[oracle] Prefetch memory variable changed to 32-bit and default raise…

…d to 8MB

Speeds up oracle table access by orders of magnitude

(cherry-pick from commit c3e7632)

Author :     Björn Harrtell <bjorn@wololo.org>
Date :       Mon Oct 29 21:27:46 2018 +0100

src/providers/oracle/ocispatial/qsql_ocispatial.cpp

@@ -86,8 +86,8 @@
 #include <stdlib.h>
 
 #define QOCISPATIAL_DYNAMIC_CHUNK_SIZE 65535
-#define QOCISPATIAL_PREFETCH_MEM  10240
-
+#define QOCISPATIAL_PREFETCH_ROWS  10000
+#define QOCISPATIAL_PREFETCH_MEM  8388608 // 8MB
 // setting this define will allow using a query from a different
 // thread than its database connection.
 // warning - this is not fully tested and can lead to race conditions
@@ -355,7 +355,7 @@ struct QOCISpatialResultPrivate
   QList<QOCISDOGeometryInd*> sdoind;
   bool transaction;
   int serverVersion;
-  int prefetchRows, prefetchMem;
+  ub4 prefetchRows, prefetchMem;
   OCIType *geometryTDO;
   QOCISDOGeometryObj *geometryObj;
   QOCISDOGeometryInd *geometryInd;
@@ -765,7 +765,7 @@ struct QOCISpatialDriverPrivate
   bool transaction;
   int serverVersion;
   ub4 prefetchRows;
-  ub2 prefetchMem;
+  ub4 prefetchMem;
   QString user;
 
   OCIType *geometryTDO;
@@ -782,7 +782,7 @@ QOCISpatialDriverPrivate::QOCISpatialDriverPrivate()
     , err( 0 )
     , transaction( false )
     , serverVersion( -1 )
-    , prefetchRows( 0xffffffff )
+    , prefetchRows( QOCISPATIAL_PREFETCH_ROWS )
     , prefetchMem( QOCISPATIAL_PREFETCH_MEM )
     , geometryTDO( 0 )
 {
@@ -3381,13 +3381,13 @@ static void qParseOpts( const QString &options, QOCISpatialDriverPrivate *d )
     {
       d->prefetchRows = val.toInt( &ok );
       if ( !ok )
-        d->prefetchRows = 0xffffffff;
+        d->prefetchRows = QOCISPATIAL_PREFETCH_ROWS;
     }
     else if ( opt == QLatin1String( "OCI_ATTR_PREFETCH_MEMORY" ) )
     {
       d->prefetchMem = val.toInt( &ok );
       if ( !ok )
-        d->prefetchMem = 0xffff;
+        d->prefetchMem = QOCISPATIAL_PREFETCH_MEM;
     }
     else
     {