Minor: support complex expr as the arg in the ApproxPercentileCont function

[liukun4515]

Which issue does this PR close?

Closes #.

Rationale for this change

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

[alamb]

Thanks @liukun4515 -- this PR seems to fix the problem and has a test so 👍

This doesn't seem like it is a problem that is specific to approx_percentile_cont -- there might be a way to make it more general but we could also always do that as a follow on PR

[alamb]

I think this may be related to aliasing rather than simply complex expressions

❯ create table t (x int) as values (1), (2);
0 rows in set. Query took 0.001 seconds.

❯ select APPROX_PERCENTILE_CONT(x,  cast(1 as double)) from t;
+--------------------------------------+
| APPROX_PERCENTILE_CONT(t.x,Int64(1)) |
+--------------------------------------+
| 2                                    |
+--------------------------------------+
1 row in set. Query took 0.002 seconds.

However, I couldn't express the same alias using SQL.

I wonder if the expression simplifier code could be generalized to handle this case, so it applied to all arguments, not just the arguments to APPROX_PERCENTILE_CONT 🤔

[liukun4515]

yes, the rule of simplfy_expression can not handle the alisa expr.
But the cast(1 as float) will be simplified.
I think this is the diff between the cast and alisa

[liukun4515]

Thanks @liukun4515 -- this PR seems to fix the problem and has a test so 👍

This doesn't seem like it is a problem that is specific to approx_percentile_cont -- there might be a way to make it more general but we could also always do that as a follow on PR

Yes this pr is a quick fix for the issue.

We can enchancement the rule of simplified_expression to get this.