Improve timeout error for background search

opensearch/src/main/java/org/opensearch/sql/opensearch/executor/OpenSearchExecutionEngine.java

@@ -36,6 +36,7 @@
 import org.apache.calcite.sql.validate.SqlUserDefinedFunction;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.opensearch.OpenSearchTimeoutException;
 import org.opensearch.sql.ast.statement.Explain.ExplainFormat;
 import org.opensearch.sql.calcite.CalcitePlanContext;
 import org.opensearch.sql.calcite.utils.CalciteToolsHelper.OpenSearchRelRunners;
@@ -215,6 +216,11 @@ public void execute(
                         buildResultSet(
                             result, rel.getRowType(), context.sysLimit.querySizeLimit(), listener);
                       } catch (SQLException e) {
+                        if (e.getCause() instanceof OpenSearchTimeoutException) {
+                          // Special case: execution failed due to timing, not other generic runtime
+                          // issues
+                          throw (OpenSearchTimeoutException) e.getCause();
+                        }
                         throw new RuntimeException(e);
                       }
                       return null;

opensearch/src/main/java/org/opensearch/sql/opensearch/storage/scan/BackgroundSearchScanner.java

@@ -13,6 +13,7 @@
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
 import javax.annotation.Nullable;
+import org.opensearch.OpenSearchTimeoutException;
 import org.opensearch.sql.data.model.ExprValue;
 import org.opensearch.sql.exception.NonFallbackCalciteException;
 import org.opensearch.sql.opensearch.client.OpenSearchClient;
@@ -104,11 +105,16 @@ private OpenSearchResponse getCurrentResponse(OpenSearchRequest request) {
     if (isAsync()) {
       try {
         return nextBatchFuture.get();
-      } catch (InterruptedException | ExecutionException e) {
+      } catch (ExecutionException e) {
         throw new NonFallbackCalciteException(
             "Failed to fetch data from the index: the background task failed or interrupted.\n"
                 + "  Inner error: "
                 + e.getMessage());
+      } catch (InterruptedException e) {
+        throw new OpenSearchTimeoutException(
+            new InterruptedException(
+                "Execution of the index search timed out. Increase the timeout via the"
+                    + " `ppl.query.timeout` setting."));
       }
     } else {
       return client.search(request);