Skip site navigation (1) Skip section navigation (2)

Re: [PATCHES] Attempt to clean up ExecSql() in JDBC

From: Barry Lind <barry(at)xythos(dot)com>
To: Anders Bengtsson <ndrsbngtssn(at)yahoo(dot)se>
Cc: pgsql-patches(at)postgresql(dot)org, pgsql-jdbc(at)postgresql(dot)org
Subject: Re: [PATCHES] Attempt to clean up ExecSql() in JDBC
Date: 2001-08-28 05:48:33
Message-ID: 3B8B30B1.40008@xythos.com (view raw or flat)
Thread:
Lists: pgsql-jdbcpgsql-patches
I looked at the patch and it looks fine.  As for what fqp and hfr stand 
for I don't have a clue.  I was looking through the fe/be protocol 
documentation and think I might have a clue about what they are being 
used for.

thanks,
--Barry

Anders Bengtsson wrote:
> Hi,
> 
> Attached is my attempt to clean up the horrors of the ExecSQL() method in
> the JDBC driver.
> 
> I've done this by extracting it into a new method object called
> QueryExecutor (should go into org/postgresql/core/) and then taking it
> apart into different methods in that class.
> 
> A short summary:
> 
> * Extracted ExecSQL() from Connection into a method object called
>   QueryExecutor.
> 
> * Moved ReceiveFields() from Connection to QueryExecutor.
> 
> * Extracted parts of the original ExecSQL() method body into smaller
>   methods on QueryExecutor.
> 
> * Bug fix: The instance variable "pid" in Connection was used in two
>   places with different meaning. Both were probably in dead code, but it's
>   fixed anyway.
> 
> /Anders
> 
> 
> PS.: If anyone has any idea what the variable names "fqp" and "hfr" stand
> for, please tell me! :)
> 
> _____________________________________________________________________
> A n d e r s  B e n g t s s o n                   ndrsbngtssn(at)yahoo(dot)se
> Stockholm, Sweden
> 
> 
> ------------------------------------------------------------------------
> 
> Index: src/interfaces/jdbc/org/postgresql/Connection.java
> ===================================================================
> RCS file: /home/projects/pgsql/cvsroot/pgsql/src/interfaces/jdbc/org/postgresql/Connection.java,v
> retrieving revision 1.26
> diff -c -r1.26 Connection.java
> *** src/interfaces/jdbc/org/postgresql/Connection.java	2001/08/24 16:50:12	1.26
> --- src/interfaces/jdbc/org/postgresql/Connection.java	2001/08/26 18:33:48
> ***************
> *** 8,14 ****
>   import org.postgresql.fastpath.*;
>   import org.postgresql.largeobject.*;
>   import org.postgresql.util.*;
> ! import org.postgresql.core.Encoding;
>   
>   /**
>    * $Id: Connection.java,v 1.26 2001/08/24 16:50:12 momjian Exp $
> --- 8,14 ----
>   import org.postgresql.fastpath.*;
>   import org.postgresql.largeobject.*;
>   import org.postgresql.util.*;
> ! import org.postgresql.core.*;
>   
>   /**
>    * $Id: Connection.java,v 1.26 2001/08/24 16:50:12 momjian Exp $
> ***************
> *** 348,513 ****
>        * @return a ResultSet holding the results
>        * @exception SQLException if a database error occurs
>        */
> !     public java.sql.ResultSet ExecSQL(String sql,java.sql.Statement stat) throws SQLException
>       {
> !       // added Jan 30 2001 to correct maxrows per statement
> !       int maxrows=0;
> !       if(stat!=null)
> !         maxrows=stat.getMaxRows();
> ! 
> ! 	// added Oct 7 1998 to give us thread safety.
> ! 	synchronized(pg_stream) {
> !  	    // Deallocate all resources in the stream associated
> !   	    // with a previous request.
> !   	    // This will let the driver reuse byte arrays that has already
> !   	    // been allocated instead of allocating new ones in order
> !   	    // to gain performance improvements.
> !   	    // PM 17/01/01: Commented out due to race bug. See comments in
> !             // PG_Stream
> !             //pg_stream.deallocate();
> ! 
> ! 	    Field[] fields = null;
> ! 	    Vector tuples = new Vector();
> ! 	    byte[] buf = null;
> ! 	    int fqp = 0;
> ! 	    boolean hfr = false;
> ! 	    String recv_status = null, msg;
> ! 	    int update_count = 1;
