alamb commented on code in PR #4115:
URL: https://github.com/apache/arrow-datafusion/pull/4115#discussion_r1015485753
##########
datafusion/proto/src/to_proto.rs:
##########
@@ -455,11 +455,36 @@ impl TryFrom<&Expr> for protobuf::LogicalExprNode {
}
}
Expr::BinaryExpr(BinaryExpr { left, op, right }) => {
- let binary_expr = Box::new(protobuf::BinaryExprNode {
- l: Some(Box::new(left.as_ref().try_into()?)),
- r: Some(Box::new(right.as_ref().try_into()?)),
+ // Try to linerize a nested binary expression tree of the same
operator
Review Comment:
Is it correct that this code will work for `(((A AND B) AND C) AND D)` but
not `A AND (B AND (C AND D)))`?
##########
datafusion/proto/src/bytes/mod.rs:
##########
@@ -332,7 +361,8 @@ mod test {
println!("testing: {n}");
let expr_base = col("a").lt(lit(5i32));
- let expr = (0..n).fold(expr_base.clone(), |expr, _|
expr.and(expr_base.clone()));
+ // Generate a tree of AND and OR expressions (no subsequent
ANDs or ORs).
Review Comment:
I would love to see a test that made the other type of nesting
`(expr_base.clone().and(expr))`
##########
datafusion/proto/src/from_proto.rs:
##########
@@ -690,11 +690,34 @@ pub fn parse_expr(
.ok_or_else(|| Error::required("expr_type"))?;
match expr_type {
- ExprType::BinaryExpr(binary_expr) =>
Ok(Expr::BinaryExpr(BinaryExpr::new(
- Box::new(parse_required_expr(&binary_expr.l, registry, "l")?),
- from_proto_binary_op(&binary_expr.op)?,
- Box::new(parse_required_expr(&binary_expr.r, registry, "r")?),
- ))),
+ ExprType::BinaryExpr(binary_expr) => {
+ let op = from_proto_binary_op(&binary_expr.op)?;
+ let operands = binary_expr
+ .operands
+ .iter()
+ .map(|expr| parse_expr(expr, registry))
+ .collect::<Result<Vec<_>, _>>()?;
+
+ if operands.len() < 2 {
+ return Err(proto_error(
+ "A binary expression must always have at least 2 operands",
+ ));
+ }
+
+ // Reduce the linearized operands (ordered by left innermost to
right
+ // outermost) into a single expression tree.
+ Ok(operands
+ .into_iter()
+ .reduce(|left, right| {
+ Expr::BinaryExpr(BinaryExpr::new(Box::new(left), op,
Box::new(right)))
+ })
+ .unwrap_or_else(|| {
+ // As long as we have the bounds check above, this should
never happen.
+ panic!(
Review Comment:
I think the comment is clear that this "should not happen" and thus I
believe the `panic` is fine
You could also write this same logic slightly more concisely as
`expect("Binary expression could not be reduced to a single expression.")`
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