It was a mistake to use it in other contexts. This made interop
difficult between pacakges that depended on pgtype such as pgx and
packages that did not like pgconn and pgproto3. In particular this was
awkward for prepared statements.
This is preparation for removing pgx.PreparedStatement in favor of
pgconn.PreparedStatement.
This is in preparation for a Begin / Tx interface that will similate
nested transactions with savepoints.
In addition, this passes the TxOptions struct by value and thereby
removes an allocation.
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.
A batch on a tx object does not open and close a transaction itself and
instead use the tx object to ensure the transactionality of the batch
remove unused boolean 'sent' in batch struct
An incompletely read select followed by an insert would fail. This was
caused by query methods in the non-batch path always calling
ensureConnectionReadyForQuery. This ensures that connections interrupted
by context cancellation are still usable. However, in the batch case
query methods are not being called while reading the result. A
incompletely read select followed by another select would not manifest
this error due to it starting by reading until row description. But when
an incomplete select (which even a successful QueryRow would be
considered) is followed by an Exec, the CommandComplete message from the
select would be considered as the response to the subsequent Exec.
The fix is the batch tracking whether a CommandComplete is pending and
reading it before advancing to the next result. This is similar in
principle to ensureConnectionReadyForQuery, just specific to Batch.
