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296 lines
8.8 KiB
Java
296 lines
8.8 KiB
Java
package org.postgresql.fastpath;
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import java.io.*;
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import java.lang.*;
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import java.net.*;
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import java.util.*;
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import java.sql.*;
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import org.postgresql.util.*;
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// Important: There are a lot of debug code commented out. Please do not
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// delete these.
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/*
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* This class implements the Fastpath api.
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*
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* <p>This is a means of executing functions imbeded in the org.postgresql backend
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* from within a java application.
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*
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* <p>It is based around the file src/interfaces/libpq/fe-exec.c
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*
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* @see org.postgresql.FastpathFastpathArg
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* @see org.postgresql.LargeObject
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*/
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public class Fastpath
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{
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// This maps the functions names to their id's (possible unique just
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// to a connection).
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protected Hashtable func = new Hashtable();
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protected org.postgresql.Connection conn; // our connection
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protected org.postgresql.PG_Stream stream; // the network stream
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/*
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* Initialises the fastpath system
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*
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* <p><b>Important Notice</b>
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* <br>This is called from org.postgresql.Connection, and should not be called
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* from client code.
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*
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* @param conn org.postgresql.Connection to attach to
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* @param stream The network stream to the backend
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*/
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public Fastpath(org.postgresql.Connection conn, org.postgresql.PG_Stream stream)
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{
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this.conn = conn;
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this.stream = stream;
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//DriverManager.println("Fastpath initialised");
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}
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/*
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* Send a function call to the PostgreSQL backend
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*
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* @param fnid Function id
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* @param resulttype True if the result is an integer, false for other results
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* @param args FastpathArguments to pass to fastpath
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* @return null if no data, Integer if an integer result, or byte[] otherwise
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* @exception SQLException if a database-access error occurs.
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*/
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public Object fastpath(int fnid, boolean resulttype, FastpathArg[] args) throws SQLException
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{
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// added Oct 7 1998 to give us thread safety
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synchronized (stream)
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{
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// send the function call
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try
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{
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// 70 is 'F' in ASCII. Note: don't use SendChar() here as it adds padding
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// that confuses the backend. The 0 terminates the command line.
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stream.SendInteger(70, 1);
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stream.SendInteger(0, 1);
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stream.SendInteger(fnid, 4);
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stream.SendInteger(args.length, 4);
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for (int i = 0;i < args.length;i++)
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args[i].send(stream);
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// This is needed, otherwise data can be lost
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stream.flush();
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}
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catch (IOException ioe)
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{
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throw new PSQLException("postgresql.fp.send", new Integer(fnid), ioe);
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}
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// Now handle the result
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// We should get 'V' on sucess or 'E' on error. Anything else is treated
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// as an error.
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//int in = stream.ReceiveChar();
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//DriverManager.println("ReceiveChar() = "+in+" '"+((char)in)+"'");
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//if (in!='V') {
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//if (in=='E')
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//throw new SQLException(stream.ReceiveString(conn.getEncoding()));
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//throw new SQLException("Fastpath: expected 'V' from backend, got "+((char)in));
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//}
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// Now loop, reading the results
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Object result = null; // our result
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while (true)
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{
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int in = stream.ReceiveChar();
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//DriverManager.println("ReceiveChar() = "+in+" '"+((char)in)+"'");
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switch (in)
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{
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case 'V':
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break;
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//------------------------------
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// Function returned properly
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//
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case 'G':
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int sz = stream.ReceiveIntegerR(4);
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//DriverManager.println("G: size="+sz); //debug
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// Return an Integer if
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if (resulttype)
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result = new Integer(stream.ReceiveIntegerR(sz));
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else
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{
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byte buf[] = new byte[sz];
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stream.Receive(buf, 0, sz);
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result = buf;
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}
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break;
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//------------------------------
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// Error message returned
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case 'E':
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throw new PSQLException("postgresql.fp.error", stream.ReceiveString(conn.getEncoding()));
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//------------------------------
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// Notice from backend
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case 'N':
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conn.addWarning(stream.ReceiveString(conn.getEncoding()));
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break;
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//------------------------------
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// End of results
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//
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// Here we simply return res, which would contain the result
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// processed earlier. If no result, this already contains null
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case '0':
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//DriverManager.println("returning "+result);
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return result;
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case 'Z':
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break;
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default:
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throw new PSQLException("postgresql.fp.protocol", new Character((char)in));
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}
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}
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}
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}
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/*
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* Send a function call to the PostgreSQL backend by name.
