PREPARE TRANSACTION $1 causes a parse error

[Mathieu Fenniak]

In SQLAlchemy's engine.transaction.TLTransactionTest.testtwophasetransaction, the following appears to be being executed:

  cursor.execute("PREPARE TRANSACTION %(tid)s", {"tid": "..."})

which results in a PostgreSQL database error:

  ERROR 42601 'syntax error at or near "$1"'

Suggesting that a bind parameter cannot be used in PREPARE TRANSACTION.

[Mathieu Fenniak (mfenniak)]

PostgreSQL only supports a constant string in PREPARE TRANSACTION (as well as number of other places), and not a bind parameter. Therefore this will be documented as a known issue, and must be handled client-side (or part of a library like SQLAlchemy).