feat(expr): support cast from number to varchar

[xiaoyong-z]

Signed-off-by: xyz [email protected]

What's changed and what's your intention?

add support from number[int16/int32/int64/float32/float64/decimal] to varchar using to_string method

PLEASE DO NOT LEAVE THIS EMPTY !!!

Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests

Refer to a related PR or issue link (optional)

#112

[fuyufjh]

LGTM

[BugenZhao]

Thanks for your contribution! It seems we can also replace bool_to_str with general_to_string now?

[TennyZhuang]

clippy failed

error: casting float literal to `f32` is unnecessary
[452](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:452)
   --> src/expr/src/vector_op/cast.rs:277:38
[453](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:453)
    |
[454](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:454)
277 |         assert_eq!(general_to_string(32.12 as f32).unwrap(), "32.12");
[455](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:455)
    |                                      ^^^^^^^^^^^^ help: try: `32.12_f32`
[456](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:456)
    |
[457](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:457)
    = note: `-D clippy::unnecessary-cast` implied by `-D warnings`
[458](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:458)
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
[459](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:459)

[460](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:460)
error: casting float literal to `f32` is unnecessary
[461](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:461)
   --> src/expr/src/vector_op/cast.rs:278:38
[462](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:462)
    |
[463](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:463)
278 |         assert_eq!(general_to_string(-32.14 as f32).unwrap(), "-32.14");
[464](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:464)
    |                                      ^^^^^^^^^^^^^ help: try: `-32.14_f32`
[465](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:465)
    |
[466](https://github.com/singularity-data/risingwave/runs/6445857930?check_suite_focus=true#step:9:466)
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast

[BugenZhao]

LGTM!

[codecov]

Codecov Report

Merging #2522 (8692480) into main (6b7d5b7) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2522      +/-   ##
==========================================
+ Coverage   72.17%   72.18%   +0.01%     
==========================================
  Files         674      674              
  Lines       87831    87853      +22     
==========================================
+ Hits        63395    63421      +26     
+ Misses      24436    24432       -4     

Flag	Coverage Δ
rust	72.18% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/expr/src/expr/expr_unary.rs	75.97% <ø> (ø)
src/expr/src/vector_op/cast.rs	59.88% <100.00%> (+9.21%)	⬆️
src/meta/src/model/barrier.rs	78.57% <0.00%> (-3.58%)	⬇️
src/meta/src/stream/stream_manager.rs	63.86% <0.00%> (-0.15%)	⬇️
src/common/src/types/decimal.rs	82.25% <0.00%> (+0.26%)	⬆️

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more