Also remove PrepareEx. It's primary usage was for context. Supplying
parameter OIDs is unnecessary when you can type cast in the query SQL.
If it does become necessary or desirable to add options back it can be
added in a backwards compatible way by adding a varargs as last
argument.
Instead of needing to instrospect the database on connection preload the
standard OID / type map. Types from extensions (like hstore) and custom
types can be registered by the application developer. Otherwise, they
will be treated as strings.
It is impossible to guarantee that the a query executed with the simple
protocol will behave the same as with the extended protocol. This is
because the normal pgx path relies on knowing the OID of query
parameters. Without this encoding a value can only be determined by the
value instead of the combination of value and PostgreSQL type. For
example, how should a []int32 be encoded? It might be encoded into a
PostgreSQL int4[] or json.
Removal also simplifies the core query path.
The primary reason for the simple protocol is for servers like PgBouncer
that may not be able to support normal prepared statements. After
further research it appears that issuing a "flush" instead "sync" after
preparing the unnamed statement would allow PgBouncer to work.
The one round trip mode can be better handled with prepared statements.
As a last resort, all original server functionality can still be accessed by
dropping down to PgConn.
Previously, a failed connection could be put back in a pool and when the
next query was attempted it would fail immediately trying to prepare the
query or reset the deadline. It wasn't clear if the Query or Exec call
could safely be retried since there was no way to know where it failed.
You can now call LastQuerySent and if it returns false then you're
guaranteed that the last call to Query(Ex)/Exec(Ex) didn't get far enough
to attempt to send the query. The call can be retried with a new
connection.
This is used in the stdlib to return a ErrBadConn if a network error
occurred and the statement was not attempted.
Fixes#427
It's possible to define a type (e.g., an enum) with the same name in two
different schemas. When initializing data types after connecting, types
defined within schemas other than pg_catalog or public should be
qualified with their schema name to disambiguate them and ensure all
types with the same base name get added to the map of OID to type.
Prior to this commit, the last type scanned would "win", and all others
with the same name would be missing from the ConnInfo type maps, which
would subsequently cause any PREPARE involving columns of those missing
types to return the error "unknown oid".
