query.h

一个功能强大的内存数据库源代码,c++编写,有详细的注释

//-< QUERY.H >-------------------------------------------------------*--------*
// FastDB                    Version 1.0         (c) 1999  GARRET    *     ?  *
// (Main Memory Database Management System)                          *   /\|  *
//                                                                   *  /  \  *
//                          Created:     20-Nov-98    K.A. Knizhnik  * / [] \ *
//                          Last update: 10-Dec-98    K.A. Knizhnik  * GARRET *
//-------------------------------------------------------------------*--------*
// Constructing and hashing database query statements
//-------------------------------------------------------------------*--------*

#ifndef __QUERY_H__
#define __QUERY_H__

/**
 * Element of the query
 */
class FASTDB_DLL_ENTRY dbQueryElement { 
    friend class dbQuery;
    friend class dbCompiler;
    friend class dbQueryExpression;
    friend class dbQueryElementAllocator;
  public:
    enum ElementType { 
	qExpression, // part of SQL expression
	qVarBool,
	qVarInt1,
	qVarInt2,
	qVarInt4,
	qVarInt8,
	qVarReal4,
	qVarReal8,
	qVarString,
	qVarStringPtr,
	qVarReference,
	qVarArrayOfRef,	
	qVarArrayOfRefPtr,
	qVarRawData
#ifdef USE_STD_STRING
	,qVarStdString
#endif
    };
    
    void* operator new (size_t size);
    void  operator delete(void* p);

    char* dump(char* buf);
    char* dumpValues(char* buf);

    dbQueryElement(ElementType t, void const* p, 
		   dbTableDescriptor* table = NULL) 
    {
	type = t;
	ptr  = p; 	
	ref  = table;
	next = NULL;
    } 
  private:
    dbQueryElement*    next;
    void const*        ptr;
    ElementType        type;
    dbTableDescriptor* ref;
};


/**
 * Allocator of query elements. This class links deallocated elements in the list of free elements,
 * and reused them in future. So number of system memory allocator invocations is dramatically reduced.
 * Cleanup of free elements lst is performed by <code>dbDatabase::cleanup()</code> method
 */
class FASTDB_DLL_ENTRY dbQueryElementAllocator { 
    friend class dbDatabase;

    dbMutex&        mutex;
    dbQueryElement* freeChain;
    
  public:
    void deallocate(dbQueryElement* first, dbQueryElement** lastNext) { 
	dbCriticalSection cs(mutex);
	if (first != NULL) { 
	    *lastNext = freeChain;
	    freeChain = first;
	}
    }
	
    void* allocate(size_t size);

    dbQueryElementAllocator();
    ~dbQueryElementAllocator();

    static dbQueryElementAllocator instance;
};

inline void* dbQueryElement::operator new(size_t size) {
    return dbQueryElementAllocator::instance.allocate(size);
}

/**
 * This class represents component of the structure.
 * It is mostly needed for implementation of application specific database types. For example, look at
 * <code>dbDate</code> class. It contains <code>int4 jday</code> component which stores time in seconds sinse 1970.
 * This class defines its own comparison methods:
 * <PRE>
 *     dbQueryExpression operator == (char const* field) { 
 *	   dbQueryExpression expr;
 *	   expr = dbComponent(field,"jday"),"=",jday;
 *    	   return expr;
 *     }
 * </PRE>
 * Making it possible to sepcify queries like this (assume that record has column "released" with type dbDate:
 * <PRE>
 *     dbQuery q;
 *     dbDate  date;
 *     q = date == "released";
 * </PRE>
 */
class FASTDB_DLL_ENTRY dbComponent { 
  public:
    char const* structure;
    char const* field; 

    dbComponent(char const* s, char const* f=NULL) : structure(s), field(f) {}
};


/**
 * Class representing SubSQL expression.  
 * It is mostly needed for implementation of application specific database types.
 * Look at the example in dbComponent class. 
 * The effect of addeing dbExpression to the query is the same as if this expresion is enclosed in parenthesis.
 */
class FASTDB_DLL_ENTRY dbQueryExpression { 
    friend class dbQuery;
    dbQueryElement*  first;
    dbQueryElement** last;
    bool             operand;

  public:
    dbQueryExpression& add(dbQueryElement::ElementType type, void const* ptr, dbTableDescriptor* table = NULL) {
	last = &(*last = new dbQueryElement(type, ptr, table))->next;
	operand = (type == dbQueryElement::qExpression);
	return *this;
    }
	
    dbQueryExpression& operator = (char const* ptr) { 
	first = NULL, last = &first;
	return add(dbQueryElement::qExpression, ptr);
    }
    dbQueryExpression& operator = (dbComponent const& comp);

    dbQueryExpression& operator = (dbQueryExpression const& expr);

