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Alembic support | ||
--------------- | ||
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`Alembic <https://alembic.sqlalchemy.org>`_ is a lightweight database | ||
migration tool for usage with the SQLAlchemy Database Toolkit for | ||
Python. It can use this BigQuery SQLAlchemy support to manage | ||
BigQuery shemas. | ||
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Some features, like management of constrains and indexes, aren't | ||
supported because `BigQuery doesn't support them | ||
<https://cloud.google.com/bigquery/docs/reference/standard-sql/data-definition-language>`_. | ||
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Supported operations: | ||
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`add_column(table_name, column, schema=None) | ||
<https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations.add_column>`_ | ||
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`alter_column(table_name, column_name, nullable=None, schema=None) | ||
<https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations.alter_column>`_ | ||
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`bulk_insert(table, rows, multiinsert=True) | ||
<https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations.bulk_insert>`_ | ||
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`create_table(table_name, *columns, **kw) | ||
<https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations.create_table>`_ | ||
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`create_table_comment(table_name, comment, schema=None) | ||
<https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations.create_table_comment>`_ | ||
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`drop_column(table_name, column_name, schema=None) | ||
<https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations.drop_column>`_ | ||
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`drop_table(table_name, schema=None) | ||
<https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations.drop_table>`_ | ||
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`drop_table_comment(table_name, schema=None) | ||
<https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations.drop_table_comment>`_ | ||
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`execute(sqltext, execution_options=None) | ||
<https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations.execute>`_ | ||
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`rename_table(old_table_name, new_table_name, schema=None) | ||
<https://alembic.sqlalchemy.org/en/latest/ops.html#alembic.operations.Operations.rename_table>`_ | ||
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Note that some of the operations above have limited capability, again | ||
do to `BigQuery limitations | ||
<https://cloud.google.com/bigquery/docs/reference/standard-sql/data-definition-language>`_. | ||
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The `execute` operation allows access to BigQuery-specific | ||
`data-definition-language | ||
<https://cloud.google.com/bigquery/docs/reference/standard-sql/data-definition-language>`_. |
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.. include:: multiprocessing.rst | ||
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.. include:: alembic.rst | ||
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API Reference | ||
------------- | ||
.. toctree:: | ||
|
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# Copyright (c) 2021 The PyBigQuery Authors | ||
# | ||
# Permission is hereby granted, free of charge, to any person obtaining a copy of | ||
# this software and associated documentation files (the "Software"), to deal in | ||
# the Software without restriction, including without limitation the rights to | ||
# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of | ||
# the Software, and to permit persons to whom the Software is furnished to do so, | ||
# subject to the following conditions: | ||
# | ||
# The above copyright notice and this permission notice shall be included in all | ||
# copies or substantial portions of the Software. | ||
# | ||
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS | ||
# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR | ||
# COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER | ||
# IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN | ||
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. | ||
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import contextlib | ||
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import pytest | ||
from sqlalchemy import Column, DateTime, Integer, String | ||
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try: | ||
import alembic # noqa | ||
except ImportError: | ||
alembic = None | ||
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import google.api_core.exceptions | ||
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@pytest.fixture | ||
def alembic_table(bigquery_dataset, bigquery_client): | ||
import sqlalchemy | ||
import alembic.migration | ||
import alembic.operations | ||
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def get_table(table_name, data="table"): | ||
try: | ||
table_id = f"{bigquery_dataset}.{table_name}" | ||
if data == "rows": | ||
return [dict(r) for r in bigquery_client.list_rows(table_id)] | ||
