[quinnj]

SQL containing a NUL byte raised a confusing UndefVarError instead of the intended PostgresInterfaceError:

DBInterface.execute(conn, "SELECT 1\0")
# UndefVarError: `Postgres` not defined in `Postgres.API`

writepart in src/api/API.jl threw Postgres.PostgresInterfaceError(...), but the name Postgres is not bound inside module API. The module already imports PostgresInterfaceError, so the fix drops the prefix. The startup-parameter variant had the same mistake; it is normally unreachable because Connection rejects NUL bytes in its parameters first.

The check runs while the message is still in a local buffer, so nothing reaches the server and the connection stays usable. That was already true; only the error type was wrong.

Tests:

• A no-server testset checks both methods throw PostgresInterfaceError and write nothing.
• An integration assertion checks DBInterface.execute(conn, "SELECT 1\0") throws PostgresInterfaceError and the connection still answers SELECT 1.

Validation:

• The new testset fails on main (2 × UndefVarError) and passes with the fix.
• JET.report_package(Postgres; mode=:typo) reports exactly these two undefined references on main and none with the fix, so there are no others in the package.

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