Remove superfluous includes; forward declare wherever possible

Author: pranavk

src/include/network/postgres_protocol_handler.h

@@ -24,7 +24,6 @@
 #include "common/statement.h"
 #include "common/statement_cache.h"
 #include "traffic_cop/traffic_cop.h"
-#include "parser/postgresparser.h"
 #include "protocol_handler.h"
 #include "traffic_cop/traffic_cop.h"
 
@@ -33,6 +32,10 @@
 
 namespace peloton {
 
+namespace parser {
+    class ExplainStatement;
+}
+
 namespace network {
 
 typedef std::vector<std::unique_ptr<OutputPacket>> ResponseBuffer;

src/include/parser/explain_statement.h

@@ -12,13 +12,12 @@
 
 #pragma once
 
-#include "common/logger.h"
-#include "common/sql_node_visitor.h"
-#include "expression/abstract_expression.h"
 #include "parser/sql_statement.h"
-#include "parser/table_ref.h"
 
 namespace peloton {
+
+class SqlNodeVisitor;
+
 namespace parser {
 
 /**
@@ -31,7 +30,7 @@ class ExplainStatement : public SQLStatement {
       : SQLStatement(StatementType::EXPLAIN) {}
   virtual ~ExplainStatement() {}
 
-  virtual void Accept(SqlNodeVisitor* /*v*/) override { }
+  virtual void Accept(UNUSED_ATTRIBUTE SqlNodeVisitor* v) override { }
 
   std::unique_ptr<parser::SQLStatement> real_sql_stmt;
 };

src/network/postgres_protocol_handler.cpp

@@ -23,6 +23,7 @@
 #include "network/postgres_protocol_handler.h"
 #include "network/peloton_server.h"
 #include "parser/postgresparser.h"
+#include "parser/statements.h"
 #include "planner/abstract_plan.h"
 #include "planner/delete_plan.h"
 #include "planner/insert_plan.h"