feat(parser): support emit_mode

[TennyZhuang]

Signed-off-by: TennyZhuang [email protected]

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What's changed and what's your intention?

The parser part

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features).
• I have demonstrated that backward compatibility is not broken by breaking changes and created issues to track deprecated features to be removed in the future. (Please refer the issue)
• All checks passed in ./risedev check (or alias, ./risedev c)

Refer to a related PR or issue link (optional)

#6042

[codecov]

Codecov Report

Merging #7783 (923b6ca) into main (2d79894) will decrease coverage by 0.02%.
The diff coverage is 70.58%.

@@            Coverage Diff             @@
##             main    #7783      +/-   ##
==========================================
- Coverage   71.74%   71.73%   -0.02%     
==========================================
  Files        1107     1107              
  Lines      176388   176422      +34     
==========================================
+ Hits       126558   126564       +6     
- Misses      49830    49858      +28     

Flag	Coverage Δ
rust	71.73% <70.58%> (-0.02%)	⬇️

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

Impacted Files	Coverage Δ
src/sqlparser/src/keywords.rs	100.00% <ø> (ø)
src/frontend/src/handler/mod.rs	61.35% <37.50%> (-0.79%)	⬇️
src/sqlparser/src/parser.rs	91.94% <70.58%> (-0.14%)	⬇️
src/sqlparser/src/ast/mod.rs	88.88% <100.00%> (+0.08%)	⬆️
src/batch/src/executor/group_top_n.rs	68.23% <0.00%> (-6.48%)	⬇️
src/meta/src/hummock/mock_hummock_meta_client.rs	63.95% <0.00%> (-0.51%)	⬇️
src/batch/src/task/task_execution.rs	51.62% <0.00%> (-0.51%)	⬇️
src/object_store/src/object/mem.rs	86.48% <0.00%> (-0.39%)	⬇️
src/storage/src/hummock/compactor/iterator.rs	97.95% <0.00%> (-0.30%)	⬇️
src/storage/src/hummock/sstable_store.rs	64.57% <0.00%> (-0.16%)	⬇️
... and 1 more

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[BugenZhao]

LGTM

[fuyufjh]

I thought it should be part of the query i.e. inside the SELECT ... clause. Did we change our mind?

[TennyZhuang]

If we defined them on SELECT, what's the semantic on subquery or CTE?

Currently, our conclusion is that we should ensure a mview or a sink can only have one emit option, the only way is defined on view.

[fuyufjh]

risingwavelabs/rfcs#30 defines the semantics in terms of relational algebra (i.e. given input set, what should be the output set), so the semantics is still well-defined for subqueries or CTEs.