Be paranoid.

[moira.git] / gdb / gdb_db.c

/*
 *	$Source$
 *	$Header$
 */

#ifndef lint
static char *rcsid_gdb_db_c = "$Header$";
#endif	lint

/************************************************************************/
/*	
/*				gdb_db.c
/*	
/*	Authors: Susan Ryan and Noah Mendelsohn
/*	
/*	Copyright: 1986 MIT Project Athena
/*	
/************************************************************************/

#include <stdio.h>
#include <strings.h>
#include "gdb.h"



\f/************************************************************************/
/*	
/*				start_accessing_db (start_accessing_db)
/*	
/*	1) Creates a new db structure to describe the database.
/*	
/*	2) Parses the supplied db_ident into a server and a db name
/*	
/*	3) Opens a connection to the server, sending the name of the 
/*	   database as an argument
/*	
/*	4) Asynchronously receives a return code from the server
/*	   to indicate whether the database could be accessed
/*	
/*	5) If successful, the handle on the new structure is placed into
/*	   the variable supplied by the caller.  Otherwise, the structure
/*	   is de_allocated and failure status is returned to the caller.
/*	
/*	Note: this code was adapted from an earlier synchronous 
/*	      implementation and there may yet be some loose ends.
/*	
/************************************************************************/

#define MIN_NAME_LEN 1   /*completely arbitrary */
#define FAILURE NULL /*until we decide what it should really be */
		     /*note if fails returns NULL for the db_handle value*/
		     /*as per above	*/

DATABASE g_make_db();
int g_iadb();

struct adb_data {
	DATABASE db;
	OPERATION get_retcode;
};

int
start_accessing_db (op, db_ident, db_handle)
OPERATION op;
char *db_ident;
DATABASE *db_handle;               
{
	/*----------------------------------------------------------*/
	/*	
	/*			Declarations
	/*	
	/*----------------------------------------------------------*/

	register DATABASE db;			/* the newly created */
						/* structure */
	register struct adb_data *arg;		/* holds our state */
						/* during async operation*/
	char *ident, *server, *temp_server;	/* loop variables for */
						/* parsing*/
	char *db_name, *temp_name;
	int count;				/* counts chars during parse */

	CONNECTION connexn;			/* the connection to the */
						/* database server*/

	/*----------------------------------------------------------*/
	/*	
	/*		    Execution begins here
	/*	
	/*	Make sure parameters are correct, then allocate a
	/*	structure.
	/*	
	/*----------------------------------------------------------*/

	GDB_INIT_CHECK

	db_name = NULL;
	temp_name = NULL;
	ident = NULL ;
	server = NULL;

	GDB_CHECK_OP(op, "start_accessing_db")

	if ((db_ident == NULL)|| (strlen(db_ident)<MIN_NAME_LEN)) {
		fprintf (gdb_log,"access_db: correct syntax is db_name@server \n");
		*db_handle = NULL;
		return (OP_CANCELLED);
	}

	db = g_make_db();
        *db_handle = db;

	/*----------------------------------------------------------*/
	/*	
	/*	Loop to count lengths of server and database names
	/*	Allocate space for each and copy them both
	/*	
	/*----------------------------------------------------------*/

	count = 1;
	ident = db_ident;
        while (*ident++ != '@') {
		count++;
	}

        db_name = db_alloc (count);		/* space for db_name */
        					/* note: this is cleaned */
						/* up by the tear down rtn*/

	count = 1;
        while (*ident++ != '\0') 
		count++;

	count += strlen(GDB_DB_SERVICE)+1;	/* leave room for :service */
        server = db_alloc (count);		/* space for host:service */
        					/* note: this is cleaned */
						/* up by the tear down rtn*/

       /*
        * copy head of db_ident string from db_name@server to db_name
        */
	temp_name = db_name;
	while (*db_ident != '@') {
		*temp_name = *db_ident;
		temp_name++;
		db_ident++;
	}
	*temp_name = '\0';

        db->name = db_name; 				 

       /*
        * Set up server host name
        */
	temp_server = server;	
	db_ident++;				/* skip the '@' */
        while (*db_ident!= '\0') {
		*temp_server = *db_ident;
		temp_server++;
		db_ident++; 	
	}

