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Relational

matchlab.sources.relational

Reading a source from a relational database.

Classes:

  • ClientType –

    The client libraries a relational location can be driven by.

  • RelationalDB –

    A relational database, and the query that extracts a source's rows from it.

Attributes:

  • DBClient (TypeAlias) –

    What a RelationalDB reads through: a SQLAlchemy engine or an ADBC connection.

DBClient module-attribute 

DBClient: TypeAlias = Engine | Connection

What a RelationalDB reads through: a SQLAlchemy engine or an ADBC connection.

ClientType

Bases: StrEnum


              flowchart TD
              matchlab.sources.relational.ClientType[ClientType]

              

              click matchlab.sources.relational.ClientType href "" "matchlab.sources.relational.ClientType"

The client libraries a relational location can be driven by.

Attributes:

SQLALCHEMY class-attribute instance-attribute 

SQLALCHEMY = 'sqlalchemy'

ADBC class-attribute instance-attribute 

ADBC = 'adbc'

RelationalDB

Bases: Location


              flowchart TD
              matchlab.sources.relational.RelationalDB[RelationalDB]
              matchlab.sources.base.Location[Location]

                              matchlab.sources.base.Location --> matchlab.sources.relational.RelationalDB
                


              click matchlab.sources.relational.RelationalDB href "" "matchlab.sources.relational.RelationalDB"
              click matchlab.sources.base.Location href "" "matchlab.sources.base.Location"

A relational database, and the query that extracts a source's rows from it.

Methods:

  • read –

    Get this location's rows, in batches.

Attributes:

sql instance-attribute 

sql: SQLQuery

SQL producing the rows to read, in whatever dialect the client speaks.

client instance-attribute 

client: FromResources[DBClient]

The SQLAlchemy engine or ADBC connection to read through.

client_type property 

client_type: ClientType

Which client type this location was built with.

One isinstance decides it, because the field's type has already rejected anything that is neither an Engine nor an ADBC connection.

model_config class-attribute instance-attribute 

model_config = ConfigDict(extra='forbid', frozen=True, arbitrary_types_allowed=True)

read 

read(batch_size: int | None = None, rename: dict[str, str] | Callable | None = None, return_type: DataFrameType = POLARS, schema_overrides: dict[str, DataType] | None = None) -> Generator[DataFrameClass, None, None]

Get this location's rows, in batches.

Parameters:

  • batch_size
    (int | None, default: None ) –

    The size used for internal batching.

  • rename
    (dict[str, str] | Callable | None, default: None ) –

    Renaming to apply to the rows that come back.

    • If a dictionary is provided, it will be used to rename the columns.
    • If a callable is provided, it will take the old name as input and return the new name.
  • return_type
    (DataFrameType, default: POLARS ) –

    The type of data to return. Defaults to "polars".

  • schema_overrides
    (dict[str, DataType] | None, default: None ) –

    Types to force on the columns that come back, rather than letting the location infer them.