[SPARK-20303][SQL] Rename createTempFunction to registerFunction

### What changes were proposed in this pull request?
Session catalog API `createTempFunction` is being used by Hive build-in functions, persistent functions, and temporary functions. Thus, the name is confusing. This PR is to rename it by `registerFunction`. Also we can move construction of `FunctionBuilder` and `ExpressionInfo` into the new `registerFunction`, instead of duplicating the logics everywhere.

In the next PRs, the remaining Function-related APIs also need cleanups.

### How was this patch tested?
Existing test cases.

Author: Xiao Li <gatorsmile@gmail.com>

Closes #17615 from gatorsmile/cleanupCreateTempFunction.

2 files changed, 6 insertions, 8 deletions

diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/command/functions.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/command/functions.scala
index 5687f93324..e0d0029369 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/command/functions.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/command/functions.scala
@@ -51,6 +51,7 @@ case class CreateFunctionCommand(
 
   override def run(sparkSession: SparkSession): Seq[Row] = {
     val catalog = sparkSession.sessionState.catalog
+    val func = CatalogFunction(FunctionIdentifier(functionName, databaseName), className, resources)
     if (isTemp) {
       if (databaseName.isDefined) {
         throw new AnalysisException(s"Specifying a database in CREATE TEMPORARY FUNCTION " +
@@ -59,17 +60,13 @@ case class CreateFunctionCommand(
       // We first load resources and then put the builder in the function registry.
       // Please note that it is allowed to overwrite an existing temp function.
       catalog.loadFunctionResources(resources)
-      val info = new ExpressionInfo(className, functionName)
-      val builder = catalog.makeFunctionBuilder(functionName, className)
-      catalog.createTempFunction(functionName, info, builder, ignoreIfExists = false)
+      catalog.registerFunction(func, ignoreIfExists = false)
     } else {
       // For a permanent, we will store the metadata into underlying external catalog.
       // This function will be loaded into the FunctionRegistry when a query uses it.
       // We do not load it into FunctionRegistry right now.
       // TODO: should we also parse "IF NOT EXISTS"?
-      catalog.createFunction(
-        CatalogFunction(FunctionIdentifier(functionName, databaseName), className, resources),
-        ignoreIfExists = false)
+      catalog.createFunction(func, ignoreIfExists = false)
     }
     Seq.empty[Row]
   }
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/internal/CatalogSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/internal/CatalogSuite.scala
index 6469e501c1..8f9c52cb1e 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/internal/CatalogSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/internal/CatalogSuite.scala
@@ -75,9 +75,10 @@ class CatalogSuite
   }
 
   private def createTempFunction(name: String): Unit = {
-    val info = new ExpressionInfo("className", name)
     val tempFunc = (e: Seq[Expression]) => e.head
-    sessionCatalog.createTempFunction(name, info, tempFunc, ignoreIfExists = false)
+    val funcMeta = CatalogFunction(FunctionIdentifier(name, None), "className", Nil)
+    sessionCatalog.registerFunction(
+      funcMeta, ignoreIfExists = false, functionBuilder = Some(tempFunc))
   }
 
   private def dropFunction(name: String, db: Option[String] = None): Unit = {