feat(rust,python,cli): add SQL support for timestamp precision modifier

[alexander-beedie]

Adds recognition of PostgreSQL compatible timestamp precision¹ modifier.
Supports values that map to our Datetime time units, specifically 3 → 'ms', 6 → 'us', 9 → 'ns':

Example

from datetime import datetime
import polars as pl

df = pl.DataFrame({
    "ts": [
        datetime(2024, 1, 7, 1, 2, 3, 123456),
        datetime(1999, 1, 1, 23, 59, 59, 555555),
        datetime(2020, 12, 30, 10, 30, 45, 987654),
    ],
})

with pl.SQLContext(frame_data=df, eager_execution=True) as ctx:
    print(ctx.execute(
        f"SELECT ts::timestamp(3) FROM frame_data")
    )
    # shape: (3, 1)
    # ┌─────────────────────────┐
    # │ ts                      │
    # │ ---                     │
    # │ datetime[ms]            │  << precision 3 → 'ms'
    # ╞═════════════════════════╡
    # │ 2024-01-07 01:02:03.123 │
    # │ 1999-01-01 23:59:59.555 │
    # │ 2020-12-30 10:30:45.987 │
    # └─────────────────────────┘

Footnotes

1. https://www.postgresql.org/docs/current/datatype-datetime.html ↩

[ritchie46]

idem.

[alexander-beedie]

Fixed all of these (and a further 20 or so after searching for them!) 👌

Related; I'll introduce a dedicated PolarsSQLError in a subsequent PR as it'll be useful to distinguish SQL-specific errors from engine/other ones 🤔