Thanks for the pointers and for checking. I misidentified the problem in traverse. It does eventually iterate down to just the columns in the call to _copy_internals. So the problem boils down to the second thing I mentioned which is the require_embedded parameter being set to true when corresponding_column is called. The selectable I'm using isn't just a simple alias.
I subclassed ClauseAdapter and rewrote replace so that corresponding_column is called with require_embedded=False (https://github.com/zzzeek/sqlalchemy/blob/699272e4dcb9aa71ebbc0d9487fb6de82d3abc2b/lib/sqlalchemy/sql/util.py#L656). This seems to be working. On Wednesday, May 9, 2018 at 12:28:28 AM UTC-7, Zac Goldstein wrote: > > I'm trying to use ClauseAdapter.traverse similar to how it's used in your > old blog post to substitute columns in arbitrary clauses with columns on a > different selectable that share an ancestor: > http://techspot.zzzeek.org/archive/2008/01/1/ > > Even in a simple case using a BinaryExpression, > ClauseAdapter(selectable).traverse(binaryexpression) is simply returning > the expression. When I looked at it with the debugger, it seems the > expression isn't being traversed, but rather it eventually feeds the entire > BinaryExpression object into corresponding_column and subsequently > returns the full expression since obviously the BinaryExpression can't be > matched to a particular column on the selectable. > > selectable.corresponding_column(binaryexpression.left) returns the > correct column, however > ClauseAdapter(selectable).traverse(binaryexpression.left) does not. The > discrepancy is found in corresponding_column being called with > require_embedded=True during traverse, which is hardcoded. I don't know > if this behavior causes the behavior I previously described with the > BinaryExpression being passed to corresponding_column, but it seemed > noteworthy. > > Any ideas for fixes or alternatives? > > Thanks > > > > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