       /*
        * Append :service id to the server host name
        */
	*temp_server++ = ':';
	*temp_server = '\0';
	(void) strcat(server, GDB_DB_SERVICE);

	db->server = server;


	/*----------------------------------------------------------*/
	/*	
	/*	Create a connection to the server.
	/*	
	/*----------------------------------------------------------*/

	connexn = start_server_connection (server, db_name);

	if (connexn==NULL || connection_status(connexn) != CON_UP) {
	     connection_perror(connexn, "Error starting server connection");
	     fprintf (gdb_log, "gdb:access_db: couldn't connect to server %s \n", server);
	     g_tear_down(*db_handle);
	     OP_STATUS(op) = OP_CANCELLED;
	     return (OP_CANCELLED);
	}

        db->connection = connexn;

       /*
        * Start asynchronously receiving the return code from the 
        * data base server.  May take awhile, since ingres is so
        * slow to start up.
        */

	arg = (struct adb_data *)db_alloc(sizeof(struct adb_data));
	arg->get_retcode = create_operation();
	arg->db = db;

	start_receiving_object (arg->get_retcode, connexn, 
				(char *)&(OP_RESULT(op)), INTEGER_T);	
       /*
        * Error handling
        */
	if (OP_STATUS(arg->get_retcode) == OP_CANCELLED) {
	    g_tear_down (*db_handle);
	    OP_STATUS(op) = OP_CANCELLED;
	    delete_operation(arg->get_retcode);
	    db_free((char *)arg, sizeof(struct adb_data));
	    return OP_CANCELLED;
        }

       /*
        * We've successfully queued the receive of the return code.
        * That's about all we have to do if things go well, but if the
        * operation fails later, we have to be there to clean up.  To
        * get control back, we queue ourselves as a second operation
        * so we can see how the first did, and so we can free up arg.
        */
	initialize_operation(op, g_iadb, (char *)arg, (int (*)())NULL); 
	(void) queue_operation(connexn, CON_INPUT, op);

	return OP_RUNNING;		
}

	/*----------------------------------------------------------*/
	/*	
	/*			g_iadb
	/*	
	/*	Init routine for getting return code on accessing a
	/*	database.  If all went well, (or even if it didn't), then
	/*	we are done.  All we have to do is clean up the stuff we've
	/*	allocated.
	/*	
	/*----------------------------------------------------------*/

int
g_iadb(op, hcon, arg)
OPERATION op;
HALF_CONNECTION hcon;
struct adb_data *arg;
{
	int rc;

       /*
        * Figure out how the receipt went
        */
	rc = OP_STATUS(arg->get_retcode);

       /*
        * Release all transient data structures.
        */
	if (rc != OP_COMPLETE || op->result != DB_OPEN)
		g_tear_down(arg->db);
	else
	        DB_STATUS(arg->db) = DB_OPEN;
	  
	delete_operation(arg->get_retcode);
	db_free((char *)arg, sizeof(struct adb_data));
	
	return rc;
}
\f
/************************************************************************/
/*	
/*			g_tear_down
/*	
/*	this is called by access_db and perf_db_op when a fatal error 
/*	is reached. It is an attempt to intelligently handle the error,
/*	and tear down connections and data structures if necessary.
/*	
/*	The current version simply tears down everything, perhaps later
/*	versions should make provision for closing the db as necessary,
/*	and/or other less drastic ways to handle the errors.
/*	 
/************************************************************************/

int
g_tear_down (db_handle)
DATABASE db_handle;
{
	register DATABASE db = db_handle; 

	/*----------------------------------------------------------*/
	/*	
	/*	If the db is opened, and the connexn is severed, 
	/*	some error handling, closing of the db should be done 
	/*	at the server.
	/*	
	/*	Also, at the server, perhaps a return code to indicate
	/*	that user tried to open non-existant db???
	/*	
	/*----------------------------------------------------------*/
	  

	if (db==NULL)
	        return;


       	(void) sever_connection (db->connection);

       /*
        * Free up the separately allocated strings to which the
        * database descriptor points
        */
	gdb_fstring(db->server);
	gdb_fstring(db->name);

