superset/datasets/models.py

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"""
Dataset model.

This model was introduced in SIP-68 (https://github.com/apache/superset/issues/14909),
and represents a "dataset" -- either a physical table or a virtual. In addition to a
dataset, new models for columns, metrics, and tables were also introduced.

These models are not fully implemented, and shouldn't be used yet.
"""

from typing import List

import sqlalchemy as sa
from flask_appbuilder import Model
from sqlalchemy.orm import backref, relationship

from superset import security_manager
from superset.columns.models import Column
from superset.models.core import Database
from superset.models.helpers import (
    AuditMixinNullable,
    ExtraJSONMixin,
    ImportExportMixin,
)
from superset.tables.models import Table

dataset_column_association_table = sa.Table(
    "sl_dataset_columns",
    Model.metadata,  # pylint: disable=no-member
    sa.Column(
        "dataset_id",
        sa.ForeignKey("sl_datasets.id"),
        primary_key=True,
    ),
    sa.Column(
        "column_id",
        sa.ForeignKey("sl_columns.id"),
        primary_key=True,
    ),
)

dataset_table_association_table = sa.Table(
    "sl_dataset_tables",
    Model.metadata,  # pylint: disable=no-member
    sa.Column("dataset_id", sa.ForeignKey("sl_datasets.id"), primary_key=True),
    sa.Column("table_id", sa.ForeignKey("sl_tables.id"), primary_key=True),
)

dataset_user_association_table = sa.Table(
    "sl_dataset_users",
    Model.metadata,  # pylint: disable=no-member
    sa.Column("dataset_id", sa.ForeignKey("sl_datasets.id"), primary_key=True),
    sa.Column("user_id", sa.ForeignKey("ab_user.id"), primary_key=True),
)


class Dataset(Model, AuditMixinNullable, ExtraJSONMixin, ImportExportMixin):
    """
    A table/view in a database.
    """

    __tablename__ = "sl_datasets"

    id = sa.Column(sa.Integer, primary_key=True)
    database_id = sa.Column(sa.Integer, sa.ForeignKey("dbs.id"), nullable=False)
    database: Database = relationship(
        "Database",
        backref=backref("datasets", cascade="all, delete-orphan"),
        foreign_keys=[database_id],
    )
    # The relationship between datasets and columns is 1:n, but we use a
    # many-to-many association table to avoid adding two mutually exclusive
    # columns(dataset_id and table_id) to Column
    columns: List[Column] = relationship(
        "Column",
        secondary=dataset_column_association_table,
        cascade="all, delete-orphan",
        single_parent=True,
        backref="datasets",
    )
    owners = relationship(
        security_manager.user_model, secondary=dataset_user_association_table
    )
    tables: List[Table] = relationship(
        "Table", secondary=dataset_table_association_table, backref="datasets"
    )

    # Does the dataset point directly to a ``Table``?
    is_physical = sa.Column(sa.Boolean, default=False)

    # Column is managed externally and should be read-only inside Superset
    is_managed_externally = sa.Column(sa.Boolean, nullable=False, default=False)

    # We use ``sa.Text`` for these attributes because (1) in modern databases the
    # performance is the same as ``VARCHAR``[1] and (2) because some table names can be
    # **really** long (eg, Google Sheets URLs).
    #
    # [1] https://www.postgresql.org/docs/9.1/datatype-character.html
    name = sa.Column(sa.Text)
    expression = sa.Column(sa.Text)
    external_url = sa.Column(sa.Text, nullable=True)

    def __repr__(self) -> str:
        return f"<Dataset id={self.id} database_id={self.database_id} {self.name}>"