Parser Modification Problem: Get the columns of a Table

Dear Friends,

I am trying to modify the parser of the postgresql so as to print all the columns of a table (or to put them in a seperate file) when the parser meets an Insert Statement.
In the <gram.y> file (/src/backend/parser/gram.y) ,

InsertStmt:
INSERT INTO qualified_name insert_rest
{
$4->relation = $3;
$$ = (Node *) $4;
}
;
I can take the table name adding the following line of code

printf($3->relname);


The problem is that in the insert_column_item section (see the last section below) the var n is of type ResTarget and in case of insert and select the ResTarget->Name is null and not the name of the column (in the update command everything is ok- see also the line 371 in the file parsenodes.h ...typedef struct ResTarget {....} ). Could you please tell me the way to take the names of the columns?

Every answer will be appreciated
Thank You Very Much In Advance
NK
noc100(at)yahoo(dot)gr

insert_rest:
VALUES '(' insert_target_list ')'
{
$$ = makeNode(InsertStmt);
$$->cols = NIL;
$$->targetList = $3;
$$->selectStmt = NULL;
}
| DEFAULT VALUES
{
$$ = makeNode(InsertStmt);
$$->cols = NIL;
$$->targetList = NIL;
$$->selectStmt = NULL;
}
| SelectStmt
{
$$ = makeNode(InsertStmt);
$$->cols = NIL;
$$->targetList = NIL;
$$->selectStmt = $1;
}
| '(' insert_column_list ')' VALUES '(' insert_target_list ')'
{
$$ = makeNode(InsertStmt);
$$->cols = $2;
$$->targetList = $6;
$$->selectStmt = NULL;
}
| '(' insert_column_list ')' SelectStmt
{
$$ = makeNode(InsertStmt);
$$->cols = $2;
$$->targetList = NIL;
$$->selectStmt = $4;
}
;
insert_column_list:
insert_column_item { $$ = makeList1($1); }
| insert_column_list ',' insert_column_item
{ $$ = lappend($1, $3); }
;
insert_column_item:
ColId opt_indirection
{
ResTarget *n = makeNode(ResTarget);
n->name = $1;
n->indirection = $2;
n->val = NULL;
$$ = (Node *)n;
}
;

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