    dbQueryExpression& operator,(int1 const& ptr) { 
        return add(dbQueryElement::qVarInt1, &ptr);
    }
    dbQueryExpression& operator,(int2 const& ptr) { 
        return add(dbQueryElement::qVarInt2, &ptr);
    }
    dbQueryExpression& operator,(int4 const& ptr) { 
        return add(dbQueryElement::qVarInt4, &ptr);
    }
    dbQueryExpression& operator,(db_int8 const& ptr) { 
        return add(dbQueryElement::qVarInt8, &ptr);
    }
    dbQueryExpression& operator,(real4 const& ptr) { 
        return add(dbQueryElement::qVarReal4, &ptr);
    }
    dbQueryExpression& operator,(real8 const& ptr) { 
        return add(dbQueryElement::qVarReal8, &ptr);
    }
    dbQueryExpression& operator,(bool const& ptr) { 
        return add(dbQueryElement::qVarBool, &ptr);
    }
    dbQueryExpression& operator,(char const* ptr) { 
        return add(operand ? dbQueryElement::qVarString 
		   : dbQueryElement::qExpression, ptr);
    }
    dbQueryExpression& operator,(char const** ptr) { 
        return add(dbQueryElement::qVarStringPtr, ptr);
    }
    dbQueryExpression& operator,(char** ptr) { 
        return add(dbQueryElement::qVarStringPtr, ptr);
    }
    dbQueryExpression& operator,(void const* ptr) { 
 	return add(dbQueryElement::qVarRawData, ptr);
     }
#ifdef USE_STD_STRING
    dbQueryExpression& operator,(std::string const& str) {
        return add(dbQueryElement::qVarStdString, &str);
    }
#endif
    dbQueryExpression& operator,(dbQueryExpression const& expr) { 
	*last = new dbQueryElement(dbQueryElement::qExpression, "(");
	(*last)->next = expr.first;
	last = expr.last;
	*last = new dbQueryElement(dbQueryElement::qExpression, ")");
	last = &(*last)->next;
	operand = false;
	return *this;
    }
    dbQueryExpression& operator,(dbComponent const& comp) { 
	add(dbQueryElement::qExpression, comp.structure);
	if (comp.field != NULL) { 
	    add(dbQueryElement::qExpression, ".");
	    add(dbQueryElement::qExpression, comp.field);
	}
	operand = false;
	return *this;
    }
    dbQueryExpression& operator += (dbComponent const& comp) { 
        return *this,comp;
    }
    dbQueryExpression& operator += (char const* ptr) { 
	return add(dbQueryElement::qExpression, ptr);
    }
#ifndef NO_MEMBER_TEMPLATES
    template<class T>
    dbQueryExpression& operator,(dbReference<T> const& value) { 
	return add(dbQueryElement::qVarReference, &value, &T::dbDescriptor);
    }

    template<class T>
    inline dbQueryExpression& operator,(dbArray< dbReference<T> > const& value) { 
	return add(dbQueryElement::qVarArrayOfRef, &value, 
		      &T::dbDescriptor);
    }

    template<class T>
    inline dbQueryExpression& operator,(dbArray< dbReference<T> >const* const& value) { 
 	return add(dbQueryElement::qVarArrayOfRefPtr, &value, &T::dbDescriptor);
    }
#endif
};

class dbOrderByNode;
class dbFollowByNode;


/**
 * Class used for precompiled queries
 */
class FASTDB_DLL_ENTRY dbCompiledQuery { 
  public:
    dbExprNode*        tree;
    dbOrderByNode*     order;
    dbFollowByNode*    follow;
    dbTableDescriptor* table;
    
    enum IteratorInit { 
	StartFromAny,
	StartFromFirst,
	StartFromLast,
	StartFromRef, 
	StartFromArray,
	StartFromArrayPtr
    };
    IteratorInit       startFrom;
    void const*        root;

    void destroy();

    bool compiled() { return tree != NULL; }

    dbCompiledQuery() { 
	tree = NULL;
	order = NULL;
	follow = NULL;
	table = NULL;
	startFrom = StartFromAny;
    }
};

/**
 * Query class. It is derived from <code>dbCompiledQuery</code> class because each query is compiled only once - when
 * it is executed first time. All subsequent executions of query used precompiled tree.
 */
class FASTDB_DLL_ENTRY dbQuery : public dbCompiledQuery { 
    friend class dbCompiler;
    friend class dbDatabase;
    friend class dbSubSql;
  private:
    dbMutex            mutex;
    dbQueryElement*    elements;
    dbQueryElement**   nextElement;
    bool               operand;
    bool               mutexLocked;

    //
    // Prohibite query copying
    //
    dbQuery(dbQuery const&) {} 
    dbQuery& operator =(dbQuery const&) { return *this; }

  public:
    int                pos; // position of condition in statement


    char* dump(char* buf) { 
	char* p = buf;
	for (dbQueryElement* elem = elements; elem != NULL; elem = elem->next) { 
	    p = elem->dump(p);
	}
	return buf;
    }

    char* dumpValues(char* buf) { 
	char* p = buf;
	for (dbQueryElement* elem = elements; elem != NULL; elem = elem->next) { 
	    p = elem->dumpValues(p);
	}
	return buf;
    }

    dbQuery& append(dbQueryElement::ElementType type, void const* ptr,
		    dbTableDescriptor* table = NULL) 
    { 
	nextElement = &(*nextElement=new dbQueryElement(type,ptr,table))->next;
	operand = (type == dbQueryElement::qExpression);
	return *this;
    }

    dbQuery& reset();

    //
    // Redefined operator = and , make it possible to specify query in the
    // following way:
    //         int x, y;
    //         dbDataTime dt;
    //         dbQuery q; 
    //         dbCursor<record> cursor;
    //         q = "x=",x,"and y=",y,"and",dt == "date";
    //         for (x = 0; x < max_x; x++) { 
    //             for (y = 0; y < max_y; y++) { 
    //                 cursor.select(q);
    //                 ...
    //             }
    //         }

    dbQuery& add(dbQueryExpression const& expr); 

    dbQuery& And(char const* str) { 
	if (elements != NULL) { 
	    append(dbQueryElement::qExpression, "and");
	}
	return append(dbQueryElement::qExpression, str);
    }

    dbQuery& Or(char const* str) { 
	if (elements != NULL) { 
	    append(dbQueryElement::qExpression, "or");
	}
	return append(dbQueryElement::qExpression, str);
    }

    dbQuery& add(char const* str) { 
	return append(operand ? dbQueryElement::qVarString