SchemaBuilder

class lsst.daf.butler.SchemaBuilder(config, limited=False)

Bases: object

Builds a Schema step-by-step.

Parameters:

config : SchemaConfig

Configuration to parse.

limited : bool

If True, ignore tables, views, and associated foreign keys whose config descriptions include a “limited” key set to False.

Attributes:

metadata : sqlalchemy.MetaData

The sqlalchemy schema description.

tables : dict

A mapping from table or view name to the associated SQLAlchemy object. Note that this contains both true tables and views.

views : set

The names of all entries in tables that are actually implemented as views.

Attributes Summary

VALID_COLUMN_TYPES

Methods Summary

addColumn(table, columnDescription)	Add a column to a table.
addForeignKeyConstraint(table, …)	Add a ForeignKeyConstraint to a table.
addTable(tableName, tableDescription)	Add a table to the schema metadata.
isIncluded(name)	Return True if the named table or view should be included in this schema.
isView(name)	Return True if the named table should be added / has been added as a view.
makeColumn(columnDescription)	Make a Column entry for addition to a Table.
normalizeForeignKeyConstraint(…)	Convert configuration for a ForeignKeyConstraint to standard form and return the target table.

Attributes Documentation

VALID_COLUMN_TYPES = {'blob': <class 'sqlalchemy.sql.sqltypes.LargeBinary'>, 'bool': <class 'sqlalchemy.sql.sqltypes.Boolean'>, 'datetime': <class 'sqlalchemy.sql.sqltypes.DateTime'>, 'float': <class 'sqlalchemy.sql.sqltypes.Float'>, 'hash': <class 'lsst.daf.butler.core.schema.Base64Bytes'>, 'int': <class 'sqlalchemy.sql.sqltypes.Integer'>, 'region': <class 'sqlalchemy.sql.sqltypes.LargeBinary'>, 'string': <class 'sqlalchemy.sql.sqltypes.String'>}

Methods Documentation

addColumn(table, columnDescription)

Add a column to a table.

Parameters:

table : sqlalchemy.Table, sqlalchemy.expression.TableClause, str

The table.

columnDescription : dict

Description of the column to be created. Should always contain:

• name, descriptive name
• type, valid column type

May contain:

• nullable, entry can be null
• primary_key, mark this column as primary key
• foreign_key, link to other table
• length, length of the field
• nbytes, length of decoded string (only for type=='hash')
• doc, docstring

addForeignKeyConstraint(table, constraintDescription)

Add a ForeignKeyConstraint to a table.

If the table or the ForeignKeyConstraint’s target are views, or should not be included in this schema (because it is limited), does nothing.

Parameters:

table : sqlalchemy.Table or str

The table.

constraintDescription : dict

Description of the ForeignKeyConstraint to be created. Should always contain: - src, list of source column names - tgt, list of target column names May also contain: - onDelete, one of “SET NULL” or “CASCADE”.

addTable(tableName, tableDescription)

Add a table to the schema metadata.

Parameters:

tableName : str

Key of the table.

tableDescription : dict

Table description.

Requires: - columns, a list of column descriptions - foreignKeys, a list of foreign-key constraint descriptions

Raises:

ValueError

If a table with the given name already exists.

isIncluded(name)

Return True if the named table or view should be included in this schema.

Parameters:

name : str

Name of a table or view. Does not need to have been added.

Returns:

included : bool

Whether the table or view should be included in the schema.

isView(name)

Return True if the named table should be added / has been added as a view.

Parameters:

name : str

Name of a table or view. Does not need to have been added.

Returns:

view : bool

Whether the table should be added / has been added as a view.

makeColumn(columnDescription)

Make a Column entry for addition to a Table.

Parameters:

columnDescription : dict

Description of the column to be created. Should always contain: - name, descriptive name - type, valid column type May contain: - nullable, entry can be null - primary_key, mark this column as primary key - length, length of the field - nbytes, length of decoded string (only for type=='hash') - doc, docstring

Returns:

c : sqlalchemy.Column

The created Column entry.

Raises:

ValueError

If the column description contains unsupported arguments

normalizeForeignKeyConstraint(constraintDescription)

Convert configuration for a ForeignKeyConstraint to standard form and return the target table.

Parameters:

constraintDescription : dict

Description of the ForeignKeyConstraint to be created. Should always contain:

• src, list of source column names or single source column name.
• tgt, list of (table-qualified) target column names or single target column name.

May also contain:

• onDelete, one of “SET NULL” or “CASCADE”.

Returns:

src : tuple

Sequence of field names in the local table.

tgt : tuple

Sequence of table-qualified field names in the remote table.

tgtTable : str

Name of the target table.

onDelete : str, optional

One of “SET NULL”, “CASCADE”, or None.