Attempt to clean up ExecSql() in JDBC

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@yahoo.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);
}
}
}

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execsql.patch

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QueryExecutor.java

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