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00018 #ifndef PQXX_CACHEDRESULT_H
00019 #define PQXX_CACHEDRESULT_H
00020
00021 #include "pqxx/libcompiler.h"
00022
00023 #include <map>
00024
00025 #include "pqxx/cursor.h"
00026 #include "pqxx/result.h"
00027
00028 namespace pqxx
00029 {
00030
00055 class PQXX_LIBEXPORT cachedresult
00056 {
00057 public:
00058 typedef result::size_type size_type;
00059 typedef size_type blocknum;
00060
00062 typedef result::tuple tuple;
00063
00065 typedef tuple Tuple;
00066
00078 template<typename TRANSACTION> explicit
00079 cachedresult(TRANSACTION &T,
00080 const char Query[],
00081 const PGSTD::string &BaseName="query",
00082 size_type Granularity=100) :
00083 m_Granularity(Granularity),
00084 m_Cache(),
00085 m_Cursor(T, Query, BaseName, Granularity),
00086 m_EmptyResult(),
00087 m_HaveEmpty(false)
00088 {
00089
00090 error_permitted_isolation_level(PQXX_TYPENAME TRANSACTION::isolation_tag());
00091 init();
00092 }
00093
00094
00096
00104 const tuple operator[](size_type i) const
00105 { return GetBlock(BlockFor(i))[Offset(i)]; }
00106
00108
00119 const tuple at(size_type i) const
00120 { return GetBlock(BlockFor(i)).at(Offset(i)); }
00121
00123 size_type size() const;
00124
00126 bool empty() const;
00127
00128 private:
00129 typedef Cursor::pos pos;
00130
00132
00137 static void
00138 error_permitted_isolation_level(isolation_traits<serializable>) throw () {}
00139
00140 void init();
00141
00142 blocknum BlockFor(size_type Row) const throw ()
00143 { return Row / m_Granularity; }
00144 size_type Offset(size_type Row) const throw ()
00145 { return Row % m_Granularity; }
00146 Cursor::size_type FirstRowOf(blocknum Block) const throw ()
00147 { return Block*m_Granularity; }
00148
00149 void MoveTo(blocknum) const;
00150
00152 const result &Fetch() const;
00153
00154 const result &GetBlock(blocknum b) const
00155 {
00156 CacheMap::const_iterator i = m_Cache.find(b);
00157 if (i != m_Cache.end()) return i->second;
00158
00159 MoveTo(b);
00160 return Fetch();
00161 }
00162
00164 size_type m_Granularity;
00165
00166 typedef PGSTD::map<blocknum, result> CacheMap;
00167 mutable CacheMap m_Cache;
00168
00169 mutable Cursor m_Cursor;
00170 mutable result m_EmptyResult;
00171 mutable bool m_HaveEmpty;
00172
00173
00174 cachedresult();
00175 cachedresult(const cachedresult &);
00176 cachedresult &operator=(const cachedresult &);
00177 };
00178
00180 typedef cachedresult CachedResult;
00181
00182 }
00183
00184 #endif
00185