adriangb commented on code in PR #12978:
URL: https://github.com/apache/datafusion/pull/12978#discussion_r1805420707
##########
datafusion/core/src/physical_optimizer/pruning.rs:
##########
@@ -1610,6 +1625,93 @@ fn build_statistics_expr(
Ok(statistics_expr)
}
+fn extract_string_literal(expr: &Arc<dyn PhysicalExpr>) -> Result<&String> {
+ if let Some(lit) = expr.as_any().downcast_ref::<phys_expr::Literal>() {
+ if let ScalarValue::Utf8(Some(s)) = lit.value() {
+ return Ok(s);
+ }
+ }
+ plan_err!("LIKE expression must be a string literal")
+}
+
+fn extract_like_string_literal_prefix(
+ expr: &Arc<dyn PhysicalExpr>,
+) -> Result<Arc<phys_expr::Literal>> {
+ let s = extract_string_literal(expr)?;
+ let mut split_literal = s.split('%');
+ let prefix = split_literal.next().unwrap_or("");
+ // if the prefix is empty, return true
+ if prefix.is_empty() {
+ return plan_err!("Empty prefix in LIKE expression");
+ }
+ Ok(Arc::new(phys_expr::Literal::new(ScalarValue::Utf8(Some(
+ prefix.to_string(),
+ )))))
+}
+
+fn build_like_match(
+ expr_builder: &mut PruningExpressionBuilder,
+) -> Result<Arc<dyn PhysicalExpr>> {
+ // column LIKE literal => (min, max) LIKE literal split at % => min <=
split literal && split literal <= max
Review Comment:
Right that's the point, by splitting it at the first `%` we are able to
apply the same rules as equality:
```
column LIKE literal -> (min, max) LIKE (literal split at %) -> min <= split
literal && split literal <= max
vs
column = literal -> (min, max) = literal -> min <= literal && literal <= max
```
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