Render date literals as strings in time range filters

[tlento]

MetricFlow's rendering has historically cast date literals to
the underlying engine type in date range comparison filters, so
if a user passed in a start_time of 2021-01-01 and an end_time
of 2021-01-31 we would render something like:

WHERE ds BETWEEN CAST('2021-01-01' AS TIMESTAMP) AND CAST('2021-01-31' AS TIMESTAMP)

This turns out to cause problems with time partition columns, because
they typically only apply pruning to literal predicates - any value
processed by a CAST function prevents pruning from kicking in, as the
engine takes the appropriately conservative approach of doing full
row-by-row comparisons between the cast output and the partition value.

In researching this issue two things became clear:

1. We need a holistic answer to ensuring engines apply partition
   pruning, one which is beyond the scope of this change.
2. We can solve part of the problem by removing the CAST call
   in time range filters based on literal value inputs.

It turns out every engine we support does implicit type coercion
between string values and date/time types. This means we don't have
to care what the appropriate time type column might be in this case,
because the standard behavior is to simply do the comparison correctly
regardless of underlying partition column type.

This change simple removes the CAST calls from this particular rendering
block, which should enable users to at least run queries that will do
some level of pruning, even if the solution is incomplete with respect
to the types of time partition columns it can address.

Note that we assume all engines accept and convert from ISO-standard
date strings, but this is not a change from the prior behavior, which
assumed the same thing but wrapped it in a CAST function call.

[tlento]

Current dependencies on/for this PR:

• main
  • PR Update Pandas dependency to 1.5.x #719
    • PR Loosen version pins for MetricFlow dependencies #720
      • PR Make test execution more consistent and convenient #721
        • PR Remove EnvironmentVariable helper class #722
          • PR Render date literals as strings in time range filters #724 👈

This comment was auto-generated by Graphite.

[plypaul]

As I recall, this was put in due to an issue with a previously supported engine.

[tlento]

As I recall, this was put in due to an issue with a previously supported engine.

That's what I remember too but I can't find any evidence of it. It's possible the offending engine has updated their type handling. It's also possible we didn't understand BigQuery's coercion logic - their documentation on this is hidden well enough that it appears BigQuery simply doesn't support it, but they do (and they have to because of the way their partition pruning works).