From b73bf8802a32f0b731b21c752d7f96a57ee4770a Mon Sep 17 00:00:00 2001
From: Cheng Pan <chengpan@apache.org>
Date: Mon, 25 Mar 2024 18:34:40 +0800
Subject: [PATCH] [KYUUBI #6205] Backport SPARK-47300: quoteIfNeeded should
 quote identifier starts with digits
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# :mag: Description

The function is forked from Apache Spark, and we should align behavior with upstream timely.

## Types of changes :bookmark:

- [x] Bugfix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to change)

## Test Plan 🧪

Pass GA.

---

# Checklist 📝

- [x] This patch was not authored or co-authored using [Generative Tooling](https://www.apache.org/legal/generative-tooling.html)

**Be nice. Be informative.**

Closes #6205 from pan3793/quoteIfNeeded.

Closes #6205

2e44fe757 [Cheng Pan] Backport SPARK-47300: quoteIfNeeded should quote identifier starts with digits

Authored-by: Cheng Pan <chengpan@apache.org>
Signed-off-by: Cheng Pan <chengpan@apache.org>
---
 .../engine/spark/util/SparkCatalogUtils.scala  | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/externals/kyuubi-spark-sql-engine/src/main/scala/org/apache/kyuubi/engine/spark/util/SparkCatalogUtils.scala b/externals/kyuubi-spark-sql-engine/src/main/scala/org/apache/kyuubi/engine/spark/util/SparkCatalogUtils.scala
index b55319830b5..ff4564e5462 100644
--- a/externals/kyuubi-spark-sql-engine/src/main/scala/org/apache/kyuubi/engine/spark/util/SparkCatalogUtils.scala
+++ b/externals/kyuubi-spark-sql-engine/src/main/scala/org/apache/kyuubi/engine/spark/util/SparkCatalogUtils.scala
@@ -377,14 +377,22 @@ object SparkCatalogUtils extends Logging {
     // format: on
   }
 
-  /**
-   * Forked from Apache Spark's [[org.apache.spark.sql.catalyst.util.quoteIfNeeded]]
-   */
+  // SPARK-47300 (4.0.0): quoteIfNeeded should quote identifier starts with digits
+  private val validIdentPattern = Pattern.compile("^[a-zA-Z_][a-zA-Z0-9_]*")
+
+  // Forked from Apache Spark's [[org.apache.spark.sql.catalyst.util.QuotingUtils.quoteIfNeeded]]
   def quoteIfNeeded(part: String): String = {
-    if (part.matches("[a-zA-Z0-9_]+") && !part.matches("\\d+")) {
+    if (validIdentPattern.matcher(part).matches()) {
       part
     } else {
-      s"`${part.replace("`", "``")}`"
+      quoteIdentifier(part)
     }
   }
+
+  // Forked from Apache Spark's [[org.apache.spark.sql.catalyst.util.QuotingUtils.quoteIdentifier]]
+  def quoteIdentifier(name: String): String = {
+    // Escapes back-ticks within the identifier name with double-back-ticks, and then quote the
+    // identifier with back-ticks.
+    "`" + name.replace("`", "``") + "`"
+  }
 }