Use ANSI CROSS JOIN syntax for dialects supporting them instead of implicit join

Author: hazzik

src/NHibernate/Dialect/Dialect.cs

@@ -2635,5 +2635,13 @@ public virtual ISQLExceptionConverter BuildSQLExceptionConverter()
 			// may override to return whatever is most appropriate for that vendor.
 			return new SQLStateConverter(ViolatedConstraintNameExtracter);
 		}
+
+		/// <summary>
+		/// Get the separator to use for definining cross joins when translating HQL queries.
+		/// <para>Typically this will be either [<tt> cross join </tt>] or [<tt>, </tt>]</para>
+		/// <para>Note that the spaces are important!</para>
+		/// </summary>
+		/// <remarks></remarks>
+		public virtual string CrossJoinSeparator => " cross join ";
 	}
 }

src/NHibernate/Dialect/Oracle8iDialect.cs

@@ -34,6 +34,9 @@ public override string AddColumnString
 			get { return "add"; }
 		}
 
+		/// <inheritdoc />
+		public override string CrossJoinSeparator => ", ";
+
 		public override string CascadeConstraintsString
 		{
 			get { return " cascade constraints"; }

src/NHibernate/Dialect/Oracle9iDialect.cs

@@ -20,6 +20,8 @@ public override string CurrentTimestampSQLFunctionName
 			}
 		}
 
+		public override string CrossJoinSeparator => " cross join ";
+
 		// Current_timestamp is a timestamp with time zone, so it can always be converted back to UTC.
 		/// <inheritdoc />
 		public override string CurrentUtcTimestampSQLFunctionName => "SYS_EXTRACT_UTC(current_timestamp)";

src/NHibernate/Dialect/SybaseASE15Dialect.cs

@@ -123,7 +123,9 @@ public override string NullColumnString
 		{
 			get { return " null"; }
 		}
-		
+
+		public override string CrossJoinSeparator => ", ";
+
 		public override bool QualifyIndexName
 		{
 			get { return false; }

src/NHibernate/Hql/Ast/ANTLR/SqlGenerator.cs

@@ -213,10 +213,10 @@ protected virtual void FromFragmentSeparator(IASTNode a)
 			else if (right.RealOrigin == left || (right.RealOrigin != null && right.RealOrigin == left.RealOrigin))
 			{
 				// right represents a joins originating from left; or
-				// both right and left reprersent joins originating from the same FromElement
+				// both right and left represent joins originating from the same FromElement
 				if (right.JoinSequence != null && right.JoinSequence.IsThetaStyle)
 				{
-					Out(", ");
+					WriteCrossJoinSeparator();
 				}
 				else
 				{
@@ -226,10 +226,15 @@ protected virtual void FromFragmentSeparator(IASTNode a)
 			else
 			{
 				// these are just two unrelated table references
-				Out(", ");
+				WriteCrossJoinSeparator();
 			}
 		}
 
+		private void WriteCrossJoinSeparator()
+		{
+			Out(sessionFactory.Dialect.CrossJoinSeparator);
+		}
+
 		protected virtual void NestedFromFragment(IASTNode d, IASTNode parent)
 		{
 			// check a set of parent/child nodes in the from-clause tree
@@ -246,7 +251,7 @@ protected virtual void NestedFromFragment(IASTNode d, IASTNode parent)
 						// right represents a joins originating from left...
 						if (right.JoinSequence != null && right.JoinSequence.IsThetaStyle)
 						{
-							Out(", ");
+							WriteCrossJoinSeparator();
 						}
 						else
 						{
@@ -257,7 +262,7 @@ protected virtual void NestedFromFragment(IASTNode d, IASTNode parent)
 					{
 						// not so sure this is even valid subtree.  but if it was, it'd
 						// represent two unrelated table references...
-						Out(", ");
+						WriteCrossJoinSeparator();
 					}
 				}