def read_schema(path: util.PathLike) -> Schema:
"""
Instantiate schema dict from a schema file given by *path*.
If *path* is a directory, use the relations file under *path*. If
*path* is a file, use it directly as the schema's path. Otherwise
raise a :exc:`TSDBSchemaError`.
"""
path = Path(path).expanduser()
if path.is_dir():
path = path.joinpath(SCHEMA_FILENAME)
if not path.is_file():
raise TSDBSchemaError(f'no valid schema file at {path!s}')
return _parse_schema(path.read_text())
def write_database(db: Database,
path: util.PathLike,
names: Iterable[str] = None,
schema: SchemaLike = None,
gzip: bool = False,
encoding: str = 'utf-8') -> None:
"""
Write TSDB database *db* to *path*.
If *path* is an existing file (not a directory), a
:class:`TSDBError` is raised. If *path* is an existing directory,
the files for all relations in the destination schema will be
cleared. Every relation name in *names* must exist in the
destination schema. If *schema* is given (even if it is the same
as for *db*), every record will be remade (using
:func:`make_record`) using the schema, and columns may be dropped
or `None` values inserted as necessary, but no more sophisticated
changes will be made.
.. warning::
If *path* points to an existing directory, all relation files
defined by the schema will be overwritten or deleted.
Args:
db: Database containing data to write
path: the path to the destination database directory
names: list of names of relations to write; if `None` use all
relations in the destination schema
schema: the destination database schema; if `None` use the
schema of *db*
gzip: if `True`, compress all non-empty files; if `False`, do
not compress
encoding: character encoding for the database files
"""
path = Path(path).expanduser()
if path.is_file():
raise TSDBError(f'not a directory: {path!s}')
remake_records = schema is not None
if schema is None:
schema = db.schema
elif isinstance(schema, (str, Path)):
schema = read_schema(schema)
if names is None:
names = list(schema)
# Prepare destination directory
path.mkdir(exist_ok=True)
write_schema(path, schema)
for name in names:
fields = schema[name]
relation: Iterable[Record] = []
if name in db.schema:
try:
relation = db[name]
except (TSDBError, KeyError):
pass
if remake_records:
relation = _remake_records(relation, db.schema[name], fields)
write(path,
name,
relation,
fields,
append=False,
gzip=gzip,
encoding=encoding)
# only delete other files at the end in case db.path == path
_cleanup_files(path, set(schema).difference(names))