org.postgresql.fastpath.Fastpath Maven / Gradle / Ivy
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/*-------------------------------------------------------------------------
*
* Copyright (c) 2003-2011, PostgreSQL Global Development Group
*
* IDENTIFICATION
* $PostgreSQL: pgjdbc/org/postgresql/fastpath/Fastpath.java,v 1.37 2011/08/02 13:42:25 davecramer Exp $
*
*-------------------------------------------------------------------------
*/
package org.postgresql.fastpath;
import java.sql.SQLException;
import java.sql.ResultSet;
import java.util.Hashtable;
import org.postgresql.core.BaseConnection;
import org.postgresql.core.QueryExecutor;
import org.postgresql.core.ParameterList;
import org.postgresql.util.PSQLException;
import org.postgresql.util.PSQLState;
import org.postgresql.util.GT;
/**
* This class implements the Fastpath api.
*
* This is a means of executing functions embedded in the
* backend from within a java application.
*
*
It is based around the file src/interfaces/libpq/fe-exec.c
*
*/
public class Fastpath
{
// Java passes oids around as longs, but in the backend
// it's an unsigned int, so we use this to make the conversion
// of long -> signed int which the backend interprets as unsigned.
private final static long NUM_OIDS = 4294967296L; // 2^32
// This maps the functions names to their id's (possible unique just
// to a connection).
private final Hashtable func = new Hashtable();
private final QueryExecutor executor;
private final BaseConnection connection;
/**
* Initialises the fastpath system
*
* @param conn BaseConnection to attach to
*/
public Fastpath(BaseConnection conn)
{
this.connection = conn;
this.executor = conn.getQueryExecutor();
}
/**
* 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
{
// Turn fastpath array into a parameter list.
ParameterList params = executor.createFastpathParameters(args.length);
for (int i = 0; i < args.length; ++i)
{
args[i].populateParameter(params, i + 1);
}
// Run it.
byte[] returnValue = executor.fastpathCall(fnId, params, connection.getAutoCommit());
// Interpret results.
if (!resultType || returnValue == null)
return returnValue;
if (returnValue.length != 4)
throw new PSQLException(GT.tr("Fastpath call {0} - No result was returned and we expected an integer.", new Integer(fnId)),
PSQLState.NO_DATA);
return new Integer((returnValue[3] & 255) |
((returnValue[2] & 255) << 8) |
((returnValue[1] & 255) << 16) |
((returnValue[0] & 255) << 24));
}
/**
* Send a function call to the PostgreSQL backend by name.
*
* Note: the mapping for the procedure name to function id needs to exist,
* usually to an earlier call to addfunction().
*
* This is the prefered method to call, as function id's can/may change
* between versions of the backend.
*
* For an example of how this works, refer to org.postgresql.largeobject.LargeObject
*
* @param name Function name
* @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 name is unknown or if a database-access error
* occurs.
* @see org.postgresql.largeobject.LargeObject
*/
public Object fastpath(String name, boolean resulttype, FastpathArg[] args) throws SQLException
{
if (connection.getLogger().logDebug())
connection.getLogger().debug("Fastpath: calling " + name);
return fastpath(getID(name), resulttype, args);
}
/**
* This convenience method assumes that the return value is an Integer
* @param name Function name
* @param args Function arguments
* @return integer result
* @exception SQLException if a database-access error occurs or no result
*/
public int getInteger(String name, FastpathArg[] args) throws SQLException
{
Integer i = (Integer)fastpath(name, true, args);
if (i == null)
throw new PSQLException(GT.tr("Fastpath call {0} - No result was returned and we expected an integer.", name),
PSQLState.NO_DATA);
return i.intValue();
}
/**
* This convenience method assumes that the return value is an oid.
* @param name Function name
* @param args Function arguments
* @exception SQLException if a database-access error occurs or no result
*/
public long getOID(String name, FastpathArg[] args) throws SQLException
{
long oid = getInteger(name, args);
if (oid < 0)
oid += NUM_OIDS;
return oid;
}
/**
* This convenience method assumes that the return value is not an Integer
* @param name Function name
* @param args Function arguments
* @return byte[] array containing result
* @exception SQLException if a database-access error occurs or no result
*/
public byte[] getData(String name, FastpathArg[] args) throws SQLException
{
return (byte[])fastpath(name, false, args);
}
/**
* This adds a function to our lookup table.
*
*
User code should use the addFunctions method, which is based upon a
* query, rather than hard coding the oid. The oid for a function is not
* guaranteed to remain static, even on different servers of the same
* version.
*
* @param name Function name
* @param fnid Function id
*/
public void addFunction(String name, int fnid)
{
func.put(name, new Integer(fnid));
}
/**
* This takes a ResultSet containing two columns. Column 1 contains the
* function name, Column 2 the oid.
*
*
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 org.postgresql.largeobject.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 org.postgresql.largeobject.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(GT.tr("The fastpath function {0} is unknown.", name), PSQLState.UNEXPECTED_ERROR);
return id.intValue();
}
/**
* Creates a FastpathArg with an oid parameter.
* This is here instead of a constructor of FastpathArg
* because the constructor can't tell the difference between
* an long that's really int8 and a long thats an oid.
*/
public static FastpathArg createOIDArg(long oid)
{
if (oid > Integer.MAX_VALUE)
oid -= NUM_OIDS;
return new FastpathArg((int)oid);
}
}