> ! 	    int insert_oid = 0;
> ! 	    SQLException final_error = null;
> ! 
> ! 	    buf = encoding.encode(sql);
> ! 	    try
> ! 		{
> ! 		    pg_stream.SendChar('Q');
> ! 		    pg_stream.Send(buf);
> ! 		    pg_stream.SendChar(0);
> ! 		    pg_stream.flush();
> ! 		} catch (IOException e) {
> ! 		    throw new PSQLException("postgresql.con.ioerror",e);
> ! 		}
> ! 
> ! 	    while (!hfr || fqp > 0)
> ! 		{
> ! 		    Object tup=null;	// holds rows as they are recieved
> ! 
> ! 		    int c = pg_stream.ReceiveChar();
> ! 
> ! 		    switch (c)
> ! 			{
> ! 			case 'A':	// Asynchronous Notify
> ! 			    pid = pg_stream.ReceiveInteger(4);
> !                             msg = pg_stream.ReceiveString(encoding);
> ! 			    break;
> ! 			case 'B':	// Binary Data Transfer
> ! 			    if (fields == null)
> ! 				throw new PSQLException("postgresql.con.tuple");
> ! 			    tup = pg_stream.ReceiveTuple(fields.length, true);
> ! 			    // This implements Statement.setMaxRows()
> ! 			    if(maxrows==0 || tuples.size()<maxrows)
> ! 				tuples.addElement(tup);
> ! 			    break;
> ! 			case 'C':	// Command Status
> !                             recv_status = pg_stream.ReceiveString(encoding);
> ! 
> ! 				// Now handle the update count correctly.
> ! 				if(recv_status.startsWith("INSERT") || recv_status.startsWith("UPDATE") || recv_status.startsWith("DELETE") || recv_status.startsWith("MOVE")) {
> ! 					try {
> ! 						update_count = Integer.parseInt(recv_status.substring(1+recv_status.lastIndexOf(' ')));
> ! 					} catch(NumberFormatException nfe) {
> ! 						throw new PSQLException("postgresql.con.fathom",recv_status);
> ! 					}
> ! 					if(recv_status.startsWith("INSERT")) {
> ! 					    try {
> ! 						insert_oid = Integer.parseInt(recv_status.substring(1+recv_status.indexOf(' '),recv_status.lastIndexOf(' ')));
> ! 					    } catch(NumberFormatException nfe) {
> ! 						throw new PSQLException("postgresql.con.fathom",recv_status);
> ! 					    }
> ! 					}
> ! 				}
> ! 			    if (fields != null)
> ! 				hfr = true;
> ! 			    else
> ! 				{
> ! 				    try
> ! 					{
> ! 					    pg_stream.SendChar('Q');
> ! 					    pg_stream.SendChar(' ');
> ! 					    pg_stream.SendChar(0);
> ! 					    pg_stream.flush();
> ! 					} catch (IOException e) {
> ! 					    throw new PSQLException("postgresql.con.ioerror",e);
> ! 					}
> ! 				    fqp++;
> ! 				}
> ! 			    break;
> ! 			case 'D':	// Text Data Transfer
> ! 			    if (fields == null)
> ! 				throw new PSQLException("postgresql.con.tuple");
> ! 			    tup = pg_stream.ReceiveTuple(fields.length, false);
> ! 			    // This implements Statement.setMaxRows()
> ! 			    if(maxrows==0 || tuples.size()<maxrows)
> ! 				tuples.addElement(tup);
> ! 			    break;
> ! 			case 'E':	// Error Message
> !                             msg = pg_stream.ReceiveString(encoding);
> ! 			    final_error = new SQLException(msg);
> ! 			    hfr = true;
> ! 			    break;
> ! 			case 'I':	// Empty Query
> ! 			    int t = pg_stream.ReceiveChar();
> ! 
> ! 			    if (t != 0)
> ! 				throw new PSQLException("postgresql.con.garbled");
> ! 			    if (fqp > 0)
> ! 				fqp--;
> ! 			    if (fqp == 0)
> ! 				hfr = true;
> ! 			    break;
> ! 			case 'N':	// Error Notification
> !                             addWarning(pg_stream.ReceiveString(encoding));
> ! 			    break;
> ! 			case 'P':	// Portal Name
> !                             String pname = pg_stream.ReceiveString(encoding);
> ! 			    break;
> ! 			case 'T':	// MetaData Field Description
> ! 			    if (fields != null)
> ! 				throw new PSQLException("postgresql.con.multres");
> ! 			    fields = ReceiveFields();
> ! 			    break;
> ! 			case 'Z':       // backend ready for query, ignore for now :-)
> ! 			    break;
> ! 			default:
> ! 			    throw new PSQLException("postgresql.con.type",new Character((char)c));
> ! 			}
> ! 		}
> ! 	    if (final_error != null)
> ! 		throw final_error;
> ! 
> ! 	    return getResultSet(this, stat, fields, tuples, recv_status, update_count, insert_oid);
