chore: fix datafusion-spark substring

comphead · comphead · commit c36d89519a76 · 2026-04-30T09:11:13.000-07:00
diff --git a/datafusion/spark/src/function/string/substring.rs b/datafusion/spark/src/function/string/substring.rs
@@ -166,8 +166,7 @@ fn spark_start_to_datafusion_start(start: i64, len: usize) -> i64 {
         start.max(1)
     } else {
         let len_i64 = i64::try_from(len).unwrap_or(i64::MAX);
-        let start = start.saturating_add(len_i64).saturating_add(1);
-        start.max(1)
+        start + len_i64 + 1
     }
 }
 
diff --git a/datafusion/sqllogictest/test_files/spark/string/substring.slt b/datafusion/sqllogictest/test_files/spark/string/substring.slt
@@ -146,7 +146,7 @@ ark SQL
 (empty)
 (empty)
 (empty)
-Spa
+(empty)
 NULL
 NULL
 NULL
@@ -197,7 +197,14 @@ ark SQL
 (empty)
 (empty)
 (empty)
-Spa
+(empty)
 NULL
 NULL
 NULL
+
+query T
+SELECT substr(column1, -10, 3)
+FROM VALUES
+('abc'::string)
+----
+(empty)

Original file line number	Diff line number	Diff line change
`@@ -166,8 +166,7 @@ fn spark_start_to_datafusion_start(start: i64, len: usize) -> i64 {`
`166`	`166`	`start.max(1)`
`167`	`167`	`} else {`
`168`	`168`	`let len_i64 = i64::try_from(len).unwrap_or(i64::MAX);`
`169`		`- let start = start.saturating_add(len_i64).saturating_add(1);`
`170`		`- start.max(1)`
	`169`	`+ start + len_i64 + 1`
`171`	`170`	`}`
`172`	`171`	`}`
`173`	`172`