From b524a991363c707bf5bf6705c8e661fc4166e2d2 Mon Sep 17 00:00:00 2001
From: Deepa-George <deepa.george@ibm.com>
Date: Wed, 13 Nov 2024 14:59:56 +0530
Subject: [PATCH] Add support for ALTER VIEW [ IF EXISTS ] RENAME TO statement
 in Memory connector

---
 .../src/main/sphinx/connector/memory.rst      |  9 ++++++++
 .../presto/plugin/memory/MemoryMetadata.java  | 15 +++++++++++++
 .../plugin/memory/TestMemoryMetadata.java     | 10 ++++++++-
 .../presto/plugin/memory/TestMemorySmoke.java | 22 +++++++++++++++++++
 4 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/presto-docs/src/main/sphinx/connector/memory.rst b/presto-docs/src/main/sphinx/connector/memory.rst
index 0a49cc4a6290..041282c60d84 100644
--- a/presto-docs/src/main/sphinx/connector/memory.rst
+++ b/presto-docs/src/main/sphinx/connector/memory.rst
@@ -92,6 +92,15 @@ To delete an existing table:
 
 .. note:: After using ``DROP TABLE``, memory is not released immediately. It is released after the next write access to the memory connector.
 
+ALTER VIEW
+^^^^^^^^^^
+
+Alter view operations to alter the name of an existing view to a new name is supported in the Memory connector.
+
+.. code-block:: sql
+
+    ALTER VIEW memory.default.nation RENAME TO memory.default.new_nation;
+
 Memory Connector Limitations
 ----------------------------
 
diff --git a/presto-memory/src/main/java/com/facebook/presto/plugin/memory/MemoryMetadata.java b/presto-memory/src/main/java/com/facebook/presto/plugin/memory/MemoryMetadata.java
index 0c8c9e8b62f9..b600eabc8ea1 100644
--- a/presto-memory/src/main/java/com/facebook/presto/plugin/memory/MemoryMetadata.java
+++ b/presto-memory/src/main/java/com/facebook/presto/plugin/memory/MemoryMetadata.java
@@ -291,6 +291,21 @@ else if (views.putIfAbsent(viewName, viewData) != null) {
         }
     }
 
+    @Override
+    public synchronized void renameView(ConnectorSession session, SchemaTableName viewName, SchemaTableName newViewName)
+    {
+        checkSchemaExists(newViewName.getSchemaName());
+        if (tableIds.containsKey(newViewName)) {
+            throw new PrestoException(ALREADY_EXISTS, "Table already exists: " + newViewName);
+        }
+
+        if (views.containsKey(newViewName)) {
+            throw new PrestoException(ALREADY_EXISTS, "View already exists: " + newViewName);
+        }
+
+        views.put(newViewName, views.remove(viewName));
+    }
+
     @Override
     public synchronized void dropView(ConnectorSession session, SchemaTableName viewName)
     {
diff --git a/presto-memory/src/test/java/com/facebook/presto/plugin/memory/TestMemoryMetadata.java b/presto-memory/src/test/java/com/facebook/presto/plugin/memory/TestMemoryMetadata.java
index 1a1c200935f2..acc108c57a76 100644
--- a/presto-memory/src/test/java/com/facebook/presto/plugin/memory/TestMemoryMetadata.java
+++ b/presto-memory/src/test/java/com/facebook/presto/plugin/memory/TestMemoryMetadata.java
@@ -226,6 +226,8 @@ public void testViews()
                 test2,
                 ImmutableList.of(new ColumnMetadata("a", BIGINT)));
 
+        SchemaTableName test3 = new SchemaTableName("test", "test_view3");
+
         // create schema
         metadata.createSchema(SESSION, "test", ImmutableMap.of());
 
@@ -265,8 +267,14 @@ public void testViews()
         views = metadata.getViews(SESSION, new SchemaTablePrefix("test"));
         assertEquals(views.keySet(), ImmutableSet.of(test2));
 
+        // rename second view
+        metadata.renameView(SESSION, test2, test3);
+
+        Map<?, ?> result = metadata.getViews(SESSION, new SchemaTablePrefix("test"));
+        assertTrue(result.containsKey(test3));
+
         // drop second view
-        metadata.dropView(SESSION, test2);
+        metadata.dropView(SESSION, test3);
 
         views = metadata.getViews(SESSION, new SchemaTablePrefix("test"));
         assertTrue(views.isEmpty());
diff --git a/presto-memory/src/test/java/com/facebook/presto/plugin/memory/TestMemorySmoke.java b/presto-memory/src/test/java/com/facebook/presto/plugin/memory/TestMemorySmoke.java
index 35c31c556540..4e0a43685291 100644
--- a/presto-memory/src/test/java/com/facebook/presto/plugin/memory/TestMemorySmoke.java
+++ b/presto-memory/src/test/java/com/facebook/presto/plugin/memory/TestMemorySmoke.java
@@ -185,6 +185,28 @@ public void testViews()
         assertQueryFails("DROP VIEW test_view", "line 1:1: View 'memory.default.test_view' does not exist");
     }
 
+    @Test
+    public void testRenameView()
+    {
+        @Language("SQL") String query = "SELECT orderkey, orderstatus, totalprice / 2 half FROM orders";
+
+        assertUpdate("CREATE VIEW test_view_to_be_renamed AS " + query);
+        assertUpdate("ALTER VIEW test_view_to_be_renamed RENAME TO test_view_renamed");
+        assertQuery("SELECT * FROM test_view_renamed", query);
+
+        assertUpdate("CREATE SCHEMA test_different_schema");
+        assertQueryFails("ALTER VIEW test_view_renamed RENAME TO test_different_schema.test_view_renamed", "line 1:1: View rename across schemas is not supported");
+        assertUpdate("DROP VIEW test_view_renamed");
+        assertUpdate("DROP SCHEMA test_different_schema");
+    }
+
+    @Test
+    public void testRenameViewIfNotExists()
+    {
+        assertQueryFails("ALTER VIEW test_rename_view_not_exist RENAME TO test_renamed_view_not_exist", "line 1:1: View 'memory.default.test_rename_view_not_exist' does not exist");
+        assertQuerySucceeds("ALTER VIEW IF EXISTS test_rename_view_not_exist RENAME TO test_renamed_view_not_exist");
+    }
+
     private List<QualifiedObjectName> listMemoryTables()
     {
         return getQueryRunner().listTables(getSession(), "memory", "default");