feat: Optimize CASE expression for usage where then and else values are literals #11553
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| .unwrap_or_else(|_| Arc::clone(e)); | ||
| let else_ = Scalar::new(expr.evaluate(batch)?.into_array(1)?); | ||
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| Ok(ColumnarValue::Array(zip(&when_value, &then_value, &else_)?)) |
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if the input is ColumnarValue::Scalar shouldn't the output also be a ColumnarValue::Scalar (rather than a ColumnarValue::Array?)
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No, the output will be an array containing values based on two scalar arguments.
SELECT CASE WHEN a > 2 THEN 'even' ELSE 'odd' END FROM foo
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odd
even
even
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I wonder if it would make sense (in a separate PR) to produce a dictionary array in this case since it will only even contain two distinct values? 🤔
| @@ -50,3 +50,19 @@ SELECT CASE WHEN a > 2 THEN b END FROM foo | |||
| NULL | |||
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| 6 | |||
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| # scalar or scalar (string) | |||
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Could you also add a test where both arguments are scalars (like CASE WHEN 1 > 2 THEN 'true' ELSE 'false') ?
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| # scalar or scalar (string) | ||
| query T | ||
| SELECT CASE WHEN a > 2 THEN 'even' ELSE 'odd' END FROM foo |
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Looks like NULL handling in this specialized implementation is not tested, we can add a (NULL, NULL) row into foo table
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Good point. I have added this.
…re literals (apache#11553) * Optimize CASE expression for usage where then and else values are literals * add slt test * add more test cases
Which issue does this PR close?
N/A
Rationale for this change
What changes are included in this PR?
Add a fast path for a specific usage of CASE expression
Are these changes tested?
Are there any user-facing changes?