don't inject +score unless coordinator requests it; this is a cleaner…

… approach than ignoring it when serialization fails later

src/java/org/apache/cassandra/cql3/statements/SelectStatement.java

@@ -103,9 +103,8 @@ public class SelectStatement implements CQLStatement.SingleKeyspaceCqlStatement
 {
     // TODO remove this when we no longer need to downgrade to replicas that don't know about synthetic columns,
     // and the related code in
-    //  - Columns.Serializer.encodeBitmap
-    //  - UnfilteredSerializer.serializeRowBody)
     //  - StatementRestrictions.addOrderingRestrictions
+    //  - StorageAttachedIndexSearcher.PrimaryKeyIterator constructor
     public static final boolean ANN_USE_SYNTHETIC_SCORE = Boolean.parseBoolean(System.getProperty("cassandra.sai.ann_use_synthetic_score", "false"));
 
     private static final Logger logger = LoggerFactory.getLogger(SelectStatement.class);

src/java/org/apache/cassandra/db/Columns.java

@@ -716,15 +716,7 @@ private static long encodeBitmap(Collection<ColumnMetadata> columns, Columns sup
             for (ColumnMetadata column : columns)
             {
                 if (iter.next(column) == null)
-                {
-                    // We can't know for sure whether to add the synthetic score column because WildcardColumnFilter
-                    // just says "yes" to everything; instead, we just skip it here.
-                    // TODO remove this with SelectStatement.ANN_USE_SYNTHETIC_SCORE.
-                    if (column.isSynthetic())
-                        continue;
-
                     throw new IllegalStateException(columns + " is not a subset of " + superset);
-                }
 
                 int currentIndex = iter.indexOfCurrent();
                 int count = currentIndex - expectIndex;

src/java/org/apache/cassandra/db/filter/ColumnFilter.java

@@ -75,6 +75,9 @@ public abstract class ColumnFilter
 
     public static final Serializer serializer = new Serializer();
 
+    // TODO remove this with ANN_USE_SYNTHETIC_SCORE
+    public abstract boolean fetchesExplicitly(ColumnMetadata column);
+
     /**
      * The fetching strategy for the different queries.
      */
@@ -669,6 +672,12 @@ public boolean fetches(ColumnMetadata column)
             return true;
         }
 
+        @Override
+        public boolean fetchesExplicitly(ColumnMetadata column)
+        {
+            return false;
+        }
+
         @Override
         public boolean fetchedColumnIsQueried(ColumnMetadata column)
         {
@@ -817,6 +826,12 @@ public boolean fetches(ColumnMetadata column)
             return fetchingStrategy.fetchesAllColumns(column.isStatic()) || fetched.contains(column);
         }
 
+        @Override
+        public boolean fetchesExplicitly(ColumnMetadata column)
+        {
+            return fetched.contains(column);
+        }
+
         /**
          * Whether the provided complex cell (identified by its column and path), which is assumed to be _fetched_ by
          * this filter, is also _queried_ by the user.

src/java/org/apache/cassandra/db/rows/UnfilteredSerializer.java

@@ -242,11 +242,6 @@ private void serializeRowBody(Row row, int flags, SerializationHelper helper, Da
                 // with. So we use the ColumnMetadata from the "header" which is "current". Also see #11810 for what
                 // happens if we don't do that.
                 ColumnMetadata column = si.next(cd.column());
-                // We can't know for sure whether to add the synthetic score column because WildcardColumnFilter
-                // just says "yes" to everything; instead, we just skip it here.
-                // TODO remove this with SelectStatement.ANN_USE_SYNTHETIC_SCORE.
-                if (column == null)
-                    return;
                 assert column != null : cd.column.toString();
 
                 try

src/java/org/apache/cassandra/index/sai/plan/QueryController.java

@@ -195,6 +195,11 @@ public TableMetadata metadata()
         return command.metadata();
     }
 
+    public ReadCommand command()
+    {
+        return command;
+    }
+
     RowFilter.FilterElement filterOperation()
     {
         // NOTE: we cannot remove the order by filter expression here yet because it is used in the FilterTree class

src/java/org/apache/cassandra/index/sai/plan/StorageAttachedIndexSearcher.java

@@ -42,6 +42,7 @@
 import org.apache.cassandra.db.PartitionPosition;
 import org.apache.cassandra.db.ReadCommand;
 import org.apache.cassandra.db.ReadExecutionController;
+import org.apache.cassandra.db.filter.ColumnFilter;
 import org.apache.cassandra.db.marshal.FloatType;
 import org.apache.cassandra.db.partitions.UnfilteredPartitionIterator;
 import org.apache.cassandra.db.rows.AbstractUnfilteredRowIterator;
@@ -636,7 +637,7 @@ public UnfilteredRowIterator readAndValidatePartition(PrimaryKey pk, List<Primar
                         }
                     }
                 }
-                return isRowValid ? new PrimaryKeyIterator(partition, staticRow, row, sourceKeys) : null;
+                return isRowValid ? new PrimaryKeyIterator(partition, staticRow, row, sourceKeys, controller.command()) : null;
             }
         }
 
@@ -657,7 +658,7 @@ public static class PrimaryKeyIterator extends AbstractUnfilteredRowIterator
             private boolean consumed = false;
             private final Unfiltered row;
 
-            public PrimaryKeyIterator(UnfilteredRowIterator partition, Row staticRow, Unfiltered content, List<PrimaryKeyWithSortKey> primaryKeysWithScore)
+            public PrimaryKeyIterator(UnfilteredRowIterator partition, Row staticRow, Unfiltered content, List<PrimaryKeyWithSortKey> primaryKeysWithScore, ReadCommand command)
             {
                 super(partition.metadata(),
                       partition.partitionKey(),
@@ -668,7 +669,24 @@ public PrimaryKeyIterator(UnfilteredRowIterator partition, Row staticRow, Unfilt
                       partition.stats());
 
                 assert !primaryKeysWithScore.isEmpty();
-                if (!content.isRow() || !(primaryKeysWithScore.get(0) instanceof PrimaryKeyWithScore))
+                var isScoredRow = primaryKeysWithScore.get(0) instanceof PrimaryKeyWithScore;
+                if (!content.isRow() || !isScoredRow)
+                {
+                    this.row = content;
+                    return;
+                }
+
+                // When +score is added on the coordinator side, it's represented as a PrecomputedColumnFilter
+                // even in a 'SELECT *' because WCF is not capable of representing synthetic columns.
+                // This can be simplified when we remove ANN_USE_SYNTHETIC_SCORE
+                var tm = metadata();
+                var scoreColumn = ColumnMetadata.syntheticColumn(tm.keyspace,
+                                                                 tm.name,
+                                                                 ColumnMetadata.SYNTHETIC_SCORE_ID,
+                                                                 FloatType.instance);
+                var isScoreFetched = !(command.columnFilter() instanceof ColumnFilter.WildCardColumnFilter)
+                                     && command.columnFilter().fetchesExplicitly(scoreColumn);
+                if (!isScoreFetched)
                 {
                     this.row = content;
                     return;
@@ -680,11 +698,6 @@ public PrimaryKeyIterator(UnfilteredRowIterator partition, Row staticRow, Unfilt
                 columnData.addAll(originalRow.columnData());
 
                 // inject +score as a new column
-                var tm = metadata();
-                var scoreColumn = ColumnMetadata.syntheticColumn(tm.keyspace,
-                                                                 tm.name,
-                                                                 ColumnMetadata.SYNTHETIC_SCORE_ID,
-                                                                 FloatType.instance);
                 var pkWithScore = (PrimaryKeyWithScore) primaryKeysWithScore.get(0);
                 columnData.add(BufferCell.live(scoreColumn,
                                                FBUtilities.nowInSeconds(),

src/java/org/apache/cassandra/index/sai/plan/TopKProcessor.java

@@ -364,7 +364,7 @@ private float getScoreForRow(DecoratedKey key, Row row)
             return FloatType.instance.compose(cell.buffer());
         }
 
-        // TODO remove this once we enable the scored path for vector queries
+        // TODO remove this once we enable ANN_USE_SYNTHETIC_SCORE
         ByteBuffer value = indexContext.getValueOf(key, row, FBUtilities.nowInSeconds());
         if (value != null)
         {