[GitHub] [cassandra] alex-ninja commented on a change in pull request #1117: CASSANDRA-16806. Allow TRUNCATE to work on Virtual Tables if the implementation allows it.

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

alex-ninja commented on a change in pull request #1117:
URL: https://github.com/apache/cassandra/pull/1117#discussion_r675874045



##########
File path: test/unit/org/apache/cassandra/cql3/validation/entities/VirtualTableTest.java
##########
@@ -317,6 +365,32 @@ public void testModifications() throws Throwable
                              "INSERT INTO test_virtual_ks.vt2 (key, value) VALUES ('pk2', 22) IF NOT EXISTS");
     }
 
+    @Test
+    public void testTruncationOnTruncatableTable() throws Throwable
+    {
+        // check for existing records
+        assertRows(execute("SELECT * FROM test_virtual_ks.vt4"),
+                row("pk1", 1),
+                row("pk2", 2));
+
+        // truncate
+        execute("TRUNCATE test_virtual_ks.vt4");
+
+        // check that truncation is applied
+        assertEmpty(execute("SELECT * FROM test_virtual_ks.vt4"));
+    }
+
+    @Test
+    public void testInvalidDMLOperations() throws Throwable

Review comment:
       I moved truncation test from `testInvalidDDLOperations` to `testInvalidDMLOperations` because `TRUNCATE` is a DML operation. Also I added a test for `INSERT` into read-only VT - it was missing.

##########
File path: doc/source/new/virtualtables.rst
##########
@@ -42,11 +42,12 @@ Virtual tables and virtual keyspaces are quite different from regular tables and
 - Virtual tables are not replicated
 - Virtual tables are local only and non distributed
 - Virtual tables have no associated SSTables
+- Virtual tables support ``TRUNCATE`` only if the underlaying implementation allows it
 - Consistency level of the queries sent virtual tables are ignored
-- Virtual tables are managed by Cassandra and a user cannot run  DDL to create new virtual tables or DML to modify existing virtual       tables

Review comment:
       ``TRUNCATE`` is a DML

##########
File path: test/unit/org/apache/cassandra/cql3/validation/entities/VirtualTableTest.java
##########
@@ -317,6 +365,32 @@ public void testModifications() throws Throwable
                              "INSERT INTO test_virtual_ks.vt2 (key, value) VALUES ('pk2', 22) IF NOT EXISTS");
     }
 
+    @Test
+    public void testTruncationOnTruncatableTable() throws Throwable

Review comment:
       This is a unit test to cover the actual change.

##########
File path: test/unit/org/apache/cassandra/cql3/validation/entities/VirtualTableTest.java
##########
@@ -118,16 +147,15 @@ public DataSet data()
         };
         VirtualTable vt2 = new WritableVirtualTable(KS_NAME, VT2_NAME);
 
-        TableMetadata vt3Metadata =
-        TableMetadata.builder(KS_NAME, VT3_NAME)

Review comment:
       It was badly formatted.

##########
File path: test/unit/org/apache/cassandra/cql3/validation/entities/VirtualTableTest.java
##########
@@ -88,17 +89,45 @@ public void apply(PartitionUpdate update)
         }
     }
 
+    private abstract static class TruncatableVirtualTable extends AbstractVirtualTable
+    {
+        private boolean isTruncated = false;
+
+        TruncatableVirtualTable(TableMetadata metadata)
+        {
+            super(metadata);
+        }
+
+        @Override
+        public DataSet data()
+        {
+            if (isTruncated)

Review comment:
       Just a simple way to emulate truncation. Theoretically I could use a collection, smth like that:
   ```
   TruncatableVirtualTable(TableMetadata metadata, Map<String, Integer> refToCleanupData) 
   
   public void truncate()
   {
           refToCleanupData.clear();
   }
   ```
   ```
   Map<String, Integer> truncatableData = <some data>;
   VirtualTable vt4 = new TruncatableVirtualTable(vt4Metadata, truncatableData)
   {
   
       public DataSet data()
       {
               SimpleDataSet data = new SimpleDataSet(metadata());
               truncatableData.forEach((key, value) -> data.row(key).column("value", value));
               return data;
       }
   
   }
   ```
   
   This way looks more similar to a real use case. Please, let me know if this one is more preferable for a unit test.

##########
File path: test/unit/org/apache/cassandra/cql3/validation/entities/VirtualTableTest.java
##########
@@ -88,17 +89,45 @@ public void apply(PartitionUpdate update)
         }
     }
 
+    private abstract static class TruncatableVirtualTable extends AbstractVirtualTable
+    {
+        private boolean isTruncated = false;
+
+        TruncatableVirtualTable(TableMetadata metadata)
+        {
+            super(metadata);
+        }
+
+        @Override
+        public DataSet data()
+        {
+            if (isTruncated)
+            {
+                return new SimpleDataSet(metadata());
+            }
+
+            return truncatableData();
+        }
+
+        abstract protected DataSet truncatableData();
+
+        @Override
+        public void truncate()
+        {
+            isTruncated = true;
+        }
+    }
+
     @BeforeClass
     public static void setUpClass()
     {
-        TableMetadata vt1Metadata =
-        TableMetadata.builder(KS_NAME, VT1_NAME)

Review comment:
       It was badly formatted.




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