This is a means of executing functions imbeded in the postgresql backend - * from within a java application. - * - *
It is based around the file src/interfaces/libpq/fe-exec.c - * - * - *
Implementation notes: - * - *
Network protocol: - * - *
The code within the backend reads integers in reverse. - * - *
There is work in progress to convert all of the protocol to - * network order but it may not be there for v6.3 - * - *
When fastpath switches, simply replace SendIntegerReverse() with - * SendInteger() - * - * @see postgresql.FastpathFastpathArg - * @see postgresql.LargeObject - */ -public class Fastpath -{ - // This maps the functions names to their id's (possible unique just - // to a connection). - protected Hashtable func = new Hashtable(); - - protected postgresql.Connection conn; // our connection - protected postgresql.PG_Stream stream; // the network stream - - /** - * Initialises the fastpath system - * - *
Important Notice
- * It reads the entire ResultSet, loading the values into the function
- * table.
- *
- * REMEMBER to close() the resultset after calling this!!
- *
- * Implementation note about function name lookups:
- *
- * PostgreSQL stores the function id's and their corresponding names in
- * the pg_proc table. To speed things up locally, instead of querying each
- * function from that table when required, a Hashtable is used. Also, only
- * the function's required are entered into this table, keeping connection
- * times as fast as possible.
- *
- * The postgresql.LargeObject class performs a query upon it's startup,
- * and passes the returned ResultSet to the addFunctions() method here.
- *
- * Once this has been done, the LargeObject api refers to the functions by
- * name.
- *
- * Dont think that manually converting them to the oid's will work. Ok,
- * they will for now, but they can change during development (there was some
- * discussion about this for V7.0), so this is implemented to prevent any
- * unwarranted headaches in the future.
- *
- * @param rs ResultSet
- * @exception SQLException if a database-access error occurs.
- * @see postgresql.LargeObjectManager
- */
- public void addFunctions(ResultSet rs) throws SQLException
- {
- while(rs.next()) {
- func.put(rs.getString(1),new Integer(rs.getInt(2)));
- }
- }
-
- /**
- * This returns the function id associated by its name
- *
- * If addFunction() or addFunctions() have not been called for this name,
- * then an SQLException is thrown.
- *
- * @param name Function name to lookup
- * @return Function ID for fastpath call
- * @exception SQLException is function is unknown.
- */
- public int getID(String name) throws SQLException
- {
- Integer id = (Integer)func.get(name);
-
- // may be we could add a lookup to the database here, and store the result
- // in our lookup table, throwing the exception if that fails.
- // We must, however, ensure that if we do, any existing ResultSet is
- // unaffected, otherwise we could break user code.
- //
- // so, until we know we can do this (needs testing, on the TODO list)
- // for now, we throw the exception and do no lookups.
- if(id==null)
- throw new PSQLException("postgresql.fp.unknown",name);
-
- return id.intValue();
- }
-}
-
--
cgit v1.2.3
This is called from postgresql.Connection, and should not be called
- * from client code.
- *
- * @param conn postgresql.Connection to attach to
- * @param stream The network stream to the backend
- */
- public Fastpath(postgresql.Connection conn,postgresql.PG_Stream stream)
- {
- this.conn=conn;
- this.stream=stream;
- //DriverManager.println("Fastpath initialised");
- }
-
- /**
- * Send a function call to the PostgreSQL backend
- *
- * @param fnid Function id
- * @param resulttype True if the result is an integer, false for other results
- * @param args FastpathArguments to pass to fastpath
- * @return null if no data, Integer if an integer result, or byte[] otherwise
- * @exception SQLException if a database-access error occurs.
- */
- public Object fastpath(int fnid,boolean resulttype,FastpathArg[] args) throws SQLException
- {
- // added Oct 7 1998 to give us thread safety
- synchronized(stream) {
-
- // send the function call
- try {
- // 70 is 'F' in ASCII. Note: don't use SendChar() here as it adds padding
- // that confuses the backend. The 0 terminates the command line.
- stream.SendInteger(70,1);
- stream.SendInteger(0,1);
-
- //stream.SendIntegerReverse(fnid,4);
- //stream.SendIntegerReverse(args.length,4);
- stream.SendInteger(fnid,4);
- stream.SendInteger(args.length,4);
-
- for(int i=0;i