add key configs for adapters using microbatch

website/docs/docs/build/incremental-microbatch.md

@@ -36,7 +36,7 @@ Each "batch" corresponds to a single bounded time period (by default, a single d
 
 This is a powerful abstraction that makes it possible for dbt to run batches [separately](#backfills), concurrently, and [retry](#retry) them independently.
 
-### Example
+## Example
 
 A `sessions` model aggregates and enriches data that comes from two other models:
 - `page_views` is a large, time-series table. It contains many rows, new records almost always arrive after existing ones, and existing records rarely update. It uses the `page_view_start` column as its `event_time`.
@@ -175,22 +175,63 @@ It does not matter whether the table already contains data for that day. Given t
 
 <Lightbox src="/img/docs/building-a-dbt-project/microbatch/microbatch_filters.png" title="Each batch of sessions filters page_views to the matching time-bound batch, but doesn't filter sessions, performing a full scan for each batch."/>
 
-### Relevant configs
+## Relevant configs
 
 Several configurations are relevant to microbatch models, and some are required:
 
-| Config   | Type | Description   | Default |
-|----------|------|---------------|---------|
-| [`event_time`](/reference/resource-configs/event-time) | Column  (required)   | The column indicating "at what time did the row occur." Required for your microbatch model and any direct parents that should be filtered.          | N/A     |
-| `begin`      | Date (required)   | The "beginning of time" for the microbatch model. This is the starting point for any initial or full-refresh builds. For example, a daily-grain microbatch model run on `2024-10-01` with `begin = '2023-10-01` will process 366 batches (it's a leap year!) plus the batch for "today."        | N/A     |
-| `batch_size` | String (required)  | The granularity of your batches. Supported values are `hour`, `day`, `month`, and `year`             | N/A     |
-| `lookback`   | Integer (optional) | Process X batches prior to the latest bookmark to capture late-arriving records.                                         | `1`     |
+| Config   |  Description   | Default | Type | Required  |
+|----------|---------------|---------|------|---------|
+| [`event_time`](/reference/resource-configs/event-time)  | The column indicating "at what time did the row occur." Required for your microbatch model and any direct parents that should be filtered.   | N/A     |  Column  |  Required |
+| `begin`      |  The "beginning of time" for the microbatch model. This is the starting point for any initial or full-refresh builds. For example, a daily-grain microbatch model run on `2024-10-01` with `begin = '2023-10-01` will process 366 batches (it's a leap year!) plus the batch for "today."        | N/A     | Date   | Required |
+| `batch_size` |  The granularity of your batches. Supported values are `hour`, `day`, `month`, and `year`    | N/A     | String  | Required |
+| `lookback`   | Process X batches prior to the latest bookmark to capture late-arriving records.    | `1`     | Integer | Optional |
 
 <Lightbox src="/img/docs/building-a-dbt-project/microbatch/event_time.png" title="The event_time column configures the real-world time of this record"/>
 
+### Required configs for specific adapters
+Some adapters require additional configurations for the microbatch strategy. This is because each adapter implements the microbatch strategy differently.
+
+The following table lists the required configurations for the specific adapters, in addition to the standard microbatch configs:
+
+| Adapter  | `unique_key` config | `partition_by` config |
+|----------|------------------|--------------------|
+| [`dbt-postgres`](/reference/resource-configs/postgres-configs#incremental-materialization-strategies) | ✅ Required | N/A |
+| [`dbt-spark`](/reference/resource-configs/spark-configs#incremental-models)    | N/A | ✅ Required |
+| [`dbt-bigquery`](/reference/resource-configs/bigquery-configs#merge-behavior-incremental-models) | N/A | ✅ Required |
+
+For example, if you're using `dbt-postgres`, configure `unique_key` as follows:
+
+<File name="models/sessions.sql">
+
+```sql
+{{ config(
+    materialized='incremental',
+    incremental_strategy='microbatch',
+    unique_key='sales_id', ## required for dbt-postgres
+    event_time='transaction_date',
+    begin='2023-01-01',
+    batch_size='day'
+) }}
+
+select
+    sales_id,
+    transaction_date,
+    customer_id,
+    product_id,
+    total_amount
+from {{ source('sales', 'transactions') }}
+
+```
+
+ In this example, `unique_key` is required because `dbt-postgres` microbatch uses the `merge` strategy, which needs a `unique_key` to identify which rows in the data warehouse need to get merged. Without a `unique_key`, dbt won't be able to match rows between the incoming batch and the existing table.
+
+</File>
+
+### Full refresh
+
 As a best practice, we recommend configuring `full_refresh: False` on microbatch models so that they ignore invocations with the `--full-refresh` flag. If you need to reprocess historical data, do so with a targeted backfill that specifies explicit start and end dates.
 
-### Usage
+## Usage
 
 **You must write your model query to process (read and return) exactly one "batch" of data**. This is a simplifying assumption and a powerful one:
 - You don’t need to think about `is_incremental` filtering
@@ -207,7 +248,7 @@ During standard incremental runs, dbt will process batches according to the curr
 
 **Note:** If there’s an upstream model that configures `event_time`, but you *don’t* want the reference to it to be filtered, you can specify `ref('upstream_model').render()` to opt-out of auto-filtering. This isn't generally recommended — most models that configure `event_time` are fairly large, and if the reference is not filtered, each batch will perform a full scan of this input table.
 
-### Backfills
+## Backfills
 
 Whether to fix erroneous source data or retroactively apply a change in business logic, you may need to reprocess a large amount of historical data.
 
@@ -222,13 +263,13 @@ dbt run --event-time-start "2024-09-01" --event-time-end "2024-09-04"
 
 <Lightbox src="/img/docs/building-a-dbt-project/microbatch/microbatch_backfill.png" title="Configure a lookback to reprocess additional batches during standard incremental runs"/>
 
-### Retry
+## Retry
 
 If one or more of your batches fail, you can use `dbt retry` to reprocess _only_ the failed batches.
 
 ![Partial retry](https://github.com/user-attachments/assets/f94c4797-dcc7-4875-9623-639f70c97b8f)
 
-### Timezones
+## Timezones
 
 For now, dbt assumes that all values supplied are in UTC: