such that they are matched to the received result set positionally,
rather than by name.  Originally, this was seen as a way to handle
cases where we had columns returned with difficult-to-predict names,
though in modern use that issue has been overcome by anonymous
labeling.   In this version, the approach basically reduces function
call count per-result by a few dozen calls, or more for larger
sets of result columns.  The approach still degrades into a modern
version of the old approach if textual elements modify the result
map, or if any discrepancy in size exists between
the compiled set of columns versus what was received, so there's no
issue for partially or fully textual compilation scenarios where these
lists might not line up.  fixes #918
- callcounts still need to be adjusted down for this so zoomark
tests won't pass at the moment

as :class:`.TypeDecorator` objects.

dialect on a type where MySQL does not support CAST; MySQL only
supports CAST on a subset of datatypes.   SQLAlchemy has for a long
time just omitted the CAST for unsupported types in the case of
MySQL.  While we don't want to change this now, we emit a warning
to show that it's taken place.   A warning is also emitted when
a CAST is used with an older MySQL version (< 4) that doesn't support
CAST at all, it's skipped in this case as well.
fixes #3237

For versions > 1.10.1 pg8000 returns de-serialized JSON objects rather
than a string. SQL parameters are still strings though.

pg8000 uses Versioneer, which means that development versions have
version strings that don't fit into the dotted triple number format.
Released versions will always fit the triple format though.

The pg8000 dialect now supports the setting of the PostgreSQL parameter
client_encoding from create_engine().

and regexp parsing of SQL in order to form a complete picture of
constraints + their names.  fixes #3244 fixes #3261
- factor various PRAGMA work to be centralized into one call