Adjust comment: add rationale for writing to summary field source.

1 files changed, 6 insertions, 1 deletions

diff --git a/config-model/src/main/java/com/yahoo/schema/processing/IndexingOutputs.java b/config-model/src/main/java/com/yahoo/schema/processing/IndexingOutputs.java
index 385e030130b..071c2878ae8 100644
--- a/config-model/src/main/java/com/yahoo/schema/processing/IndexingOutputs.java
+++ b/config-model/src/main/java/com/yahoo/schema/processing/IndexingOutputs.java
@@ -137,7 +137,12 @@ public class IndexingOutputs extends Processor {
                 for (String fieldName : summaryFields) {
                     ret.add(new SummaryExpression(fieldName));
                 }
-                // Write to summary field source
+                /*
+                 * Write to summary field source. AddExtraFieldsToDocument processor adds the "copy"
+                 * summary transform to summary fields without a corresponding explicitly declared
+                 * document field (2023-11-01). Future vespa versions will stop adding document
+                 * fields for those summary fields.
+                 */
                 if (!summaryFields.contains(field.getName())) {
                     ret.add(new SummaryExpression(field.getName()));
                 }