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Version: 1.4.1 (latest)

Create and use own naming convention

info

The source code for this example can be found in our repository at: https://github.com/dlt-hub/dlt/tree/devel/docs/examples/custom_naming

About this Example

This example shows how to add and use custom naming convention. Naming conventions translate identifiers found in source data into identifiers in destination, where rules for a valid identifier are constrained.

Custom naming conventions are classes that derive from NamingConvention that you can import from dlt.common.normalizers.naming. We recommend the following module layout:

  1. Each naming convention resides in a separate Python module (file)
  2. The class is always named NamingConvention

There are two naming conventions in this example:

  1. A variant of sql_ci that generates identifier collisions with a low (user defined) probability by appending a deterministic tag to each name.
  2. A variant of sql_cs that allows for LATIN (ie. umlaut) characters

With this example you will learn to:

  • Create a naming convention module with a recommended layout
  • Use naming convention by explicitly passing it to duckdb destination factory
  • Use naming convention by configuring it config.toml
  • Changing the declared case sensitivity by overriding is_case_sensitive property
  • Providing custom normalization logic by overriding normalize_identifier method

Full source code

import dlt

if __name__ == "__main__":
# sql_cs_latin2 module
import sql_cs_latin2 # type: ignore[import-not-found]

# create postgres destination with a custom naming convention. pass sql_cs_latin2 as module
# NOTE: ql_cs_latin2 is case sensitive and postgres accepts UNICODE letters in identifiers
dest_ = dlt.destinations.postgres(
"postgresql://loader:loader@localhost:5432/dlt_data", naming_convention=sql_cs_latin2
)
# run a pipeline
pipeline = dlt.pipeline(
pipeline_name="sql_cs_latin2_pipeline",
destination=dest_,
dataset_name="example_data",
dev_mode=True,
)
# Extract, normalize, and load the data
load_info = pipeline.run([{"StückId": 1}], table_name="Ausrüstung")
print(load_info)
with pipeline.sql_client() as client:
# NOTE: we quote case sensitive identifers
with client.execute_query('SELECT "StückId" FROM "Ausrüstung"') as cur:
print(cur.description)
print(cur.fetchone())

# sql_ci_no_collision (configured in config toml)
# NOTE: pipeline with name `sql_ci_no_collision` will create default schema with the same name
# so we are free to use it in config.toml to just affect this pipeline and leave the postgres pipeline as it is
pipeline = dlt.pipeline(
pipeline_name="sql_ci_no_collision",
destination="duckdb",
dataset_name="example_data",
dev_mode=True,
)
# duckdb is case insensitive so tables and columns below would clash but sql_ci_no_collision prevents that
data_1 = {"ItemID": 1, "itemid": "collides"}
load_info = pipeline.run([data_1], table_name="BigData")

data_2 = {"1Data": 1, "_1data": "collides"}
# use colliding table
load_info = pipeline.run([data_2], table_name="bigdata")

with pipeline.sql_client() as client:
from duckdb import DuckDBPyConnection

conn: DuckDBPyConnection = client.native_connection
# tags are deterministic so we can just use the naming convention to get table names to select
first_table = pipeline.default_schema.naming.normalize_table_identifier("BigData")
sql = f"DESCRIBE TABLE {first_table}"
print(sql)
print(conn.sql(sql))
second_table = pipeline.default_schema.naming.normalize_table_identifier("bigdata")
sql = f"DESCRIBE TABLE {second_table}"
print(sql)
print(conn.sql(sql))

# print(pipeline.default_schema.to_pretty_yaml())

This demo works on codespaces. Codespaces is a development environment available for free to anyone with a Github account. You'll be asked to fork the demo repository and from there the README guides you with further steps.
The demo uses the Continue VSCode extension.

Off to codespaces!

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