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""" |
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byceps.database |
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~~~~~~~~~~~~~~~ |
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Database utilities. |
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:Copyright: 2006-2019 Jochen Kupperschmidt |
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:License: Modified BSD, see LICENSE for details. |
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""" |
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from typing import Any, Callable, Dict, Iterable, TypeVar |
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import uuid |
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from sqlalchemy.dialects.postgresql import insert |
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from sqlalchemy.sql.dml import Insert |
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from sqlalchemy.sql.schema import Table |
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from flask_sqlalchemy import BaseQuery, Pagination, SQLAlchemy |
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from sqlalchemy.dialects.postgresql import JSONB, UUID |
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from sqlalchemy.orm import Query |
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F = TypeVar('F') |
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T = TypeVar('T') |
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Mapper = Callable[[F], T] |
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db = SQLAlchemy(session_options={'autoflush': False}) |
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db.JSONB = JSONB |
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class Uuid(UUID): |
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def __init__(self): |
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super().__init__(as_uuid=True) |
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db.Uuid = Uuid |
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def generate_uuid() -> uuid.UUID: |
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"""Generate a random UUID (Universally Unique IDentifier).""" |
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return uuid.uuid4() |
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def paginate(query: Query, page: int, per_page: int, |
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*, item_mapper: Mapper=None) -> Pagination: |
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"""Return `per_page` items from page `page`.""" |
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if page < 1: |
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page = 1 |
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if per_page < 1: |
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raise ValueError('The number of items per page must be positive.') |
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offset = (page - 1) * per_page |
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items = query \ |
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.limit(per_page) \ |
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.offset(offset) \ |
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.all() |
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item_count = len(items) |
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if page == 1 and item_count < per_page: |
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total = item_count |
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else: |
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total = query.order_by(None).count() |
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if item_mapper is not None: |
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items = [item_mapper(item) for item in items] |
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# Intentionally pass no query object. |
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return Pagination(None, page, per_page, total, items) |
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def insert_ignore_on_conflict(table: Table, values: Dict[str, Any]) -> None: |
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"""Insert the record identified by the primary key (specified as |
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part of the values), or do nothing on conflict. |
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""" |
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query = insert(table) \ |
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.values(**values) \ |
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.on_conflict_do_nothing(constraint=table.primary_key) |
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db.session.execute(query) |
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db.session.commit() |
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def upsert(table: Table, identifier: Dict[str, Any], |
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replacement: Dict[str, Any]) -> None: |
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"""Insert or update the record identified by `identifier` with value |
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`replacement`. |
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""" |
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query = _build_upsert_query(table, identifier, replacement) |
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db.session.execute(query) |
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db.session.commit() |
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def upsert_many(table: Table, identifiers: Iterable[Dict[str, Any]], |
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replacement: Dict[str, Any]) -> None: |
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"""Insert or update the record identified by `identifier` with value |
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`replacement`. |
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""" |
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for identifier in identifiers: |
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query = _build_upsert_query(table, identifier, replacement) |
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db.session.execute(query) |
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db.session.commit() |
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def _build_upsert_query(table: Table, identifier: Dict[str, Any], |
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replacement: Dict[str, Any]) -> Insert: |
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values = identifier.copy() |
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values.update(replacement) |
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return insert(table) \ |
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.values(**values) \ |
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.on_conflict_do_update( |
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constraint=table.primary_key, |
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set_=replacement) |
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byceps /
byceps
