Fixed mismatch of +/-Infinity replacements when part extracted

Author: alex-kulakov

Orm/Xtensive.Orm.PostgreSql/Sql.Drivers.PostgreSql/v8_0/Compiler.cs

@@ -452,8 +452,8 @@ public override void Visit(SqlExtract node)
         _ = delayedExtractOperations.Add(node);
         (SqlExpression min, SqlExpression max) minMaxValues = ExtractMinMaxValuesForPart(node);
         var @case = SqlDml.Case();
-        @case[node.Operand == Infinity] = minMaxValues.min;
-        @case[node.Operand == NegativeInfinity] = minMaxValues.max;
+        @case[node.Operand == Infinity] = minMaxValues.max;
+        @case[node.Operand == NegativeInfinity] = minMaxValues.min;
         @case.Else = node;
         @case.AcceptVisitor(this);
       }