alamb commented on code in PR #5816:
URL: https://github.com/apache/arrow-datafusion/pull/5816#discussion_r1155932650
##########
datafusion/optimizer/src/simplify_expressions/expr_simplifier.rs:
##########
@@ -2210,6 +2222,68 @@ mod tests {
assert_eq!(simplify(expr_eq), lit(true));
}
+ #[test]
+ fn test_simplify_log() {
+ // Log(c3, 1) ===> 0
+ {
+ let expr = log(col("c3_non_null"), lit(1));
+ let expected = lit(0i64);
+ assert_eq!(simplify(expr), expected);
+ }
+ // Log(c3, c3) ===> 1
+ {
+ let expr = log(col("c3_non_null"), col("c3_non_null"));
+ let expected = lit(1i64);
+ assert_eq!(simplify(expr), expected);
+ }
+ // Log(c3, Power(c3, c4)) ===> c4
+ {
+ let expr = log(
+ col("c3_non_null"),
+ power(col("c3_non_null"), col("c4_non_null")),
+ );
+ let expected = col("c4_non_null");
+ assert_eq!(simplify(expr), expected);
+ }
+ // Log(c3, c4) ===> c4
Review Comment:
```suggestion
// Log(c3, c4) ===> Log(c3, c4)
```
##########
datafusion/optimizer/src/simplify_expressions/utils.rs:
##########
@@ -350,6 +351,73 @@ pub fn distribute_negation(expr: Expr) -> Expr {
}
}
+/// Simplify the `log` function by the relevant rules:
+/// 1. Log(a, 1) ===> 0
+/// 2. Log(a, a) ===> 1
+/// 3. Log(a, Power(a, b)) ===> b
Review Comment:
I think this is a good set of changes for now.
##########
datafusion/optimizer/src/simplify_expressions/expr_simplifier.rs:
##########
@@ -1072,6 +1072,18 @@ impl<'a, S: SimplifyInfo> TreeNodeRewriter for
Simplifier<'a, S> {
out_expr.rewrite(self)?
}
+ // log
Review Comment:
I agree splitting it into smaller modules would be a great idea for a follow
on PR
##########
datafusion/common/src/scalar.rs:
##########
@@ -1723,6 +1745,27 @@ impl ScalarValue {
})
}
+ pub fn new_ten(datatype: &DataType) -> Result<ScalarValue> {
Review Comment:
It sounds like a reasonable idea. Thanks @izveigor
It might be possible to to use the traits defined in arrow-rs for this:
https://docs.rs/arrow/latest/arrow/array/trait.ArrowPrimitiveType.html
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