL '1 month') — controlled by exchange_partition_granularity.
• Distribution: DISTRIBUTED BY (<distributed_by>) or DISTRIBUTED RANDOMLY if distributed_by is not set.

On subsequent runs the check is idempotent — if the table already exists and is partitioned, creation is skipped.

If the table exists but is not partitioned, the strategy raises a compile-time error with a hint to drop it manually before re-running.

Usage examples

Schema name. By default dbt constructs the schema name as <target_schema>_<custom_schema> (e.g. public_marts). This adapter overrides that behaviour via the built-in generate_schema_name macro — the table is created exactly in the specified schema (schema='marts' → schema marts).

A model contract in schema.yml is required for all examples:

models:
  - name: orders
    config:
      contract:
        enforced: true
    columns:
      - name: id
        data_type: bigint
      - name: event_date
        data_type: date
      - name: user_id
        data_type: integer
      - name: amount
        data_type: numeric(18,4)
      - name: loaded_at
        data_type: timestamp

---

1. Append-optimised (AO) table

1.1. Overwrite mode

{{
  config(
    schema='marts',
    materialized='incremental',
    incremental_strategy='exchange_partition',
    exchange_partition_key='event_date',
    exchange_stage_schema='stage',
    exchange_merge_partitions=false,
    exchange_partition_granularity='day',
    exchange_initial_partition_start_at='2026-01-01',
    distributed_by='id',
    appendoptimized=true,
    orientation='column',
    compresstype='zstd',
    compresslevel=2
  )
}}

SELECT
    id,
    event_date::date AS event_date,
    user_id,
    amount,
    current_timestamp::timestamp AS loaded_at
FROM {{ source("ods", "orders") }}
{% if is_incremental() %}
WHERE event_date::date BETWEEN '{{ var("start_dttm") }}'::date
                             AND '{{ var("end_dttm") }}'::date
{% endif %}

The target partition is fully replaced with data from the delta.

Generated SQL (first run + one partition period):

-- Create target (first run)
CREATE TABLE marts.orders (
  "id" bigint,
  "event_date" date,
  "user_id" integer,
  "amount" numeric(18,4),
  "loaded_at" timestamp
)
WITH (
  appendoptimized=true,
  orientation=column,
  compresstype=zstd,
  compresslevel=2
)
DISTRIBUTED BY (id)
PARTITION BY RANGE (event_date) (
    START (DATE '2026-01-01') INCLUSIVE
    END   (DATE '2026-01-02') EXCLUSIVE
    EVERY (INTERVAL '1 day')
);

-- dbt creates a temp staging table automatically (heap, session temp schema):
-- CREATE TEMP TABLE orders__dbt_tmp AS ( <model SQL> ) DISTRIBUTED BY (id);

-- For each period in delta:
CREATE TABLE stage.__swap_orders_20260101
WITH (appendoptimized=true, orientation=column, compresstype=zstd, compresslevel=2)
AS
SELECT id, event_date, user_id, amount, loaded_at
FROM orders__dbt_tmp
WHERE date_trunc('day', event_date::timestamptz) = DATE '2026-01-01'
DISTRIBUTED BY (id);

ALTER TABLE marts.orders
  EXCHANGE PARTITION FOR (DATE '2026-01-01')
  WITH TABLE stage.__swap_orders_20260101;

DROP TABLE stage.__swap_orders_20260101;

-- dbt drops the temp staging table automatically at end of session

ANALYZE marts.orders;

---

1.2. Merge mode

{{
  config(
    schema='marts',
    materialized='incremental',
    incremental_strategy='exchange_partition',
    exchange_partition_key='event_date',
    exchange_stage_schema='stage',
    exchange_merge_partitions=true,
    unique_key=['id'],
    exchange_partition_granularity='day',
    distributed_by='id',
    appendoptimized=true,
    orientation='column',
    compresstype='zstd',
    compresslevel=2
  )
}}

-- Delta only — not a full source snapshot
SELECT
    id,
    event_date::date AS event_date,
    user_id,
    amount,
    current_timestamp::timestamp AS loaded_at
FROM {{ source("ods", "orders") }}
{% if is_incremental() %}
WHERE updated_at BETWEEN '{{ var("start_dttm") }}'::timestamp
                      AND '{{ var("end_dttm") }}'::timestamp
{% endif %}

When id matches, delta rows win. Target rows not present in the delta are preserved.

Generated SQL (incremental run, one partition period):

-- dbt creates a temp staging table automatically (heap, session temp schema):
-- CREATE TEMP TABLE orders__dbt_tmp AS ( <model SQL> ) DISTRIBUTED BY (id);

-- For each period in delta:
CREATE TABLE stage.__swap_orders_20260101
WITH (appendoptimized=true, orientation=column, compresstype=zstd, compresslevel=2)
AS
-- delta rows (always included, win on key conflict)
SELECT id, event_date, user_id, amount, loaded_at
FROM orders__dbt_tmp
WHERE date_trunc('day', event_date::timestamptz) = DATE '2026-01-01'

