alamb commented on code in PR #6369:
URL: https://github.com/apache/arrow-datafusion/pull/6369#discussion_r1196977982
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datafusion/optimizer/src/simplify_expressions/regex.rs:
##########
@@ -130,6 +139,46 @@ fn is_safe_for_like(c: char) -> bool {
(c != '%') && (c != '_')
}
+/// returns true if the elements in a `Concat` pattern are:
+/// - `[Look::Start, Look::End]`
+/// - `[Look::Start, Literal(_), Look::End]`
+fn is_anchored_literal(v: &[Hir]) -> bool {
+ match v.len() {
+ 2..=3 => (),
+ _ => return false,
+ };
+
+ let first_last = (
+ v.first().expect("length checked"),
+ v.last().expect("length checked"),
+ );
+ if !matches!(first_last,
+ (s, e) if s.kind() == &HirKind::Look(Look::Start)
+ && e.kind() == &HirKind::Look(Look::End)
+ )
+ {
+ return false;
+ }
+
+ v.iter()
+ .skip(1)
+ .take(v.len() - 2)
+ .all(|h| matches!(h.kind(), HirKind::Literal(_)))
+}
+
+/// extracts a string literal expression assuming that [`is_anchored_literal`]
+/// returned true.
+fn anchored_literal_to_expr(v: &[Hir]) -> Option<Expr> {
+ match v.len() {
+ 2 => Some(lit("")),
+ 3 => {
+ let HirKind::Literal(l) = v[1].kind() else { return None };
+ str_from_literal(l).map(lit)
+ }
+ _ => None,
+ }
+}
+
fn lower_simple(mode: &OperatorMode, left: &Expr, hir: &Hir) -> Option<Expr> {
println!("Considering hir kind: mode {mode:?} hir: {hir:?}");
Review Comment:
I noticed this stray `println` while reviewing this code so I propose
removing it: https://github.com/apache/arrow-datafusion/pull/6375
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