[SPARK-49078][SQL] Support show columns syntax in v2 table

### What changes were proposed in this pull request?

Support v2 table with show columns syntax.

### Why are the changes needed?

In lakehouse format such as Paimon、Iceberg，table are v2 which not support show column syntax，this pr is aimed to support it

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

DataSourceV2SQLSuite

### Was this patch authored or co-authored using generative AI tooling?

no

Closes apache#47568 from xuzifu666/support_show_columns_v2.

Lead-authored-by: xuyu <11161569@vivo.com>
Co-authored-by: Kent Yao <yao@apache.org>
Signed-off-by: Kent Yao <yao@apache.org>

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/DataSourceV2Strategy.scala

@@ -473,8 +473,8 @@ class DataSourceV2Strategy(session: SparkSession) extends Strategy with Predicat
         Seq(part).asResolvedPartitionSpecs.head,
         recacheTable(r)) :: Nil
 
-    case ShowColumns(_: ResolvedTable, _, _) =>
-      throw QueryCompilationErrors.showColumnsNotSupportedForV2TablesError()
+    case ShowColumns(resolvedTable: ResolvedTable, _, output) =>
+      ShowColumnsExec(output, resolvedTable) :: Nil
 
     case r @ ShowPartitions(
         ResolvedTable(catalog, _, table: SupportsPartitionManagement, _),

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/ShowColumnsTableExec.scala

@@ -0,0 +1,34 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.execution.datasources.v2
+
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.analysis.ResolvedTable
+import org.apache.spark.sql.catalyst.expressions.Attribute
+import org.apache.spark.sql.execution.LeafExecNode
+
+/**
+ * Physical plan node for show columns from table.
+ */
+case class ShowColumnsExec(
+     output: Seq[Attribute],
+     resolvedTable: ResolvedTable) extends V2CommandExec with LeafExecNode {
+  override protected def run(): Seq[InternalRow] = {
+    resolvedTable.table.columns().map(f => toCatalystRow(f.name())).toSeq
+  }
+}

sql/core/src/test/scala/org/apache/spark/sql/connector/DataSourceV2SQLSuite.scala

@@ -2377,10 +2377,7 @@ class DataSourceV2SQLSuiteV1Filter
     val t = "testcat.ns1.ns2.tbl"
     withTable(t) {
       spark.sql(s"CREATE TABLE $t (id bigint, data string) USING foo")
-
-      testNotSupportedV2Command("SHOW COLUMNS", s"FROM $t")
-      testNotSupportedV2Command("SHOW COLUMNS", s"IN $t")
-      testNotSupportedV2Command("SHOW COLUMNS", "FROM tbl IN testcat.ns1.ns2")
+      checkAnswer(sql(s"SHOW COLUMNS FROM $t"), Seq(Row("id"), Row("data")))
     }
   }
 
@@ -2497,7 +2494,6 @@ class DataSourceV2SQLSuiteV1Filter
         verify(s"CACHE TABLE $t")
         verify(s"UNCACHE TABLE $t")
         verify(s"TRUNCATE TABLE $t")
-        verify(s"SHOW COLUMNS FROM $t")
       }
     }