1. Michael Bayer
  2. sqlalchemy
  3. Issues

Issues

Issue #3161 invalid

Support partial unique constrains on PostgreSQL

Jonathan Stoppani
created an issue

This is already supported for normal indexes, but if I try to pass the postgresql_where keyword arg to UniqueConstraint, it fails with the following error:

sqlalchemy.exc.ArgumentError: Argument 'postgresql_where' is not accepted by dialect 'postgresql' on behalf of <class 'sqlalchemy.sql.schema.UniqueConstraint'>

Comments (8)

  1. Michael Bayer repo owner

    okey doke this would be the "def visit_unique_constraint(self, constraint):" added to sqlalchemy/dialects/postgresql/base.py->PGDDLCompiler, adapted from sqlalchemy/sql/compiler.py->DDLCompiler, the other mechanics of "postgresql_where" would be set up as they are for indexes, e.g. the PGDialect.construct_arguments collection. Tests would be straight compile tests in test/dialect/postgresql/test_compiler.py -> CompilerTest, there are some Index tests there now that can be emulated.

    In absence of this feature you can use DDL() of course, otherwise pullreqs via github are preferred in case you have an interest :).

  2. Stephen J Fuhry

    Michael Bayer I spent some time looking into this this morning, and I think that this is an invalid request. Postgres does not support partial UNIQUE CONSTRAINTs. It does, however, support partial UNIQUE INDEXes - a feature which SQLAlchemy supports correctly today.

    Jonathan Stoppani I believe the functionality you're looking for can be found by changing UniqueConstraint to Index, and simply adding a unique=True. See:

    Index.init

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