Allow the disabling of websocket updates (#1726)

The websocket updates (for the live updates of the "Analysis" tree) can significantly slow down queries with very many cheap operations. This change adds a runtime parameter `websocket-updates-enabled` for controlling whether websocket updates should be performed or not.

src/engine/Operation.cpp

@@ -598,7 +598,7 @@ const vector<ColumnIndex>& Operation::getResultSortedOn() const {
 // _____________________________________________________________________________
 
 void Operation::signalQueryUpdate() const {
-  if (_executionContext) {
+  if (_executionContext && _executionContext->areWebsocketUpdatesEnabled()) {
     _executionContext->signalQueryUpdate(*_rootRuntimeInfo);
   }
 }

src/engine/QueryExecutionContext.h

@@ -5,6 +5,8 @@
 
 #pragma once
 
+#include <global/RuntimeParameters.h>
+
 #include <memory>
 #include <string>
 
@@ -143,6 +145,12 @@ class QueryExecutionContext {
   bool _pinSubtrees;
   bool _pinResult;
 
+  // If false, then no updates of the runtime information should be sent via the
+  // websocket connection for performance reasons.
+  bool areWebsocketUpdatesEnabled() const {
+    return areWebsocketUpdatesEnabled_;
+  }
+
  private:
   const Index& _index;
 
@@ -158,4 +166,8 @@ class QueryExecutionContext {
   QueryPlanningCostFactors _costFactors;
   SortPerformanceEstimator _sortPerformanceEstimator;
   std::function<void(std::string)> updateCallback_;
+  // Cache the state of that runtime parameter to reduce the contention of the
+  // mutex.
+  bool areWebsocketUpdatesEnabled_ =
+      RuntimeParameters().get<"websocket-updates-enabled">();
 };

src/global/RuntimeParameters.h

@@ -20,6 +20,7 @@ inline auto& RuntimeParameters() {
   // clearly misunderstand something about static initialization.
   static ad_utility::Parameters params = []() {
     using namespace std::chrono_literals;
+    using namespace ad_utility::memory_literals;
     auto ensureStrictPositivity = [](auto&& parameter) {
       parameter.setParameterConstraint(
           [](std::chrono::seconds value, std::string_view parameterName) {
@@ -54,6 +55,7 @@ inline auto& RuntimeParameters() {
         // Control up until which size lazy results should be cached. Caching
         // does cause significant overhead for this case.
         MemorySizeParameter<"lazy-result-max-cache-size">{5_MB},
+        Bool<"websocket-updates-enabled">{true},
         // When the result of an index scan is smaller than a single block, then
         // its size estimate will be the size of the block divided by this
         // value.