Feat: Update partitioning by DATE, DATETIME, TIMESTAMP, _PARTITIONDATE

[chalmerlowe]

This adds some additional functionality to properly handle partitioning of columns with the following datatypes.

• DATE
• TIMESTAMP
• DATETIME
• _PARTITIONDATE

Where appropriate, ensures the following functions can be used with/or without the following TimePartitioningTypes (HOUR, DAY, MONTH, YEAR).

• DATE_TRUNC()
• TIMESTAMP_TRUNC()
• DATETIME_TRUNC()
• DATE()

This is a nearly complete fix for #1072. The table from #1072 is included here:
NOTE: This PR does not handle _PARTITIONTIME

Column Data Type	HOUR	DAY	MONTH	YEAR
DATE	N/A	Fixed by #1057	via DATE_TRUNC	via DATE_TRUNC
DATETIME	Incorrectly implemented via DATE_TRUNC TODO: use  DATETIME_TRUNC	Incorrectly implemented via DATE_TRUNC TODO: use  DATETIME_TRUNC	Incorrectly implemented via DATE_TRUNC TODO: use  DATETIME_TRUNC	Incorrectly implemented via DATE_TRUNC TODO: use  DATETIME_TRUNC
TIMESTAMP	via TIMESTAMP_TRUNC	via TIMESTAMP_TRUNC	via TIMESTAMP_TRUNC	via TIMESTAMP_TRUNC
_PARTITIONDATE	N/A	via DATE_TRUNC	via DATE_TRUNC	via DATE_TRUNC
_PARTITIONTIME	Not currently implemented TODO: USE TIMESTAMP_TRUNC	Not currently implemented TODO: USE TIMESTAMP_TRUNC	Not currently implemented TODO: USE TIMESTAMP_TRUNC	Not currently implemented TODO: USE TIMESTAMP_TRUNC

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[suzmue]

field == "_PARTITIONDATE" is always true

[suzmue]

I'm a little confused, the type isn't passed to the trunc_fn, should it be?

[suzmue]

There are a lot of cases here that make this function hard to parse. In particular, I think it could be improved if instead of the first special casing for time.partitioning.field is None block was instead combined by deleting that check, and moving the if time.partioning.type_ in ... below the if field is not None block:

        field = "_PARTITIONDATE"
        trunc_fn = "DATE_TRUNC"
        if time_partitioning.field is not None:
            field = time_partitioning.field

            if isinstance(
                table.columns[field].type,
                (sqlalchemy.sql.sqltypes.TIMESTAMP),
            ):
                trunc_fn = "TIMESTAMP_TRUNC"
            elif isinstance(
                table.columns[field].type,
                sqlalchemy.sql.sqltypes.DATETIME,
            ):
                  trunc_fn = "DATETIME_TRUNC"



        if trunc_fn == "DATE_TRUNC" and not time_partitioning.type_ in {"DAY", "MONTH", "YEAR"}:
               raise ValueError(
                      f"DATE_TRUNC can only be used with TimePartitioningTypes {{DAY, MONTH, YEAR}} received {time_partitioning.type_}"
                  )

        # Format used with generically with DATE, TIMESTAMP, DATETIME, DATE_TRUNC
        return f"PARTITION BY {trunc_fn}({field}, {time_partitioning.type_})"**

[suzmue]

I had removed the the last if isinstance(table.columns[field].type,, because I thought it was part of the if elif, I see now that its separate. If thats the case, it could be the first if condition so it can take priority instead of setting it back after the fact (pattern matching would be nice here when we support >= python 3.10)