feat: support different types for CompatReader

[KKould]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

#3517

What's changed and what's your intention?

Support CompatReader to be compatible with different types of reads (for modify column type)

Whether the type allows conversion will be verified in the next pr: (reference:
ModifyColumn::validate https://github.com/GreptimeTeam/greptimedb/pull/3701/files#diff-839e23ed322c90eacc42fdddeb1f7108335e6434eba0a7a1c6dbc42052a8b9e9)

Tips: Please closely 64FD8R166 in the cast in this line of code, the safe of the CastOptions it used by default is true, so it is guaranteed that the type is allowed to be transformed and specific When the value cannot be converted, set the value to null, e.g. type: String -> Integer, value: "1" -> 1, "hello" -> null

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR does not require documentation updates.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.28%. Comparing base (4437225) to head (089cd05).
Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3745      +/-   ##
==========================================
- Coverage   85.51%   85.28%   -0.24%     
==========================================
  Files         946      946              
  Lines      159555   160034     +479     
==========================================
+ Hits       136447   136482      +35     
- Misses      23108    23552     +444     

[KKould]

We can also set up a simple rule.

• fill NULL if the column is nullable
• fill default if the column is not null

#3517 (comment)

cast can only be converted to null but cannot set default. Do you have any suggestions on this?

[evenyag]

cast can only be converted to null but cannot set default. Do you have any suggestions on this?

Maybe we could only allow modifying the data type when the column is nullable or casting the type won't be fallible.

[evenyag]

Sorry for the slow review. Don't have enough time to review this last week.

[KKould]

Maybe we could only allow modifying the data type when the column is nullable or casting the type won't be fallible.

I added this check in pr: #3757 9003afc

casting the type won't be fallible

I think this is difficult to do. Because when conversion is allowed between certain types, the value may not necessarily be able to be converted. Of course, conversion between some types is definitely successful(to String), but judging by self will be relatively intrusive (and prone to bugs)

so I chose to check if column is allowed to be nullable

[evenyag]

Mostly LGTM

[evenyag]

LGTM

[waynexia]

LGTM. Thanks!

[v0y4g3r]

LGTM!