else: | ||
table = bigquery_client.get_table(table_id) | ||
if data == "table": | ||
return table | ||
elif data == "schema": | ||
return [ | ||
repr(s).replace(", (), None)", ")").replace(", None)", ")") | ||
for s in table.schema | ||
] | ||
else: | ||
raise ValueError(data) | ||
except google.api_core.exceptions.NotFound: | ||
return None | ||
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engine = sqlalchemy.create_engine(f"bigquery:///{bigquery_dataset}") | ||
with contextlib.closing(engine.connect()) as conn: | ||
migration_context = alembic.migration.MigrationContext.configure(conn, {}) | ||
with alembic.operations.Operations.context(migration_context): | ||
yield get_table | ||
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@pytest.mark.skipif(alembic is None, reason="Alembic isn't installed.") | ||
def test_alembic_scenario(alembic_table): | ||
""" | ||
Exercise all of the operations we support. | ||
It's a little awkward because we have to avoid doing too many | ||
operations on the same table to avoid tripping over limits on | ||
table mods within a short time. | ||
""" | ||
from alembic import op | ||
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assert alembic_table("account") is None | ||
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account = op.create_table( | ||
"account", | ||
Column("id", Integer, nullable=False), | ||
Column("name", String(50), nullable=False, comment="The name"), | ||
Column("description", String(200)), | ||
) | ||
assert alembic_table("account", "schema") == [ | ||
"SchemaField('id', 'INTEGER', 'REQUIRED')", | ||
"SchemaField('name', 'STRING(50)', 'REQUIRED', 'The name')", | ||
"SchemaField('description', 'STRING(200)', 'NULLABLE')", | ||
] | ||
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op.bulk_insert( | ||
account, | ||
[ | ||
dict(id=1, name="home", description="the home account"), | ||
dict(id=2, name="operations", description="the ops account"), | ||
dict(id=3, name="savings", description=None), | ||
], | ||
) | ||
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assert alembic_table("account", "rows") == [ | ||
{"description": "the home account", "id": 1, "name": "home"}, | ||
{"description": "the ops account", "id": 2, "name": "operations"}, | ||
{"description": None, "id": 3, "name": "savings"}, | ||
] | ||
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op.add_column( | ||
"account", Column("last_transaction_date", DateTime, comment="when updated") | ||
) | ||
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assert alembic_table("account", "schema") == [ | ||
"SchemaField('id', 'INTEGER', 'REQUIRED')", | ||
"SchemaField('name', 'STRING(50)', 'REQUIRED', 'The name')", | ||
"SchemaField('description', 'STRING(200)', 'NULLABLE')", | ||
"SchemaField('last_transaction_date', 'DATETIME', 'NULLABLE', 'when updated')", | ||
] | ||
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op.create_table( | ||
"account_w_comment", | ||
Column("id", Integer, nullable=False), | ||
Column("name", String(50), nullable=False, comment="The name"), | ||
Column("description", String(200)), | ||
comment="This table has comments", | ||
) | ||
assert alembic_table("account_w_comment").description == "This table has comments" | ||
op.drop_table_comment("account_w_comment") | ||
assert alembic_table("account_w_comment").description is None | ||
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op.drop_column("account_w_comment", "description") | ||
assert alembic_table("account_w_comment", "schema") == [ | ||
"SchemaField('id', 'INTEGER', 'REQUIRED')", | ||
"SchemaField('name', 'STRING(50)', 'REQUIRED', 'The name')", | ||
] | ||
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op.drop_table("account_w_comment") | ||
assert alembic_table("account_w_comment") is None | ||
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op.rename_table("account", "accounts") | ||
assert alembic_table("account") is None | ||
assert alembic_table("accounts", "schema") == [ | ||
"SchemaField('id', 'INTEGER', 'REQUIRED')", | ||
"SchemaField('name', 'STRING(50)', 'REQUIRED', 'The name')", | ||
"SchemaField('description', 'STRING(200)', 'NULLABLE')", | ||
"SchemaField('last_transaction_date', 'DATETIME', 'NULLABLE', 'when updated')", | ||
] | ||
op.drop_table("accounts") | ||
assert alembic_table("accounts") is None | ||
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op.execute( | ||
""" | ||
create table transactions( | ||
account INT64 NOT NULL, | ||
transaction_time DATETIME NOT NULL, | ||
amount NUMERIC(11, 2) NOT NULL | ||
) | ||
partition by DATE(transaction_time) | ||
""" | ||
) | ||
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# The only thing we can alter about a column is we can make it | ||
# nullable: | ||
op.alter_column("transactions", "amount", True) | ||
assert alembic_table("transactions", "schema") == [ | ||
"SchemaField('account', 'INTEGER', 'REQUIRED')", | ||
"SchemaField('transaction_time', 'DATETIME', 'REQUIRED')", | ||
"SchemaField('amount', 'NUMERIC(11, 2)', 'NULLABLE')", | ||
] | ||
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op.create_table_comment("transactions", "Transaction log") | ||
assert alembic_table("transactions").description == "Transaction log" | ||
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op.drop_table("transactions") |