From 55c49fdc154f84cd314972c4cc6fd7c272627a83 Mon Sep 17 00:00:00 2001
From: Pratham Desai <prathamd94@gmail.com>
Date: Sat, 11 Mar 2023 20:51:00 -0500
Subject: [PATCH] Avoid deserialization when no columns are needed

This improves performance for count(const) or count(*) queris
on formats that use GenericHiveRecordCursor.
---
 .../io/trino/plugin/hive/GenericHiveRecordCursor.java | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/plugin/trino-hive/src/main/java/io/trino/plugin/hive/GenericHiveRecordCursor.java b/plugin/trino-hive/src/main/java/io/trino/plugin/hive/GenericHiveRecordCursor.java
index 8ac0b6a7cb22..e67c25cd8136 100644
--- a/plugin/trino-hive/src/main/java/io/trino/plugin/hive/GenericHiveRecordCursor.java
+++ b/plugin/trino-hive/src/main/java/io/trino/plugin/hive/GenericHiveRecordCursor.java
@@ -217,11 +217,14 @@ public boolean advanceNextPosition()
                 return false;
             }
 
-            // reset loaded flags
-            Arrays.fill(loaded, false);
+            // Only deserialize the value if atleast one column is required
+            if (types.length > 0) {
+                // reset loaded flags
+                Arrays.fill(loaded, false);
 
-            // decode value
-            rowData = deserializer.deserialize(value);
+                // decode value
+                rowData = deserializer.deserialize(value);
+            }
 
             return true;
         }