Merge pull request #2099 from castrapel/count_accurate
More accurate db count functionality
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commit
d5bf85b3b0
@ -10,8 +10,8 @@
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.. moduleauthor:: Kevin Glisson <kglisson@netflix.com>
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"""
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from inflection import underscore
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from sqlalchemy import exc, func
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from sqlalchemy.orm import make_transient
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from sqlalchemy import exc, func, distinct
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from sqlalchemy.orm import make_transient, lazyload
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from sqlalchemy.sql import and_, or_
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from lemur.exceptions import AttrNotFound, DuplicateError
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@ -273,7 +273,31 @@ def get_count(q):
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:param q:
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:return:
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"""
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count_q = q.statement.with_only_columns([func.count()]).group_by(None).order_by(None)
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disable_group_by = False
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if len(q._entities) > 1:
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# currently support only one entity
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raise Exception('only one entity is supported for get_count, got: %s' % q)
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entity = q._entities[0]
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if hasattr(entity, 'column'):
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# _ColumnEntity has column attr - on case: query(Model.column)...
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col = entity.column
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if q._group_by and q._distinct:
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# which query can have both?
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raise NotImplementedError
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if q._group_by or q._distinct:
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col = distinct(col)
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if q._group_by:
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# need to disable group_by and enable distinct - we can do this because we have only 1 entity
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disable_group_by = True
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count_func = func.count(col)
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else:
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# _MapperEntity doesn't have column attr - on case: query(Model)...
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count_func = func.count()
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if q._group_by and not disable_group_by:
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count_func = count_func.over(None)
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count_q = q.options(lazyload('*')).statement.with_only_columns([count_func]).order_by(None)
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if disable_group_by:
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count_q = count_q.group_by(None)
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count = q.session.execute(count_q).scalar()
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return count
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