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*
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* Note: the mapping for the procedure name to function id needs to exist,
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* usually to an earlier call to addfunction().
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*
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* This is the prefered method to call, as function id's can/may change
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* between versions of the backend.
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*
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* For an example of how this works, refer to org.postgresql.LargeObject
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*
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* @param name Function name
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* @param resulttype True if the result is an integer, false for other
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* results
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* @param args FastpathArguments to pass to fastpath
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* @return null if no data, Integer if an integer result, or byte[] otherwise
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* @exception SQLException if name is unknown or if a database-access error
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* occurs.
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* @see org.postgresql.LargeObject
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*/
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public Object fastpath(String name, boolean resulttype, FastpathArg[] args) throws SQLException
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{
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//DriverManager.println("Fastpath: calling "+name);
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return fastpath(getID(name), resulttype, args);
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}
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/*
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* This convenience method assumes that the return value is an Integer
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* @param name Function name
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* @param args Function arguments
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* @return integer result
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* @exception SQLException if a database-access error occurs or no result
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*/
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public int getInteger(String name, FastpathArg[] args) throws SQLException
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{
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Integer i = (Integer)fastpath(name, true, args);
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if (i == null)
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throw new PSQLException("postgresql.fp.expint", name);
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return i.intValue();
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}
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/*
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* This convenience method assumes that the return value is an Integer
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* @param name Function name
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* @param args Function arguments
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* @return byte[] array containing result
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* @exception SQLException if a database-access error occurs or no result
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*/
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public byte[] getData(String name, FastpathArg[] args) throws SQLException
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{
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return (byte[])fastpath(name, false, args);
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}
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/*
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* This adds a function to our lookup table.
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*
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* <p>User code should use the addFunctions method, which is based upon a
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* query, rather than hard coding the oid. The oid for a function is not
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* guaranteed to remain static, even on different servers of the same
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* version.
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*
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* @param name Function name
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* @param fnid Function id
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*/
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public void addFunction(String name, int fnid)
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{
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func.put(name, new Integer(fnid));
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}
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/*
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* This takes a ResultSet containing two columns. Column 1 contains the
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* function name, Column 2 the oid.
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*
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* <p>It reads the entire ResultSet, loading the values into the function
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* table.
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*
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* <p><b>REMEMBER</b> to close() the resultset after calling this!!
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*
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* <p><b><em>Implementation note about function name lookups:</em></b>
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*
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* <p>PostgreSQL stores the function id's and their corresponding names in
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* the pg_proc table. To speed things up locally, instead of querying each
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* function from that table when required, a Hashtable is used. Also, only
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* the function's required are entered into this table, keeping connection
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* times as fast as possible.
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*
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* <p>The org.postgresql.LargeObject class performs a query upon it's startup,
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* and passes the returned ResultSet to the addFunctions() method here.
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*
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* <p>Once this has been done, the LargeObject api refers to the functions by
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* name.
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*
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* <p>Dont think that manually converting them to the oid's will work. Ok,
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* they will for now, but they can change during development (there was some
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* discussion about this for V7.0), so this is implemented to prevent any
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* unwarranted headaches in the future.
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*
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* @param rs ResultSet
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* @exception SQLException if a database-access error occurs.
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* @see org.postgresql.LargeObjectManager
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*/
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public void addFunctions(ResultSet rs) throws SQLException
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{
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while (rs.next())
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{
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func.put(rs.getString(1), new Integer(rs.getInt(2)));
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}
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}
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/*
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* This returns the function id associated by its name
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*
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* <p>If addFunction() or addFunctions() have not been called for this name,
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* then an SQLException is thrown.
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*
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* @param name Function name to lookup
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* @return Function ID for fastpath call
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* @exception SQLException is function is unknown.
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*/
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public int getID(String name) throws SQLException
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{
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Integer id = (Integer)func.get(name);
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// may be we could add a lookup to the database here, and store the result
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// in our lookup table, throwing the exception if that fails.
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// We must, however, ensure that if we do, any existing ResultSet is
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// unaffected, otherwise we could break user code.
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//
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// so, until we know we can do this (needs testing, on the TODO list)
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// for now, we throw the exception and do no lookups.
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if (id == null)
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throw new PSQLException("postgresql.fp.unknown", name);
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return id.intValue();
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}
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}
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