Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Optimize the concat_ws function #3869

Merged
merged 2 commits into from
Oct 18, 2022

Conversation

HaoYang670
Copy link
Contributor

@HaoYang670 HaoYang670 commented Oct 18, 2022

Signed-off-by: remzi [email protected]

Which issue does this PR close?

Closes #3856.
Closes #3857.

Rationale for this change

Simplify the concat_ws expression:

  1. fold the whole expression to null if the delimiter is null
  2. filter out null arguments
  3. use concat to replace concat_ws if the delimiter is an empty string
  4. concatenate contiguous literals if the delimiter is a literal.

What changes are included in this PR?

Are there any user-facing changes?

Signed-off-by: remzi <[email protected]>
@github-actions github-actions bot added logical-expr Logical plan and expressions optimizer Optimizer rules labels Oct 18, 2022
Signed-off-by: remzi <[email protected]>
Copy link
Contributor

@alamb alamb left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is beautiful @HaoYang670

@@ -53,6 +53,12 @@ impl Literal for String {
}
}

impl Literal for &String {
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

"TIL" lit() 👍

Comment on lines +325 to +354
for arg in args {
match arg {
// filter out null args
Expr::Literal(ScalarValue::Utf8(None) | ScalarValue::LargeUtf8(None)) => {}
Expr::Literal(ScalarValue::Utf8(Some(v)) | ScalarValue::LargeUtf8(Some(v))) => {
match contiguous_scalar {
None => contiguous_scalar = Some(v.to_string()),
Some(mut pre) => {
pre += delimiter;
pre += v;
contiguous_scalar = Some(pre)
}
}
}
Expr::Literal(s) => return Err(DataFusionError::Internal(format!("The scalar {} should be casted to string type during the type coercion.", s))),
// If the arg is not a literal, we should first push the current `contiguous_scalar`
// to the `new_args` and reset it to None.
// Then pushing this arg to the `new_args`.
arg => {
if let Some(val) = contiguous_scalar {
new_args.push(lit(val));
}
new_args.push(arg.clone());
contiguous_scalar = None;
}
}
}
if let Some(val) = contiguous_scalar {
new_args.push(lit(val));
}
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This pattern of creating the contiguous scalar is so similar -- I wonder if it could be extracted out into a function -- perhaps as a follow on PR

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Thank you for reviewing @alamb ♥️

The logic for concat and concat_ws is a little different, because in concat_ws we must consider the delimiter and we can't ignore the empty string literals. I will try to find a way to refactor them.

args: new_args,
}
}
} => simpl_concat(args)?,
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

❤️

// the delimiter is not a literal
{
let expr = concat_ws(col("c"), vec![lit("a"), null.clone(), lit("b")]);
let expected = concat_ws(col("c"), vec![lit("a"), lit("b")]);
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

so cool!

@andygrove
Copy link
Member

Thanks @HaoYang670

@andygrove andygrove merged commit feff5dc into apache:master Oct 18, 2022
@HaoYang670 HaoYang670 deleted the 3856_3857_optimize_concat_ws branch October 19, 2022 01:12
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
logical-expr Logical plan and expressions optimizer Optimizer rules
Projects
None yet
3 participants