LucaCappelletti94 commented on code in PR #2352:
URL:
https://github.com/apache/datafusion-sqlparser-rs/pull/2352#discussion_r3317319913
##########
src/parser/mod.rs:
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@@ -1717,6 +1731,23 @@ impl<'a> Parser<'a> {
return prefix;
}
+ // Memoize parse_prefix failures to break 2^N speculation when both
+ // prefix arms fail at every level (e.g. `IF(current_time(...x`).
+ // The per-arm cache in `parse_prefix_inner` complements this for
+ // chains where the reserved arm fails but the unreserved fallback
+ // succeeds (e.g. `case-case-...c`).
+ let start_index = self.index;
+ if let Some(cached) = self.failed_prefix_positions.get(&start_index) {
+ return Err(cached.clone());
+ }
+ let result = self.parse_prefix_inner();
+ if let Err(ref e) = result {
+ self.failed_prefix_positions.insert(start_index, e.clone());
Review Comment:
I am not sure I follow, currently the runtime is exponential, so the parser
is just failing on these inputs. With the fix, the time requirement becomes
linear and the the memory requirements remain linear with input size even for
pathological cases
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