Replications

Replications are YAML configurations that define data movement from source to target systems.

Basic Structure

yaml

source: SOURCE_CONNECTION
target: TARGET_CONNECTION

defaults:
  mode: full-refresh
  object: '{target_schema}.{stream_table}'

streams:
  schema.table1:
  schema.table2:
    mode: incremental
    primary_key: [id]

env:
  SLING_THREADS: 5

MCP Operations

Parse (validate)

json

{"action": "parse", "input": {"file_path": "/path/to/replication.yaml"}}

Run

json

{
  "action": "run",
  "input": {
    "file_path": "/path/to/replication.yaml",
    "select_streams": ["table1"],
    "mode": "incremental"
  }
}

Modes

Mode	Description	Use Case
`full-refresh`	Drop and recreate table	Complete replacement
`incremental`	Upsert by primary key	Ongoing updates
`truncate`	Clear then load	Preserve DDL
`snapshot`	Append with timestamp	Historical tracking
`backfill`	Load date/ID ranges	Historical recovery

Incremental Strategies

Primary Key	Update Key	Strategy
Yes	Yes	Load only new records, upsert
Yes	No	Load all, upsert by PK
No	Yes	Append only new records

yaml

streams:
  orders:
    mode: incremental
    primary_key: [order_id]
    update_key: updated_at

Backfill Mode

yaml

streams:
  large_table:
    mode: backfill
    update_key: created_date
    source_options:
      range: '2023-01-01,2023-12-31'
      chunk_size: 7d

Stream Configuration

yaml

streams:
  my_table:
    object: schema.target_table     # Target table
    mode: incremental               # Loading mode
    primary_key: [id]               # PK columns
    update_key: updated_at          # Incremental key
    columns: {id: bigint, amount: decimal(10,2)}
    select: [id, name, email]       # or [-password] to exclude
    sql: |                          # Custom SQL
      SELECT * FROM my_table
      WHERE status = 'active'
    disabled: false

Wildcards and Patterns

yaml

streams:
  public.*:                    # All tables in schema
  sales.customer_*:            # Tables with prefix
  public.sensitive_data:
    disabled: true             # Exclude specific
  'data/*.csv':                # All CSV files
  'logs/**/*.json':            # Recursive matching

Variables

Variable	Description
`{stream_name}`	Full stream name
`{stream_schema}`	Source schema
`{stream_table}`	Source table
`{target_schema}`	Target default schema
`{stream_file_name}`	File name without extension
`{YYYY}`, `{MM}`, `{DD}`	Date parts

yaml

defaults:
  object: '{target_schema}.{stream_schema}_{stream_table}'

Source Options

Database Sources

Option	Description
`limit`	Max rows to read
`empty_as_null`	Treat empty strings as NULL
`chunk_size`	Time interval per chunk (e.g., `6h`)

File Sources

Option	Description
`format`	csv, json, parquet, xlsx
`header`	First row is header
`delimiter`	Column delimiter
`encoding`	Character encoding
`jmespath`	Extract JSON data

yaml

defaults:
  source_options:
    format: csv
    header: true
    encoding: utf8

Target Options

Database Targets

Option	Description
`column_casing`	snake, upper, lower, source
`add_new_columns`	Auto-add new columns
`use_bulk`	Use bulk loading

File Targets

Option	Description
`format`	csv, parquet, jsonlines
`compression`	gzip, snappy, zstd
`file_max_rows`	Split files by row count

Environment Variables

yaml

env:
  SLING_THREADS: 10           # Parallel streams
  SLING_RETRIES: 3            # Retry failed streams
  SLING_LOADED_AT_COLUMN: true

Examples

Database to Database

yaml

source: POSTGRES
target: SNOWFLAKE

defaults:
  mode: incremental
  object: 'warehouse.{stream_schema}_{stream_table}'
  primary_key: [id]
  update_key: updated_at

streams:
  public.customers:
  public.orders:
  public.products:

Files to Database

yaml

source: S3
target: POSTGRES

defaults:
  mode: full-refresh
  object: 'staging.{stream_file_name}'
  source_options:
    format: csv
    header: true

streams:
  'data/customers/*.csv':
  'data/orders/*.csv':

Database to Files

yaml

source: POSTGRES
target: S3

defaults:
  mode: full-refresh
  object: 'exports/{stream_table}/{YYYY}/{MM}/'
  target_options:
    format: parquet
    compression: snappy

streams:
  public.transactions:
  public.events:

Full Documentation

See https://docs.slingdata.io/concepts/replication.md for complete reference.