> ! 	}
> !     }
> ! 
> !     /**
> !      * Receive the field descriptions from the back end
> !      *
> !      * @return an array of the Field object describing the fields
> !      * @exception SQLException if a database error occurs
> !      */
> !     private Field[] ReceiveFields() throws SQLException
> !     {
> ! 	int nf = pg_stream.ReceiveIntegerR(2), i;
> ! 	Field[] fields = new Field[nf];
> ! 
> ! 	for (i = 0 ; i < nf ; ++i)
> ! 	    {
> !                 String typname = pg_stream.ReceiveString(encoding);
> ! 		int typid = pg_stream.ReceiveIntegerR(4);
> ! 		int typlen = pg_stream.ReceiveIntegerR(2);
> ! 		int typmod = pg_stream.ReceiveIntegerR(4);
> ! 		fields[i] = new Field(this, typname, typid, typlen, typmod);
> ! 	    }
> ! 	return fields;
>       }
>   
>       /**
> --- 348,356 ----
>        * @return a ResultSet holding the results
>        * @exception SQLException if a database error occurs
>        */
> !     public java.sql.ResultSet ExecSQL(String sql, java.sql.Statement stat) throws SQLException
>       {
> ! 	return new QueryExecutor(sql, stat, pg_stream, this).execute();
>       }
>   
>       /**
> ***************
> *** 793,799 ****
>        * This returns a resultset. It must be overridden, so that the correct
>        * version (from jdbc1 or jdbc2) are returned.
>        */
> !     protected abstract java.sql.ResultSet getResultSet(org.postgresql.Connection conn,java.sql.Statement stat, Field[] fields, Vector tuples, String status, int updateCount,int insertOID) throws SQLException;
>   
>       /**
>        * In some cases, it is desirable to immediately release a Connection's
> --- 636,642 ----
>        * This returns a resultset. It must be overridden, so that the correct
>        * version (from jdbc1 or jdbc2) are returned.
>        */
> !     public abstract java.sql.ResultSet getResultSet(org.postgresql.Connection conn,java.sql.Statement stat, Field[] fields, Vector tuples, String status, int updateCount,int insertOID) throws SQLException;
>   
>       /**
>        * In some cases, it is desirable to immediately release a Connection's
> Index: src/interfaces/jdbc/org/postgresql/jdbc1/Connection.java
> ===================================================================
> RCS file: /home/projects/pgsql/cvsroot/pgsql/src/interfaces/jdbc/org/postgresql/jdbc1/Connection.java,v
> retrieving revision 1.8
> diff -c -r1.8 Connection.java
> *** src/interfaces/jdbc/org/postgresql/jdbc1/Connection.java	2001/08/24 16:50:15	1.8
> --- src/interfaces/jdbc/org/postgresql/jdbc1/Connection.java	2001/08/26 18:33:48
> ***************
> *** 131,137 ****
>        * This overides the method in org.postgresql.Connection and returns a
>        * ResultSet.
>        */
> !     protected java.sql.ResultSet getResultSet(org.postgresql.Connection conn,java.sql.Statement stat, Field[] fields, Vector tuples, String status, int updateCount,int insertOID) throws SQLException
>       {
>         // in jdbc1 stat is ignored.
>   	return new org.postgresql.jdbc1.ResultSet((org.postgresql.jdbc1.Connection)conn,fields,tuples,status,updateCount,insertOID);
> --- 131,137 ----
>        * This overides the method in org.postgresql.Connection and returns a
>        * ResultSet.
>        */
> !     public java.sql.ResultSet getResultSet(org.postgresql.Connection conn,java.sql.Statement stat, Field[] fields, Vector tuples, String status, int updateCount,int insertOID) throws SQLException
>       {
>         // in jdbc1 stat is ignored.
>   	return new org.postgresql.jdbc1.ResultSet((org.postgresql.jdbc1.Connection)conn,fields,tuples,status,updateCount,insertOID);
> Index: src/interfaces/jdbc/org/postgresql/jdbc2/Connection.java
> ===================================================================
> RCS file: /home/projects/pgsql/cvsroot/pgsql/src/interfaces/jdbc/org/postgresql/jdbc2/Connection.java,v
> retrieving revision 1.10
> diff -c -r1.10 Connection.java