       /*
        * Free the descriptor itself
        */
	db_free ((char *)db,sizeof(struct db_struct));
	return;
}
\f
/************************************************************************/
/*	
/*			  g_make_db
/*	
/*	Allocate and initialize a database descriptor structure.
/*	
/************************************************************************/

DATABASE
g_make_db()
{
	register DATABASE db;

	db = (DATABASE)db_alloc (sizeof(struct db_struct));
	db->id = GDB_DB_ID;
	db->connection = NULL;
	db->name = NULL;
	db->server = NULL;
	DB_STATUS(db) = DB_CLOSED;
	
	return db;
}
\f/************************************************************************/
/*	
/*				access_db (access_db)
/*	
/*	Does a start_accessing_db and waits for it to complete.
/*	
/************************************************************************/

int
access_db (db_ident, db_handle)
char *db_ident;
DATABASE *db_handle;               
{
	register OPERATION op;
	register int status;
	register int result;

	GDB_INIT_CHECK

       /*
        * Create an operation and use it to asynchronously access
        * the database
        */
	op = create_operation();
	(void) start_accessing_db(op, db_ident, db_handle);

       /*
        * Wait for it to complete, note whether the operation completed
        * at all, and if so, whether it returned a successful result
        * in accessing the database.  Then reclaim the space used for
        * the operation.
        */
	(void) complete_operation(op);
	status = OP_STATUS(op);
	result = OP_RESULT(op);

	delete_operation(op);

       /*
        * Tell the caller either that we were interrupted, or pass
        * on the actual result of accessing the database.  If it
        * failed, then tear everything down after all.
        */
	if (status==OP_COMPLETE)
		return result;
	else
		return status;
}
\f/************************************************************************/
/*	
/*		  start_performing_db_operation (start_performing_db_operation)
/*	
/*	Asynchronously performs  any operation except for a query
/*	on the remote database.
/*	
/*	The operation is encoded as a GDB string and sent to the server.
/*	
/*	An integer return code is received back and returned to the caller.
/*	
/*	Note that this operation executes on both the outbound and inbound
/*	half connections.  Since there is no explicit sync between the two
/*	directions, operations like this pipeline freely from requestor
/*	to server, but there is no way to cancel this operation once it
/*	has started without severing the accompanying connection.
/*	
/************************************************************************/

int g_ipdb();

struct pdb_data {
	DATABASE db;				/* the database we're */
						/* working on */
	OPERATION send_request;			/* used to send the string */
						/* containing the db oper. */
						/* to be performed */
	OPERATION get_retcode;			/* used to get back the */
						/* response to our request */
	STRING s;				/* the operation string */
						/* itself.  This is sent. */
};

#define MIN_REQUEST_LEN 1 /*completely arbitrary */
#undef FAILURE
#define FAILURE -1

int
start_performing_db_operation (op, db_handle,request)
OPERATION op;
DATABASE db_handle; 
char *request;
{
	/*----------------------------------------------------------*/
	/*	
	/*			Declarations
	/*	
	/*----------------------------------------------------------*/

	register struct pdb_data *arg;		/* holds our state */
						/* during async operation*/
	register DATABASE db = db_handle;	/* fast working copy */

	/*----------------------------------------------------------*/
	/*	
	/*		    Execution begins here
	/*	
	/*	Make sure parameters are correct, then allocate a
	/*	structure.
	/*	
	/*----------------------------------------------------------*/

	GDB_CHECK_OP(op, "start_performing_db_operation ")
        if (db==NULL) {
		fprintf (gdb_log, "gdb: start_performing_db_operation: supplied database is NULL\n");
                OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
        }

	GDB_CHECK_DB(db, "start_performing_db_operation")

	if (DB_STATUS(db) != DB_OPEN) {
		fprintf (gdb_log, "gdb: start_performing_db_operation: request to closed database ");
		OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
	}

        if (db->connection == NULL) {
                fprintf (gdb_log,
			 "gdb: start_performing_db_operation: connection severed, request cancelled\n");
                OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
        }

        if (connection_status(db->connection) != CON_UP ) {
                fprintf (gdb_log, "gdb: start_performing_db_operation: problems maintaining connection ");
		connection_perror(db->connection, "Reason for connection failure");
		fprintf (gdb_log, "request cancelled \n");
                OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
        }

        if ((request == NULL) || (strlen (request)<MIN_REQUEST_LEN)) { 
                fprintf (gdb_log, "gdb: start_performing_db_operation: request either missing or too short\n");
                OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
                  /*should we disallow empty requests? */
        }


