python - sqlalchemy core autoincrement integer column which is part of the unique constraint -

requirement: composite key having auto-incremental value. how define table:

    doc_versions = table("doc_versions", metadata,                          column("id", integer, primary_key=true),                          column("doc_id", integer,foreignkey("docs.id")),                          column("version_number", integer, default=select([                     func.max(1, 1)])),                          uniqueconstraint("doc_id","version_number",                                           name="doc_version")                          ) 

how initialize version number composite key i.e doc_id + version_number should unique , take next sequence. want use sqlalchemy core 1.0.8

there have been lot of questions similar problems here, , answer (sorry no links, search e.g. 'sqlalchemy autoincrement composite'):

sqlalchemy can handle autoincrement on integer primary keys.

it's sad, true. can query table ordered doc_id , version_number, last row, , increment it. i'm using same method composite keys.