From fe38f899cef8abfdcef636807fff0c62339ecd3e Mon Sep 17 00:00:00 2001
From: William Chong <william-chong@outlook.com>
Date: Tue, 5 May 2026 12:26:02 +0400
Subject: [PATCH 1/2] feat: add engineVersion option to projection create

Exposes the V2 projection engine introduced in KurrentDB. Setting
engineVersion(2) on CreateProjectionOptions selects V2; 0 (default)
or 1 selects V1. The option is pinned at create time and cannot be
changed via update.
---
 .../io/kurrent/dbclient/CreateProjection.java  |  3 +++
 .../dbclient/CreateProjectionOptions.java      | 18 ++++++++++++++++++
 .../protocol/v1/projectionmanagement.proto     |  1 +
 3 files changed, 22 insertions(+)

diff --git a/src/main/java/io/kurrent/dbclient/CreateProjection.java b/src/main/java/io/kurrent/dbclient/CreateProjection.java
index 480927b6..dd1b2b89 100644
--- a/src/main/java/io/kurrent/dbclient/CreateProjection.java
+++ b/src/main/java/io/kurrent/dbclient/CreateProjection.java
@@ -12,6 +12,7 @@ class CreateProjection {
     private final String query;
     private final boolean trackEmittedStreams;
     private final boolean emitEnabled;
+    private final int engineVersion;
     private final CreateProjectionOptions options;
 
     public CreateProjection(final GrpcClient client, final String projectionName, final String query,
@@ -22,6 +23,7 @@ public CreateProjection(final GrpcClient client, final String projectionName, fi
         this.query = query;
         this.trackEmittedStreams = options.isTrackingEmittedStreams();
         this.emitEnabled = options.isEmitEnabled();
+        this.engineVersion = options.getEngineVersion();
         this.options = options;
     }
 
@@ -36,6 +38,7 @@ public CompletableFuture execute() {
             Projectionmanagement.CreateReq.Options.Builder optionsBuilder =
                 Projectionmanagement.CreateReq.Options.newBuilder()
                     .setQuery(query)
+                    .setEngineVersion(engineVersion)
                     .setContinuous(continuousBuilder);
 
             Projectionmanagement.CreateReq request = Projectionmanagement.CreateReq.newBuilder()
diff --git a/src/main/java/io/kurrent/dbclient/CreateProjectionOptions.java b/src/main/java/io/kurrent/dbclient/CreateProjectionOptions.java
index 532a87e6..b59f09f9 100644
--- a/src/main/java/io/kurrent/dbclient/CreateProjectionOptions.java
+++ b/src/main/java/io/kurrent/dbclient/CreateProjectionOptions.java
@@ -6,6 +6,7 @@
 public class CreateProjectionOptions extends OptionsBase<CreateProjectionOptions> {
     private boolean trackEmittedStreams;
     private boolean emitEnabled;
+    private int engineVersion;
 
     private CreateProjectionOptions() {
         this.trackEmittedStreams = false;
@@ -26,6 +27,10 @@ boolean isEmitEnabled() {
         return emitEnabled;
     }
 
+    int getEngineVersion() {
+        return engineVersion;
+    }
+
     /**
      * If true, the projection tracks all streams it creates.
      */
@@ -41,4 +46,17 @@ public CreateProjectionOptions emitEnabled(boolean value) {
         this.emitEnabled = value;
         return this;
     }
+
+    /**
+     * Selects the projection engine version. {@code 0} (default) or {@code 1} selects V1;
+     * {@code 2} selects the V2 engine, which provides partition-based parallel processing.
+     * <p>
+     * The engine version is pinned at create time and cannot be changed via update.
+     * V2 has limitations versus V1 — notably, {@code trackEmittedStreams} is rejected,
+     * result streams are not emitted, and bi-state projections are not supported.
+     */
+    public CreateProjectionOptions engineVersion(int value) {
+        this.engineVersion = value;
+        return this;
+    }
 }
diff --git a/src/main/proto/kurrentdb/protocol/v1/projectionmanagement.proto b/src/main/proto/kurrentdb/protocol/v1/projectionmanagement.proto
index b61e940b..2b120e5f 100644
--- a/src/main/proto/kurrentdb/protocol/v1/projectionmanagement.proto
+++ b/src/main/proto/kurrentdb/protocol/v1/projectionmanagement.proto
@@ -28,6 +28,7 @@ message CreateReq {
 			Continuous continuous = 3;
 		}
 		string query = 4;
+		int32 engine_version = 5; // 0 or 1 = v1 (default), 2 = v2
 
 		message Transient {
 			string name = 1;

From c2ea5d8f77ce8345ed0eda7b00fdafa008f09633 Mon Sep 17 00:00:00 2001
From: William Chong <william-chong@outlook.com>
Date: Tue, 5 May 2026 12:40:33 +0400
Subject: [PATCH 2/2] style: replace em dash with colon in javadoc

---
 src/main/java/io/kurrent/dbclient/CreateProjectionOptions.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/main/java/io/kurrent/dbclient/CreateProjectionOptions.java b/src/main/java/io/kurrent/dbclient/CreateProjectionOptions.java
index b59f09f9..5d5a9247 100644
--- a/src/main/java/io/kurrent/dbclient/CreateProjectionOptions.java
+++ b/src/main/java/io/kurrent/dbclient/CreateProjectionOptions.java
@@ -52,7 +52,7 @@ public CreateProjectionOptions emitEnabled(boolean value) {
      * {@code 2} selects the V2 engine, which provides partition-based parallel processing.
      * <p>
      * The engine version is pinned at create time and cannot be changed via update.
-     * V2 has limitations versus V1 — notably, {@code trackEmittedStreams} is rejected,
+     * V2 has limitations versus V1: {@code trackEmittedStreams} is rejected,
      * result streams are not emitted, and bi-state projections are not supported.
      */
     public CreateProjectionOptions engineVersion(int value) {