From 3b6ed3bfc81ae079fd30b3a382f11c2435bdddd5 Mon Sep 17 00:00:00 2001
From: Alvaro Huarte <ahuarte47@yahoo.es>
Date: Fri, 27 Dec 2013 09:21:22 +0100
Subject: [PATCH] #8725-R: PostgresProvider simplifies on provider side

PostgresFeatureIterator implements simplification on provider side
---
 .../postgres/qgspostgresfeatureiterator.cpp   | 49 +++++++++++++++++++
 .../postgres/qgspostgresfeatureiterator.h     |  3 ++
 .../postgres/qgspostgresprovider.cpp          |  3 ++
 3 files changed, 55 insertions(+)

diff --git a/src/providers/postgres/qgspostgresfeatureiterator.cpp b/src/providers/postgres/qgspostgresfeatureiterator.cpp
index 6c088ab4452a..47054cb43d5a 100644
--- a/src/providers/postgres/qgspostgresfeatureiterator.cpp
+++ b/src/providers/postgres/qgspostgresfeatureiterator.cpp
@@ -80,6 +80,9 @@ QgsPostgresFeatureIterator::QgsPostgresFeatureIterator( QgsPostgresProvider* p,
     return;
   }
 
+  //setup if required the simplification of geometries to fetch
+  prepareProviderSimplification();
+
   mFetched = 0;
 }
 
@@ -170,6 +173,26 @@ bool QgsPostgresFeatureIterator::fetchFeature( QgsFeature& feature )
   return true;
 }
 
+bool QgsPostgresFeatureIterator::prepareProviderSimplification()
+{
+  const QgsSimplifyMethod& simplifyMethod = mRequest.simplifyMethod();
+
+  // validate settings of simplification of geometries to fetch
+  if ( simplifyMethod.methodType() != QgsSimplifyMethod::NoSimplification && !simplifyMethod.forceLocalOptimization() && !( mRequest.flags() & QgsFeatureRequest::NoGeometry ) )
+  {
+    QgsSimplifyMethod::MethodType methodType = simplifyMethod.methodType();
+
+    if ( methodType == QgsSimplifyMethod::OptimizeForRendering || methodType == QgsSimplifyMethod::PreserveTopology )
+    {
+      return true;
+    }
+    else
+    {
+      QgsDebugMsg( QString( "Simplification method type (%1) is not recognised by PostgresFeatureIterator" ).arg( methodType ) );
+    }
+  }
+  return false;
+}
 
 bool QgsPostgresFeatureIterator::rewind()
 {
@@ -272,8 +295,34 @@ bool QgsPostgresFeatureIterator::declareCursor( const QString& whereClause )
 
   try
   {
+    const QgsSimplifyMethod& simplifyMethod = mRequest.simplifyMethod();
+
     QString query = "SELECT ", delim = "";
 
+    if ( mFetchGeometry && !simplifyMethod.forceLocalOptimization() && simplifyMethod.methodType() != QgsSimplifyMethod::NoSimplification )
+    {
+      QString simplifyFunctionName = simplifyMethod.methodType() == QgsSimplifyMethod::OptimizeForRendering 
+               ?
+              ( P->mConnectionRO->majorVersion() < 2 ? "simplify" : "st_simplify" )
+               :
+              ( P->mConnectionRO->majorVersion() < 2 ? "simplifypreservetopology" : "st_simplifypreservetopology" );
+
+      double tolerance = simplifyMethod.methodType() == QgsSimplifyMethod::OptimizeForRendering 
+               ?
+               simplifyMethod.tolerance() / 5.0f /* experimental */
+               :
+               simplifyMethod.tolerance();
+
+      query += QString( "%1(%5(%2%3,%6),'%4')" )
+               .arg( P->mConnectionRO->majorVersion() < 2 ? "asbinary" : "st_asbinary" )
+               .arg( P->quotedIdentifier( P->mGeometryColumn ) )
+               .arg( P->mSpatialColType == sctGeography ? "::geometry" : "" )
+               .arg( P->endianString() )
+               .arg( simplifyFunctionName )
+               .arg( tolerance );
+      delim = ",";
+    }
+    else
     if ( mFetchGeometry )
     {
       query += QString( "%1(%2%3,'%4')" )
diff --git a/src/providers/postgres/qgspostgresfeatureiterator.h b/src/providers/postgres/qgspostgresfeatureiterator.h
index a69d63a9c368..b4ba18716d51 100644
--- a/src/providers/postgres/qgspostgresfeatureiterator.h
+++ b/src/providers/postgres/qgspostgresfeatureiterator.h
@@ -40,6 +40,9 @@ class QgsPostgresFeatureIterator : public QgsAbstractFeatureIterator
     //! fetch next feature, return true on success
     virtual bool fetchFeature( QgsFeature& feature );
 
+    //! setup if required the simplification of geometries to fetch, it uses the settings of current FeatureRequest
+    virtual bool prepareProviderSimplification();
+
     QgsPostgresProvider* P;
 
     QString whereClauseRect();
diff --git a/src/providers/postgres/qgspostgresprovider.cpp b/src/providers/postgres/qgspostgresprovider.cpp
index dd97bf14bb8a..a6d1574b3fad 100644
--- a/src/providers/postgres/qgspostgresprovider.cpp
+++ b/src/providers/postgres/qgspostgresprovider.cpp
@@ -993,6 +993,9 @@ bool QgsPostgresProvider::hasSufficientPermsAndCapabilities()
     }
   }
 
+  // supports geometry simplification on provider side
+  mEnabledCapabilities |= QgsVectorDataProvider::SimplifyGeometries;
+
   return true;
 }