mariadb/sql/sql_cte.h

#ifndef SQL_CTE_INCLUDED
#define SQL_CTE_INCLUDED
#include "sql_list.h"
#include "sql_lex.h"

class With_clause;

/**
  @class With_clause
  @brief Set of with_elements

  It has a reference to the first with element from this with clause.
  This reference allows to navigate through all the elements of the with clause.
  It contains a reference to the unit to which this with clause is attached.
  It also contains a flag saying whether this with clause was specified as recursive.
*/ 

class With_element : public Sql_alloc
{
private:
  With_clause *owner;      // with clause this object belongs to
  With_element *next_elem; // next element in the with clause
  uint number;  // number of the element in the with clause (starting from 0)
  /* 
    The map dependency_map has 1 in the i-th position if the query that
    specifies this element contains a reference to the element number i
    in the query FROM list.
  */
  table_map elem_map;  // The map where with only one 1 set in this->number   
  table_map dependency_map;
  /* 
    Total number of references to this element in the FROM lists of
    the queries that are in the scope of the element (including
    subqueries and specifications of other with elements).
  */ 
  uint references;
  /* 
    Unparsed specification of the query that specifies this element.
    It used to build clones of the specification if they are needed.
  */
  LEX_STRING unparsed_spec;

  /* Return the map where 1 is set only in the position for this element */
  table_map get_elem_map() { return 1 << number; }
 
public:
  /*
    The name of the table introduced by this with elememt. The name
     can be used in FROM lists of the queries in the scope of the element.
  */
  LEX_STRING *query_name;
  /*
    Optional list of column names to name the columns of the table introduced
    by this with element. It is used in the case when the names are not
    inherited from the query that specified the table. Otherwise the list is
    always empty.
  */
  List <LEX_STRING> column_list;
  /* The query that specifies the table introduced by this with element */
  st_select_lex_unit *spec;
  /* 
    Set to true is recursion is used (directly or indirectly)
    for the definition of this element
  */
  bool is_recursive;

  With_element(LEX_STRING *name,
               List <LEX_STRING> list,
               st_select_lex_unit *unit)
    : next_elem(NULL), dependency_map(0), references(0),
      query_name(name), column_list(list), spec(unit),
      is_recursive(false) {}

  void check_dependencies_in_unit(st_select_lex_unit *unit);

  void  set_dependency_on(With_element *with_elem)
  { dependency_map|= with_elem->get_elem_map(); }

  bool check_dependency_on(With_element *with_elem)
  { return dependency_map & with_elem->get_elem_map(); }

  bool set_unparsed_spec(THD *thd, char *spec_start, char *spec_end);

  st_select_lex_unit *clone_parsed_spec(THD *thd, TABLE_LIST *with_table);

  bool is_referenced() { return references != 0; }

  void inc_references() { references++; }

  bool rename_columns_of_derived_unit(THD *thd, st_select_lex_unit *unit);

  bool prepare_unreferenced(THD *thd);

  void print(String *str, enum_query_type query_type);

  friend class With_clause;
};


/**
  @class With_element
  @brief Definition of a CTE table
	
  It contains a reference to the name of the table introduced by this with element,
  and a reference to the unit that specificies this table. Also it contains
  a reference to the with clause to which this element belongs to.	
*/

class With_clause : public Sql_alloc
{
private:
  st_select_lex_unit *owner; // the unit this with clause attached to
  With_element *first_elem; // the first definition in this with clause 
  With_element **last_next; // here is set the link for the next added element
  uint elements; // number of the elements/defintions in this with clauses 
  /*
    The with clause immediately containing this with clause if there is any,
    otherwise NULL. Now used  only at parsing.
  */
  With_clause *embedding_with_clause;
  /*
    The next with the clause of the chain of with clauses encountered
    in the current statement
  */
  With_clause *next_with_clause;
  /* Set to true if dependencies between with elements have been checked */
  bool dependencies_are_checked; 

public:
 /* If true the specifier RECURSIVE is present in the with clause */
  bool with_recursive;

  With_clause(bool recursive_fl, With_clause *emb_with_clause)
    : owner(NULL), first_elem(NULL), elements(0),
      embedding_with_clause(emb_with_clause), next_with_clause(NULL),
    dependencies_are_checked(false),
      with_recursive(recursive_fl)
  { last_next= &first_elem; }

  /* Add a new element to the current with clause */ 
  bool add_with_element(With_element *elem)
  { 
    elem->owner= this;
    elem->number= elements;
    owner= elem->spec;
    owner->with_element= elem;
    *last_next= elem;
    last_next= &elem->next_elem;
    elements++;
    return false;
  }

  /* Add this with clause to the list of with clauses used in the statement */
  void add_to_list(With_clause ** &last_next)
  {
    *last_next= this;
    last_next= &this->next_with_clause;
  }

  With_clause *pop() { return embedding_with_clause; }
      
  bool check_dependencies();

  With_element *find_table_def(TABLE_LIST *table);

  With_element *find_table_def_in_with_clauses(TABLE_LIST *table);

  bool prepare_unreferenced_elements(THD *thd);

  void print(String *str, enum_query_type query_type);

  friend
  bool check_dependencies_in_with_clauses(With_clause *with_clauses_list);

};


#endif /* SQL_CTE_INCLUDED */