> *** src/interfaces/jdbc/org/postgresql/jdbc2/Connection.java	2001/08/24 16:50:16	1.10
> --- src/interfaces/jdbc/org/postgresql/jdbc2/Connection.java	2001/08/26 18:33:49
> ***************
> *** 204,210 ****
>        * This overides the method in org.postgresql.Connection and returns a
>        * ResultSet.
>        */
> !     protected java.sql.ResultSet getResultSet(org.postgresql.Connection conn, java.sql.Statement stat,Field[] fields, Vector tuples, String status, int updateCount, int insertOID) throws SQLException
>       {
>         // In 7.1 we now test concurrency to see which class to return. If we are not working with a
>         // Statement then default to a normal ResultSet object.
> --- 204,210 ----
>        * This overides the method in org.postgresql.Connection and returns a
>        * ResultSet.
>        */
> !     public java.sql.ResultSet getResultSet(org.postgresql.Connection conn, java.sql.Statement stat,Field[] fields, Vector tuples, String status, int updateCount, int insertOID) throws SQLException
>       {
>         // In 7.1 we now test concurrency to see which class to return. If we are not working with a
>         // Statement then default to a normal ResultSet object.
> 
> 
> ------------------------------------------------------------------------
> 
> 
> package org.postgresql.core;
> 
> import java.util.Vector;
> import java.io.IOException;
> import java.sql.*;
> import org.postgresql.*;
> import org.postgresql.util.PSQLException;
> 
> /**
>  * Executes a query on the backend.
>  *
>  * <p>The lifetime of a QueryExecutor object is from sending the query
>  * until the response has been received from the backend.
>  *
>  * $Id$
>  */
> 
> public class QueryExecutor {
> 
>     private final String sql;
>     private final java.sql.Statement statement;
>     private final PG_Stream pg_stream;
>     private final org.postgresql.Connection connection;
> 
>     public QueryExecutor(String sql,
> 			 java.sql.Statement statement,
> 			 PG_Stream pg_stream,
> 			 org.postgresql.Connection connection)
> 	throws SQLException
>     {
> 	this.sql = sql;
> 	this.statement = statement;
> 	this.pg_stream = pg_stream;
> 	this.connection = connection;
> 
> 	if (statement != null)
> 	    maxRows = statement.getMaxRows();
> 	else
> 	    maxRows = 0;
>     }
> 
>     private Field[] fields = null;
>     private Vector tuples = new Vector();
>     private String status = null;
>     private int update_count = 1;
>     private int insert_oid = 0;
>     private int maxRows;
> 
>     /**
>      * Execute a query on the backend.
>      */
>     public java.sql.ResultSet execute() throws SQLException {
> 
> 	int fqp = 0;
> 	boolean hfr = false;
> 
> 	synchronized(pg_stream) {
> 
> 	    sendQuery(sql);
> 
> 	    while (!hfr || fqp > 0) {
> 		int c = pg_stream.ReceiveChar();
> 
> 		switch (c)
> 		    {
> 		    case 'A':	// Asynchronous Notify
> 			int pid = pg_stream.ReceiveInteger(4);
> 			String msg = pg_stream.ReceiveString(connection.getEncoding());
> 			break;
> 		    case 'B':	// Binary Data Transfer
> 			receiveTuple(true);
> 			break;
> 		    case 'C':	// Command Status
> 			receiveCommandStatus();
> 
> 			if (fields != null)
> 			    hfr = true;
> 			else {
> 			    sendQuery(" ");
> 			    fqp++;
> 			}
> 			break;
> 		    case 'D':	// Text Data Transfer
> 			receiveTuple(false);
> 			break;
> 		    case 'E':	// Error Message
> 		        throw new SQLException(pg_stream.ReceiveString(connection.getEncoding()));
> 		    case 'I':	// Empty Query
> 			int t = pg_stream.ReceiveChar();
> 			if (t != 0)
> 			    throw new PSQLException("postgresql.con.garbled");
> 
> 			if (fqp > 0)
> 			    fqp--;
> 			if (fqp == 0)
> 			    hfr = true;
> 			break;
> 		    case 'N':	// Error Notification
> 			connection.addWarning(pg_stream.ReceiveString(connection.getEncoding()));
> 			break;
> 		    case 'P':	// Portal Name
> 			String pname = pg_stream.ReceiveString(connection.getEncoding());
> 			break;
