make SimpleQueryResult a container for client warnings, and expose th…

…ose warnings via QueryResult

src/main/java/org/apache/cassandra/distributed/api/QueryResult.java

@@ -58,6 +58,8 @@
 public interface QueryResult extends Iterator<Row>
 {
     List<String> names();
+
+    List<String> warnings();
 
     default QueryResult filter(Predicate<Row> fn)
     {

src/main/java/org/apache/cassandra/distributed/api/QueryResults.java

@@ -80,7 +80,8 @@ public static Builder builder()
 
         private int numColumns = UNSET;
         private String[] names;
-        private List<Object[]> results = new ArrayList<>();
+        private final List<Object[]> results = new ArrayList<>();
+        private final List<String> warnings = new ArrayList<>();
 
         public Builder columns(String... columns)
         {
@@ -110,6 +111,12 @@ public Builder row(Object... values)
             return this;
         }
 
+        public Builder warning(String message)
+        {
+            warnings.add(message);
+            return this;
+        }
+
         public SimpleQueryResult build()
         {
             if (names == null)
@@ -120,7 +127,8 @@ public SimpleQueryResult build()
                 for (int i = 0; i < numColumns; i++)
                     names[i] = "unknown";
             }
-            return new SimpleQueryResult(names, results.stream().toArray(Object[][]::new));
+
+            return new SimpleQueryResult(names, results.toArray(new Object[0][]), warnings);
         }
     }
 
@@ -146,6 +154,12 @@ public List<String> names()
             return names;
         }
 
+        @Override
+        public List<String> warnings()
+        {
+            throw new UnsupportedOperationException("Warnings are not yet supported for " + getClass().getSimpleName());
+        }
+
         @Override
         public boolean hasNext()
         {
@@ -176,6 +190,12 @@ public List<String> names()
         {
             return delegate.names();
         }
+
+        @Override 
+        public List<String> warnings()
+        {
+            return delegate.warnings();
+        }
 
         @Override
         public boolean hasNext()

src/main/java/org/apache/cassandra/distributed/api/SimpleQueryResult.java

@@ -63,14 +63,21 @@ public class SimpleQueryResult implements QueryResult
 {
     private final String[] names;
     private final Object[][] results;
+    private final List<String> warnings;
     private final Predicate<Row> filter;
     private final Row row;
     private int offset = -1;
 
     public SimpleQueryResult(String[] names, Object[][] results)
+    {
+        this(names, results, Collections.emptyList());
+    }
+
+    public SimpleQueryResult(String[] names, Object[][] results, List<String> warnings)
     {
         this.names = Objects.requireNonNull(names, "names");
         this.results = results;
+        this.warnings = Objects.requireNonNull(warnings, "warnings");
         this.row = new Row(names);
         this.filter = ignore -> true;
     }
@@ -79,6 +86,7 @@ private SimpleQueryResult(String[] names, Object[][] results, Predicate<Row> fil
     {
         this.names = names;
         this.results = results;
+        this.warnings = Collections.emptyList();
         this.filter = filter;
         this.offset = offset;
         this.row = new Row(names);
@@ -89,6 +97,12 @@ public List<String> names()
         return Collections.unmodifiableList(Arrays.asList(names));
     }
 
+    @Override
+    public List<String> warnings()
+    {
+        return Collections.unmodifiableList(warnings);
+    }
+
     public SimpleQueryResult filter(Predicate<Row> fn)
     {
         return new SimpleQueryResult(names, results, filter.and(fn), offset);

src/test/java/org/apache/cassandra/distributed/api/QueryResultTest.java

@@ -23,9 +23,11 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.NoSuchElementException;
+import java.util.Objects;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
@@ -38,6 +40,7 @@ public void empty()
         QueryResult result = QueryResults.empty();
 
         assertThat(result.names()).isEmpty();
+        assertThat(result.warnings()).isEmpty();
         assertThat(result.toString()).isEqualTo("[]");
 
         assertThat(result.hasNext()).isFalse();
@@ -52,6 +55,43 @@ public void empty()
         assertThatThrownBy(it::next).isInstanceOf(NoSuchElementException.class);
     }
 
+    @Test
+    public void warnings()
+    {
+        String[] names = { "fname", "lname"};
+        Object[][] rows = { new Object[] { "david", "capwell"} };
+        SimpleQueryResult result = new SimpleQueryResult(names, rows, Collections.singletonList("test warning"));
+        assertThat(result.warnings()).isEqualTo(Collections.singletonList("test warning"));
+    }
+
+    @Test
+    public void delegatedWarnings()
+    {
+        String[] names = { "fname", "lname"};
+        Object[][] rows = { new Object[] { "david", "capwell"} };
+        SimpleQueryResult delegate = new SimpleQueryResult(names, rows, Collections.singletonList("test warning"));
+        QueryResult filteredResult = QueryResults.filter(delegate, Objects::nonNull);
+        assertThat(filteredResult.warnings()).isEqualTo(Collections.singletonList("test warning"));
+    }
+
+    @Test
+    public void warningsFromBuilder()
+    {
+        String[] names = { "fname", "lname"};
+        Object[][] rows = { new Object[] { "david", "capwell"} };
+        String warning = "test warning";
+        SimpleQueryResult expected = new SimpleQueryResult(names, rows, Collections.singletonList(warning));
+
+        SimpleQueryResult fromBuilder = QueryResults.builder()
+                                                    .columns(names)
+                                                    .row(rows[0])
+                                                    .warning(warning)
+                                                    .build();
+
+        assertThat(fromBuilder.warnings()).isEqualTo(Collections.singletonList(warning));
+        assertThat(fromBuilder.warnings()).isEqualTo(expected.warnings());
+    }
+
     @Test
     public void equals()
     {