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Common features

PicklingStrategy

PicklingStrategy specifies the way how pickle serializes the sqlitecollection containers. Currently following two methods are supported:

PicklingStrategy.whole_table

The resulting pickle contains all the records in the collection. It dumps all the records into temporary sqlite3 database file when it is loaded.

PicklingStrategy.only_file_name

The resulting pickle contains only the file path of the sqlite3 database file. The file path is a relative path returned by os.path.relpath, so it must be loaded with the same structure.

MetadataItem

MetadataItem(...)

Constructor for MetadataItem. Instances of this class are not supposed to be created directly by the user.

Arguments:

  • table_name: str; table name.
  • container_type: str; container type name.
  • schema_version: str; schema version.

table_name

Read-only property for the table name.

Return value:

str: The table name.

container_type

Read-only property for the container type.

Return value:

str: The container type.

schema_version

Read-only property for the schema version

Return value:

str: The schema version.

MetadataReader

MetadataReader(...)

Constructor for MetadataReader class which can iterate over all records in the given connection.

Arguments:

  • connection: str or sqlite3.Connection; Connection to sqlite3 to get metadata. If connection is a str, it will be used as the sqlite3 database file name. You can pass a sqlite3.Connection directly.

len(metadata_reader)

Return the number of records in the metadata table read by metadata_reader. It coincides the number of collections in the sqlite3 database connected by metadata_reader._connection.

Return value:

int: The number of items in the metadata table.

obj in metadata_reader

Return whether if obj is in metadata_reader

Arguments:

  • obj: object; object to be checked the membership.

Return value:

bool: Boolean value whether if metadata_item is in the metadata table.

iter(metadata_reader)

Return an iterator over the MetadataItem's in metadata_reader It coincides the records of metadata table in the sqlite3 database connected by metadata_reader._connection.

Return value:

Iterator[MetadataItem]: an iterator over the MetadataItem's in metadata_reader