77 lines
2.7 KiB
Python
77 lines
2.7 KiB
Python
import dateutil.parser
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from datetime import datetime
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from peewee import SQL
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def paginate(query, model, descending=False, page_token=None, limit=50, sort_field_alias=None,
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max_page=None, sort_field_name=None):
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""" Paginates the given query using an field range, starting at the optional page_token.
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Returns a *list* of matching results along with an unencrypted page_token for the
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next page, if any. If descending is set to True, orders by the field descending rather
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than ascending.
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"""
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# Note: We use the sort_field_alias for the order_by, but not the where below. The alias is
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# necessary for certain queries that use unions in MySQL, as it gets confused on which field
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# to order by. The where clause, on the other hand, cannot use the alias because Postgres does
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# not allow aliases in where clauses.
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sort_field_name = sort_field_name or 'id'
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sort_field = getattr(model, sort_field_name)
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if sort_field_alias is not None:
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sort_field_name = sort_field_alias
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sort_field = SQL(sort_field_alias)
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if descending:
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query = query.order_by(sort_field.desc())
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else:
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query = query.order_by(sort_field)
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start_index = pagination_start(page_token)
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if start_index is not None:
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if descending:
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query = query.where(sort_field <= start_index)
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else:
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query = query.where(sort_field >= start_index)
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query = query.limit(limit + 1)
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page_number = (page_token.get('page_number') or None) if page_token else None
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if page_number is not None and max_page is not None and page_number > max_page:
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return [], None
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return paginate_query(query, limit=limit, sort_field_name=sort_field_name,
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page_number=page_number)
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def pagination_start(page_token=None):
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""" Returns the start index for pagination for the given page token. Will return None if None. """
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if page_token is not None:
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start_index = page_token.get('start_index')
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if page_token.get('is_datetime'):
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start_index = dateutil.parser.parse(start_index)
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return start_index
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return None
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def paginate_query(query, limit=50, sort_field_name=None, page_number=None):
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""" Executes the given query and returns a page's worth of results, as well as the page token
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for the next page (if any).
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"""
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results = list(query)
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page_token = None
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if len(results) > limit:
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start_index = getattr(results[limit], sort_field_name or 'id')
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is_datetime = False
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if isinstance(start_index, datetime):
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start_index = start_index.isoformat() + "Z"
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is_datetime = True
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page_token = {
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'start_index': start_index,
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'page_number': page_number + 1 if page_number else 1,
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'is_datetime': is_datetime,
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}
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return results[0:limit], page_token
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