UNION ALL

-- target rows not present in delta by merge key (preserved)
SELECT id, event_date, user_id, amount, loaded_at
FROM marts.orders __trg
WHERE date_trunc('day', __trg.event_date::timestamptz) = DATE '2026-01-01'
  AND NOT EXISTS (
      SELECT 1
      FROM orders__dbt_tmp __delta
      WHERE date_trunc('day', __delta.event_date::timestamptz) = DATE '2026-01-01'
        AND __trg."id" = __delta."id"
  )
DISTRIBUTED BY (id);

ALTER TABLE marts.orders
  EXCHANGE PARTITION FOR (DATE '2026-01-01')
  WITH TABLE stage.__swap_orders_20260101;

DROP TABLE stage.__swap_orders_20260101;

-- dbt drops the temp staging table automatically at end of session

ANALYZE marts.orders;

---

2. Heap table

Distribution: if distributed_by is not set, the table is created with DISTRIBUTED RANDOMLY. DISTRIBUTED REPLICATED is not supported: partitioned tables in Greenplum 6 are incompatible with replicated distribution.

2.1. Overwrite mode

{{
  config(
    schema='marts',
    materialized='incremental',
    incremental_strategy='exchange_partition',
    exchange_partition_key='event_date',
    exchange_stage_schema='stage',
    exchange_merge_partitions=false,
    exchange_partition_granularity='day',
    exchange_initial_partition_start_at='2026-01-01',
    distributed_by='id'
  )
}}

SELECT
    id,
    event_date::date AS event_date,
    user_id,
    amount,
    current_timestamp::timestamp AS loaded_at
FROM {{ source("ods", "orders") }}
{% if is_incremental() %}
WHERE event_date::date BETWEEN '{{ var("start_dttm") }}'::date
                             AND '{{ var("end_dttm") }}'::date
{% endif %}

Generated SQL (first run + one partition period):

-- Create target (first run)
CREATE TABLE marts.orders (
  "id" bigint,
  "event_date" date,
  "user_id" integer,
  "amount" numeric(18,4),
  "loaded_at" timestamp
)
DISTRIBUTED BY (id)
PARTITION BY RANGE (event_date) (
    START (DATE '2026-01-01') INCLUSIVE
    END   (DATE '2026-01-02') EXCLUSIVE
    EVERY (INTERVAL '1 day')
);

-- dbt creates a temp staging table automatically (heap, session temp schema):
-- CREATE TEMP TABLE orders__dbt_tmp AS ( <model SQL> ) DISTRIBUTED BY (id);

CREATE TABLE stage.__swap_orders_20260101
AS
SELECT id, event_date, user_id, amount, loaded_at
FROM orders__dbt_tmp
WHERE date_trunc('day', event_date::timestamptz) = DATE '2026-01-01'
DISTRIBUTED BY (id);

ALTER TABLE marts.orders
  EXCHANGE PARTITION FOR (DATE '2026-01-01')
  WITH TABLE stage.__swap_orders_20260101;

DROP TABLE stage.__swap_orders_20260101;

-- dbt drops the temp staging table automatically at end of session

ANALYZE marts.orders;

---

2.2. Merge mode

{{
  config(
    schema='marts',
    materialized='incremental',
    incremental_strategy='exchange_partition',
    exchange_partition_key='event_date',
    exchange_stage_schema='stage',
    exchange_merge_partitions=true,
    unique_key=['id'],
    exchange_partition_granularity='day',
    distributed_by='id'
  )
}}

-- Delta only — not a full source snapshot
SELECT
    id,
    event_date::date AS event_date,
    user_id,
    amount,
    current_timestamp::timestamp AS loaded_at
FROM {{ source("ods", "orders") }}
{% if is_incremental() %}
WHERE updated_at BETWEEN '{{ var("start_dttm") }}'::timestamp
                      AND '{{ var("end_dttm") }}'::timestamp
{% endif %}

Generated SQL (incremental run, one partition period):

-- dbt creates a temp staging table automatically (heap, session temp schema):
-- CREATE TEMP TABLE orders__dbt_tmp AS ( <model SQL> ) DISTRIBUTED BY (id);

CREATE TABLE stage.__swap_orders_20260101
AS
-- delta rows (always included, win on key conflict)
SELECT id, event_date, user_id, amount, loaded_at
FROM orders__dbt_tmp
WHERE date_trunc('day', event_date::timestamptz) = DATE '2026-01-01'

UNION ALL

-- target rows not present in delta by merge key (preserved)
SELECT id, event_date, user_id, amount, loaded_at
FROM marts.orders __trg
WHERE date_trunc('day', __trg.event_date::timestamptz) = DATE '2026-01-01'
  AND NOT EXISTS (
      SELECT 1
      FROM orders__dbt_tmp __delta
      WHERE date_trunc('day', __delta.event_date::timestamptz) = DATE '2026-01-01'
        AND __trg."id" = __delta."id"
  )
DISTRIBUTED BY (id);

ALTER TABLE marts.orders
  EXCHANGE PARTITION FOR (DATE '2026-01-01')
  WITH TABLE stage.__swap_orders_20260101;

DROP TABLE stage.__swap_orders_20260101;

-- dbt drops the temp staging table automatically at end of session

ANALYZE marts.orders;

---

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