[GitHub] [spark] cloud-fan commented on a change in pull request #28840: [SPARK-31999][SQL] Add REFRESH FUNCTION command

[GitBox <gi...@apache.org>]

cloud-fan commented on a change in pull request #28840:
URL: https://github.com/apache/spark/pull/28840#discussion_r453643288



##########
File path: docs/sql-ref-syntax-aux-cache-refresh-function.md
##########
@@ -0,0 +1,60 @@
+---
+layout: global
+title: REFRESH FUNCTION
+displayTitle: REFRESH FUNCTION
+license: |
+  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.
+---
+
+### Description
+
+`REFRESH FUNCTION` statement invalidates the cached function entry, which includes a class name
+and resource location of the given function. The invalidated cache is populated right away.
+Note that `REFRESH FUNCTION` only works for permanent functions. Refreshing native functions or temporary functions will cause an exception.
+
+### Syntax
+
+```sql
+REFRESH FUNCTION function_identifier
+```
+
+### Parameters
+
+* **function_identifier**
+
+    Specifies a function name, which is either a qualified or unqualified name. If no database identifier is provided, uses the current database.
+
+    **Syntax:** `[ database_name. ] function_name`
+
+### Examples
+
+```sql
+-- The cached entry of the function will be refreshed
+-- The function is resolved from the current database as the function name is unqualified.
+REFRESH FUNCTION func1;
+
+-- The cached entry of the function will be refreshed
+-- The function is resolved from tempDB database as the function name is qualified.
+REFRESH FUNCTION tempDB.func1;   

Review comment:
       nit: `db1.func1`? `tempDB` sounds like Spark supports temporary database, while it doesn't.

##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/connector/catalog/LookupCatalog.scala
##########
@@ -155,4 +155,31 @@ private[sql] trait LookupCatalog extends Logging {
         None
     }
   }
+
+  // TODO: move function related v2 statements to the new framework.

Review comment:
       @imback82 do you have time to work on this TODO?

##########
File path: sql/core/src/main/scala/org/apache/spark/sql/execution/command/functions.scala
##########
@@ -236,6 +236,45 @@ case class ShowFunctionsCommand(
   }
 }
 
+
+/**
+ * A command for users to refresh the persistent function.
+ * The syntax of using this command in SQL is:
+ * {{{
+ *    REFRESH FUNCTION functionName
+ * }}}
+ */
+case class RefreshFunctionCommand(
+    databaseName: Option[String],
+    functionName: String)
+  extends RunnableCommand {
+
+  override def run(sparkSession: SparkSession): Seq[Row] = {
+    val catalog = sparkSession.sessionState.catalog
+    if (FunctionRegistry.builtin.functionExists(FunctionIdentifier(functionName))) {
+      throw new AnalysisException(s"Cannot refresh builtin function $functionName")
+    }
+    if (catalog.isTemporaryFunction(FunctionIdentifier(functionName, databaseName))) {
+      throw new AnalysisException(s"Cannot refresh temporary function $functionName")
+    }
+
+    val identifier = FunctionIdentifier(
+      functionName, Some(databaseName.getOrElse(catalog.getCurrentDatabase)))
+    // we only refresh the permanent function.
+    // 1. clear cached function.
+    // 2. register function if exists.
+    catalog.unregisterFunction(identifier, true)
+    if (catalog.isPersistentFunction(identifier)) {
+      val func = catalog.getFunctionMetadata(identifier)
+      catalog.registerFunction(func, true)

Review comment:
       Does `registerFunction` overwrite existing entry? If it does then we don't need to add `unregisterFunction` API.

##########
File path: sql/core/src/main/scala/org/apache/spark/sql/execution/command/functions.scala
##########
@@ -236,6 +236,45 @@ case class ShowFunctionsCommand(
   }
 }
 
+
+/**
+ * A command for users to refresh the persistent function.
+ * The syntax of using this command in SQL is:
+ * {{{
+ *    REFRESH FUNCTION functionName
+ * }}}
+ */
+case class RefreshFunctionCommand(
+    databaseName: Option[String],
+    functionName: String)
+  extends RunnableCommand {
+
+  override def run(sparkSession: SparkSession): Seq[Row] = {
+    val catalog = sparkSession.sessionState.catalog
+    if (FunctionRegistry.builtin.functionExists(FunctionIdentifier(functionName))) {
+      throw new AnalysisException(s"Cannot refresh builtin function $functionName")
+    }
+    if (catalog.isTemporaryFunction(FunctionIdentifier(functionName, databaseName))) {
+      throw new AnalysisException(s"Cannot refresh temporary function $functionName")
+    }
+
+    val identifier = FunctionIdentifier(
+      functionName, Some(databaseName.getOrElse(catalog.getCurrentDatabase)))
+    // we only refresh the permanent function.
+    // 1. clear cached function.
+    // 2. register function if exists.
+    catalog.unregisterFunction(identifier, true)

Review comment:
       shall we move this into the `if (catalog.isPersistentFunction(identifier))` branch?




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