iss-581: move exists omit to compiler

Author: ahmad-moussawi

QueryBuilder/Base.Where.cs

@@ -539,10 +539,6 @@ public Q WhereExists(Query query)
                 throw new ArgumentException($"'{nameof(FromClause)}' cannot be empty if used inside a '{nameof(WhereExists)}' condition");
             }
 
-            // remove unneeded components
-            query = query.Clone().ClearComponent("select")
-                .SelectRaw("1");
-
             return AddComponent("where", new ExistsCondition
             {
                 Query = query,

QueryBuilder/Compilers/Compiler.Conditions.cs

@@ -247,7 +247,16 @@ protected virtual string CompileExistsCondition(SqlResult ctx, ExistsCondition i
         {
             var op = item.IsNot ? "NOT EXISTS" : "EXISTS";
 
-            var subCtx = CompileSelectQuery(item.Query);
+
+            // remove unneeded components
+            var query = item.Query.Clone();
+
+            if (OmitSelectInsideExists)
+            {
+                query.ClearComponent("select").SelectRaw("1");
+            }
+
+            var subCtx = CompileSelectQuery(query);
 
             ctx.Bindings.AddRange(subCtx.Bindings);