我在SQLAlchemy中有一个模型，它使用关联表定义了多对多关系(这里使用automap是因为我使用的是现有数据库(：
from sqlalchemy import (Column, Table, MetaData, Integer, Text, LargeBinary,
ForeignKey, Float, Boolean, Index)
from sqlalchemy.ext.automap import automap_base, AutomapBase
from sqlalchemy.orm import Session, deferred, relationship
Base: AutomapBase = automap_base()
class VariantAssociation(Base):
__tablename__ = "sample_variant_association"
vid = Column(Integer, ForeignKey("variants.variant_id"),
primary_key=True)
sid = Column(Integer, ForeignKey("samples.sample_id"),
primary_key=True)
vdepth = Column(Integer)
valt_depth = Column(Integer)
gt = Column(Text)
gt_type = Column(Integer)
fraction = Column(Float)
variant = relationship("Variant", back_populates="samples")
sample = relationship("Sample", back_populates="variants")
__table_args__ = (Index('ix_sample_variant_association_valt_depth',
"valt_depth"),
Index('ix_sample_variant_association_vdepth',
"vdepth"),
Index('ix_sample_variant_association_vid', 'vid'),
Index('ix_sample_variant_association_sid', 'sid'),
Index('ix_sample_variant_association_fraction',
'fraction')
)
class Variant(Base):
__tablename__ = "variants"
variant_id = Column(Integer, primary_key=True)
info = deferred(Column(LargeBinary))
samples = relationship("VariantAssociation",
back_populates="variant")
class Sample(Base):
__tablename__ = "samples"
sample_id = Column(Integer, primary_key=True, index=True)
name = Column(Text, index=True)
variants = relationship("VariantAssociation",
back_populates="sample")
class SampleGenotypeCount(Base):
__tablename__ = 'sample_genotype_counts'
sample_id = Column(Integer, primary_key=True)
num_hom_ref = Column(Integer)
num_het = Column(Integer)
num_hom_alt = Column(Integer)
num_unknown = Column(Integer)
class DataMigration(Base):
__tablename__ = "datamigration"
done = Column(Boolean, primary_key=True)
在查询时，这最终会生成以下警告：
查询：
query = session.query(Variant).join(
Variant.samples).join(Sample)
警告：
/usr/local/lib/python3.9/site-packages/sqlalchemy/orm/relationships.py:3441: SAWarning:
relationship 'Variant.variantassociation_collection' will copy column variants.variant_id to
column sample_variant_association.vid, which conflicts with relationship(s): 'Variant.samples'
(copies variants.variant_id to sample_variant_association.vid). If this is not the intention,
consider if these relationships should be linked with back_populates, or if viewonly=True
should be applied to one or more if they are read-only. For the less common case that foreign
key constraints are partially overlapping, the orm.foreign() annotation can be used to isolate
the columns that should be written towards. The 'overlaps' parameter may be used to remove
this warning. (Background on this error at: http://sqlalche.me/e/14/qzyx)
我一直在查看SO和SQLAlchemy文档，但我无法找到导致此问题的原因，因为(在我看来(back_populates参数位于正确的位置。
模型中的错误在哪里？SQLAlchemy 1.3.23没有生成一个FTR。
为了设置自己的关系名称，您需要防止Automap通过iteself生成关系。您可以通过将generate_relationship设置为返回None的函数来实现这一点。
def generate_relationships(base, direction, return_fn, attrname, local_cls, referred_cls, **kw):
return None
Base.prepare(generate_relationship=generate_relationships)