ButlerAttributeManager

class lsst.daf.butler.registry.interfaces.ButlerAttributeManager

Bases: abc.ABC

An interface for managing butler attributes in a Registry.

Attributes are represented in registry as a set of name-value pairs, both have string type. Any non-string data types (e.g. integers) need to be converted to/from strings on client side. Attribute names can be arbitrary strings, no particular structure is enforced by this interface. Attribute names are globally unique, to avoid potential collision clients should follow some common convention for attribute names, e.g. dot-separated components (config.managers.opaque).

One of the critical pieces of information that will be stored as attribute is the version of database schema which needs to be known before registry can do any operations on database. For that reasons it is likely there will be only one implementation of this interface which uses database table with a stable schema.

Methods Summary

delete(name)	Delete an attribute.
get(name, default)	Retrieve value of a given attribute.
initialize(db, context)	Construct an instance of the manager.
items()	Iterate over attributes and yield their names and values.
set(name, value, *, force)	Set value for a given attribute.

Methods Documentation

delete(name: str) → bool

Delete an attribute.

Parameters:

name : str

Attribute name, arbitrary non-empty string.

Returns:

existed : bool

True is returned if attribute existed before it was deleted.

get(name: str, default: Optional[str] = None) → Optional[str]

Retrieve value of a given attribute.

Parameters:

name : str

Attribute name, arbitrary non-empty string.

default : str, optional

Default value returned when attribute does not exist, can be string or None.

Returns:

value : str

Attribute value, if attribute does not exist then default is returned.

classmethod initialize(db: Database, context: StaticTablesContext) → ButlerAttributeManager

Construct an instance of the manager.

Parameters:

db : Database

Interface to the underlying database engine and namespace.

context : StaticTablesContext

Context object obtained from Database.declareStaticTables; used to declare any tables that should always be present in a layer implemented with this manager.

Returns:

manager : ButlerAttributeManager

An instance of ButlerAttributeManager.

items() → Iterable[Tuple[str, str]]

Iterate over attributes and yield their names and values.

Yields:

name : str

Attribute name.

value : str

Corresponding attribute value.

set(name: str, value: str, *, force: bool = False) → None

Set value for a given attribute.

Parameters:

name : str

Attribute name, arbitrary non-empty string.

value : str

New value for an attribute, an arbitrary string. Due to deficiencies of some database engines we are not allowing empty strings to be stored in the database, and value cannot be an empty string.

force : bool, optional

Controls handling of existing attributes. With default False value an exception is raised if attribute name already exists, if True is passed then value of the existing attribute will be updated.

Raises:

ButlerAttributeExistsError

Raised if attribute already exists but force option is false.

ValueError

Raised if name or value parameters are empty.