> 		    case 'T':	// MetaData Field Description
> 			receiveFields();
> 			break;
> 		    case 'Z':       // backend ready for query, ignore for now :-)
> 			break;
> 		    default:
> 			throw new PSQLException("postgresql.con.type",
> 						new Character((char) c));
> 		    }
> 	    }
> 
> 	    return connection.getResultSet(connection, statement, fields, tuples, status, update_count, insert_oid);
> 	}
>     }
> 
>     /**
>      * Send a query to the backend.
>      */
>     private void sendQuery(String query) throws SQLException {
> 	try {
> 	    pg_stream.SendChar('Q');
> 	    pg_stream.Send(connection.getEncoding().encode(query));
> 	    pg_stream.SendChar(0);
> 	    pg_stream.flush();
> 
> 	} catch (IOException e) {
> 	    throw new PSQLException("postgresql.con.ioerror", e);
> 	}
>     }
> 
>     /**
>      * Receive a tuple from the backend.
>      *
>      * @param isBinary set if the tuple should be treated as binary data
>      */
>     private void receiveTuple(boolean isBinary) throws SQLException {
> 	if (fields == null)
> 	    throw new PSQLException("postgresql.con.tuple");
> 	Object tuple = pg_stream.ReceiveTuple(fields.length, isBinary);
> 	if (maxRows == 0 || tuples.size() < maxRows)
> 	    tuples.addElement(tuple);
>     }
> 
>     /**
>      * Receive command status from the backend.
>      */
>     private void receiveCommandStatus() throws SQLException {
> 
> 	status = pg_stream.ReceiveString(connection.getEncoding());
> 
> 	try {
> 	    // Now handle the update count correctly.
> 	    if (status.startsWith("INSERT") || status.startsWith("UPDATE") || status.startsWith("DELETE") || status.startsWith("MOVE")) {
> 		update_count = Integer.parseInt(status.substring(1 + status.lastIndexOf(' ')));
> 	    }
> 	    if (status.startsWith("INSERT")) {
> 		insert_oid = Integer.parseInt(status.substring(1 + status.indexOf(' '),
> 							       status.lastIndexOf(' ')));
> 	    }
> 	} catch (NumberFormatException nfe) {
> 	    throw new PSQLException("postgresql.con.fathom", status);
> 	}
>     }
> 
>     /**
>      * Receive the field descriptions from the back end.
>      */
>     private void receiveFields() throws SQLException {
> 	if (fields != null)
> 	    throw new PSQLException("postgresql.con.multres");
> 
> 	int size = pg_stream.ReceiveIntegerR(2);
> 	fields = new Field[size];
> 
> 	for (int i = 0; i < fields.length; i++) {
> 	    String typeName = pg_stream.ReceiveString(connection.getEncoding());
> 	    int typeOid = pg_stream.ReceiveIntegerR(4);
> 	    int typeLength = pg_stream.ReceiveIntegerR(2);
> 	    int typeModifier = pg_stream.ReceiveIntegerR(4);
> 	    fields[i] = new Field(connection, typeName, typeOid, typeLength, typeModifier);
> 	}
>     }
> }
> 
> 
> ------------------------------------------------------------------------
> 
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 2: you can get off all lists at once with the unregister command
>     (send "unregister YourEmailAddressHere" to majordomo(at)postgresql(dot)org)
> 
> execsql.patch
> 
> Content-Type:
> 
> TEXT/PLAIN
> Content-Encoding:
> 
> BASE64
> 
> 
> ------------------------------------------------------------------------
> QueryExecutor.java
> 
> Content-Type:
> 
> TEXT/PLAIN
> Content-Encoding:
> 
> BASE64
> 
> 
> ------------------------------------------------------------------------
> Part 1.4
> 
> Content-Type:
> 
> text/plain
> Content-Encoding:
> 
> binary
> 
> 



In response to

pgsql-patches by date

Next:From: Joerg HessdoerferDate: 2001-08-28 09:07:32
Subject: Bytea/Base64 encoders for libpq - interested?
Previous:From: Martijn van OosterhoutDate: 2001-08-28 02:15:05
Subject: Re: [PATCH] Prevent pg_dump running out of memory

pgsql-jdbc by date

Next:From: Barry LindDate: 2001-08-28 05:57:13
Subject: Re: Re: Proposal to fix Statement.executeBatch()
Previous:From: Rene PijlmanDate: 2001-08-27 22:40:27
Subject: Re: Re: Proposal to fix Statement.executeBatch()

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group