panbingkun commented on code in PR #47364:
URL: https://github.com/apache/spark/pull/47364#discussion_r1749707778


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sql/core/src/main/scala/org/apache/spark/sql/execution/command/ShowCollationsCommand.scala:
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@@ -0,0 +1,82 @@
+/*
+ * 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.command
+
+import org.apache.spark.sql.{Row, SparkSession}
+import org.apache.spark.sql.catalyst.analysis.ResolvedNamespace
+import org.apache.spark.sql.catalyst.expressions.{Attribute, 
AttributeReference}
+import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
+import org.apache.spark.sql.catalyst.util.CollationFactory.Collation
+import org.apache.spark.sql.types.StringType
+
+/**
+ * A command for `SHOW COLLATIONS`.
+ *
+ * The syntax of this command is:
+ * {{{
+ *    SHOW identifier? COLLATIONS ((FROM | IN) ns=identifierReference)? (LIKE? 
pattern=stringLit);
+ * }}}
+ */
+case class ShowCollationsCommand(
+    ns: LogicalPlan,
+    userScope: Boolean,
+    systemScope: Boolean,
+    pattern: Option[String]) extends UnaryRunnableCommand {
+
+  override val output: Seq[Attribute] = Seq(
+    AttributeReference("COLLATION_CATALOG", StringType, nullable = false)(),
+    AttributeReference("COLLATION_SCHEMA", StringType, nullable = false)(),
+    AttributeReference("COLLATION_NAME", StringType, nullable = false)(),
+    AttributeReference("LANGUAGE", StringType)(),
+    AttributeReference("COUNTRY", StringType)(),
+    AttributeReference("ACCENT_SENSITIVITY", StringType, nullable = false)(),
+    AttributeReference("CASE_SENSITIVITY", StringType, nullable = false)(),
+    AttributeReference("PAD_ATTRIBUTE", StringType, nullable = false)(),
+    AttributeReference("ICU_VERSION", StringType)())
+
+  override def run(sparkSession: SparkSession): Seq[Row] = {
+    val ResolvedNamespace(catalog, ns, _) = child
+
+    val systemCollations: Seq[Collation] = if (systemScope) {
+      sparkSession.sessionState.catalog.listCollations(pattern)
+    } else Seq.empty
+
+    val userCollations: Seq[Collation] = if (userScope) {

Review Comment:
   > This looks great. Could we maybe force UTF8_BINRAY and UTF8_LCASE to be 
the first ones? These are spark internal implementations and I would expect the 
default collation to appear first. What do you think?
   
   Okay, I completely agree, let me update it.



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