SQLAlchemy-将where子句添加到select会生成子查询

Question

Select.where的文档说该方法应该在现有的SELECT查询后附加WHERE子句，但有时似乎将select包装为子查询，从而导致ProgrammingError: (psycopg2.ProgrammingError) subquery in FROM must have an alias错误。 这似乎仅在我尝试过滤的选择在查询链中较早出现联接时才会发生

# this works
my_select = select([tbl.c.id, tbl.c.my_col])
filtered = my_select.where(tbl.c.my_col == 'foo')

# this doesn't work, and seems to wrap the my_select in an additional subquery
j = tbl1.join(tbl2, tbl1.c.id == tbl2.c.id)
my_select = select([tbl1.c.id, tbl2.c.my_col]).select_from(j)
filtered = my_select.where(my_select.c.my_col == 'foo')

# Text representations will usually work as expected
j = tbl1.join(tbl2, tbl1.c.id == tbl2.c.id)
my_select = select([tbl1.c.id, tbl2.c.my_col]).select_from(j)
filtered = my_select.where("my_col = 'foo'")

Answer 1

我想我只是想通了。 问题似乎是自参考列，所以

filtered = my_select.where(my_select.c.my_col == 'foo')

应该是

filtered = my_select.where(tbl2.c.my_col == 'foo')

因此它引用的是原始列对象，而不是select中的列。

这只是一个假设，因此，如果有人也可以验证，将不胜感激。