Wire PPL string scalar functions with analytics-backend-datafusion (opensearch-project#21543)

Signed-off-by: Tanik Pansuriya <panbhai@amazon.com>

Author: tanik98

sandbox/libs/analytics-framework/src/main/java/org/opensearch/analytics/spi/ScalarFunction.java

@@ -56,6 +56,7 @@ public enum ScalarFunction {
     UPPER(Category.STRING, SqlKind.OTHER_FUNCTION),
     LOWER(Category.STRING, SqlKind.OTHER_FUNCTION),
     TRIM(Category.STRING, SqlKind.TRIM),
+    SUBSTR(Category.STRING, SqlKind.OTHER_FUNCTION),
     SUBSTRING(Category.STRING, SqlKind.OTHER_FUNCTION),
     /**
      * String concatenation. Calcite's {@code SqlStdOperatorTable.CONCAT} is a
@@ -66,9 +67,23 @@ public enum ScalarFunction {
      * rename surfaces as a compile error rather than as a silent string mismatch at runtime.
      */
     CONCAT(Category.STRING, SqlKind.OTHER_FUNCTION, SqlStdOperatorTable.CONCAT),
+    CONCAT_WS(Category.STRING, SqlKind.OTHER_FUNCTION),
     CHAR_LENGTH(Category.STRING, SqlKind.OTHER_FUNCTION),
     REPLACE(Category.STRING, SqlKind.OTHER_FUNCTION),
     REGEXP_REPLACE(Category.STRING, SqlKind.OTHER_FUNCTION),
+    ASCII(Category.STRING, SqlKind.OTHER_FUNCTION),
+    LEFT(Category.STRING, SqlKind.OTHER_FUNCTION),
+    LENGTH(Category.STRING, SqlKind.OTHER_FUNCTION),
+    LOCATE(Category.STRING, SqlKind.OTHER_FUNCTION),
+    POSITION(Category.STRING, SqlKind.POSITION),
+    LTRIM(Category.STRING, SqlKind.OTHER_FUNCTION),
+    RTRIM(Category.STRING, SqlKind.OTHER_FUNCTION),
+    REVERSE(Category.STRING, SqlKind.OTHER_FUNCTION),
+    RIGHT(Category.STRING, SqlKind.OTHER_FUNCTION),
+    TOSTRING(Category.STRING, SqlKind.OTHER_FUNCTION),
+    NUMBER_TO_STRING(Category.STRING, SqlKind.OTHER_FUNCTION), // Alias for TOSTRING
+    TONUMBER(Category.STRING, SqlKind.OTHER_FUNCTION),
+    STRCMP(Category.STRING, SqlKind.OTHER_FUNCTION),
 
     // ── Math ─────────────────────────────────────────────────────────
     PLUS(Category.MATH, SqlKind.PLUS),

sandbox/plugins/analytics-backend-datafusion/rust/src/session_context.rs

@@ -111,6 +111,7 @@ pub async unsafe fn create_session_context(
         .build();
 
     let ctx = SessionContext::new_with_state(state);
+    crate::udf::register_all(&ctx);
 
     // Register default ListingTable for parquet scans
     let listing_options = ListingOptions::new(Arc::new(ParquetFormat::new()))

sandbox/plugins/analytics-backend-datafusion/rust/src/udf/mod.rs

@@ -113,10 +113,14 @@ pub(crate) fn coerce_args(
 }
 
 pub mod convert_tz;
+pub mod tonumber;
+pub mod tostring;
 
 pub fn register_all(ctx: &SessionContext) {
     convert_tz::register_all(ctx);
-    log::info!("OpenSearch UDF register_all: convert_tz registered");
+    tonumber::register_all(ctx);
+    tostring::register_all(ctx);
+    log::info!("OpenSearch UDF register_all: convert_tz, tonumber, tostring registered");
 }
 
 #[cfg(test)]