Query Services

The most of the time you will never initiate these services directly, you will use Container to register or get the instances of these services instead:

amsdal_glue.services.DefaultSchemaQueryService

Bases: SchemaQueryService

DefaultSchemaQueryService is responsible for executing schema query operations.

Example

Here is an example to run a schema query operation:

from amsdal_glue import init_default_containers
from amsdal_glue import Container
from amsdal_glue import Conditions, Condition, FieldReference, FieldLookup, Value, Field
from amsdal_glue import SchemaQueryOperation
from amsdal_glue.services import SchemaQueryService

# Register default containers
init_default_containers()

# Get the registered DefaultSchemaQueryService
service = Container.services.get(SchemaQueryService)

# Query `users` schema
service.execute(
    SchemaQueryOperation(
        filters=Conditions(
            Condition(
                field=FieldReference(field=Field(name='name'), table_name='amsdal_schema_registry'),
                lookup=FieldLookup.EQ,
                value=Value('users'),
            )
        ),
    ),
)

Note, the amsdal_schema_registry is reserved AMSDAL Glue name of the schema registry table. Use it to filter the schemas by name.

execute

execute(query_op)

Executes the given schema query operation.

Parameters:

Name	Type	Description	Default
query_op	SchemaQueryOperation	The schema query operation to be executed.	required

Returns:

Name	Type	Description
SchemaResult	SchemaResult	The result of the schema query operation execution.

amsdal_glue.services.DefaultDataQueryService

Bases: DataQueryService

DefaultDataQueryService is responsible for executing data query operations.

Example

Here is an example to run a data query operation:

from amsdal_glue import init_default_containers
from amsdal_glue import Container
from amsdal_glue import FieldReference, FieldLookup, Value, Field
from amsdal_glue import DataQueryOperation
from amsdal_glue.services import DataQueryService

# Register default containers
init_default_containers()

# Get the registered DefaultDataQueryService
service = Container.services.get(DataQueryService)

# Query `users` schema and get only `first_name` and `last_name` fields
service.execute(
    DataQueryOperation(
        query=QueryStatement(
            table=SchemaReference(name='users', version=Version.LATEST),
            only=[
                FieldReference(field=Field(name='first_name'), table_name='users'),
                FieldReference(field=Field(name='last_name'), table_name='users'),
            ],
        ),
    ),
)

execute

execute(query_op)

Executes the given data query operation.

Parameters:

Name	Type	Description	Default
query_op	DataQueryOperation	The data query operation to be executed.	required

Returns:

Name	Type	Description
DataResult	DataResult	The result of the data query operation execution.