	/*----------------------------------------------------------*/
	/*	
	/*	Asynchronously send the request to the server
	/*	
	/*----------------------------------------------------------*/

       /*
        * Allocate a structure to hold our state while we're gone
        * waiting for this to complete.
        */

	arg = (struct pdb_data *)db_alloc(sizeof(struct pdb_data));
	arg->db = db;
	arg->send_request = create_operation();

       /*
        * Send the request string to the server
        */
	STRING_DATA(arg->s) = request;
	MAX_STRING_SIZE(arg->s) = strlen (request) +1;
	start_sending_object (arg->send_request, db->connection, 
				(char *)&(arg->s), STRING_T);	
	if (OP_STATUS(arg->send_request) == OP_CANCELLED) {
	    OP_STATUS(op) = OP_CANCELLED;
	    delete_operation(arg->send_request);
	    db_free((char *)arg, sizeof(struct pdb_data));
	    return OP_CANCELLED;
        }

	/*----------------------------------------------------------*/
	/*	
	/*	Asynchronously receive the return code (note, we
	/*	really don't know whether the request has even been
	/*	sent yet...doesn't really matter.)
	/*	
	/*----------------------------------------------------------*/

	arg->get_retcode = create_operation();
       /*
        *  This must come here as it sets op_result 
        */
	initialize_operation(op, g_ipdb, (char *)arg, (int (*)())NULL);

	start_receiving_object (arg->get_retcode, db->connection, 
				(char *)&(OP_RESULT(op)), INTEGER_T);	
	if (OP_STATUS(arg->get_retcode) == OP_CANCELLED) {
	    OP_STATUS(op) = OP_CANCELLED;
	    (void) cancel_operation(arg->send_request);/* this could be a bug, */
						/* because we introduce */
						/* indeterminism into */
						/* the reply stream, probably */
						/* should shutdown the whole */
						/* db here */
	    delete_operation(arg->send_request);
	    delete_operation(arg->get_retcode);
	    db_free((char *)arg, sizeof(struct adb_data));
	    return OP_CANCELLED;
        }

       /*
        * We've successfully queued the receive of the return code.
        * That's about all we have to do if things go well, but if the
        * operation fails later, we have to be there to clean up.  To
        * get control back, we queue ourselves as a second operation
        * so we can see how the first did, and so we can free up arg.
        */
	(void) queue_operation(db->connection, CON_INPUT, op);
	return OP_RUNNING;
}

	/*----------------------------------------------------------*/
	/*	
	/*			g_ipdb
	/*	
	/*	Init routine for getting return code on performin a db
	/*	operation.  If all went well, (or even if it didn't),
	/*	then we are done.  All we have to do is clean up the
	/*	stuff we've allocated.
	/*	
	/*----------------------------------------------------------*/

int
g_ipdb(op, hcon, arg)
OPERATION op;
HALF_CONNECTION hcon;
struct pdb_data *arg;
{
	int rc1, rc2;

       /*
        * Figure out how the receipt went
        */
	rc1 = OP_STATUS(arg->send_request);
	rc2 = OP_STATUS(arg->get_retcode);

       /*
        * Release all transient data structures.
        */
	if (rc1 != OP_COMPLETE || rc2 != OP_COMPLETE)
		g_tear_down(arg->db);
	  
	delete_operation(arg->send_request);
	delete_operation(arg->get_retcode);
	db_free((char *)arg, sizeof(struct pdb_data));
	
	return rc2;
}
\f
/************************************************************************/
/*	
/*			perform_db_operation (perform_db_operation)
/*	
/*	Do a database operation synchronously.  This just calls
/*	the async routine and waits for it to complete.
/*	
/************************************************************************/

perform_db_operation (db_handle,request)
DATABASE db_handle; 
char *request;
{
	register OPERATION op;
	register int status;
	register int result;

       /*
        * Create an operation and use it to asynchronously perform
        * the operation
        */
	op = create_operation();
	(void) start_performing_db_operation(op, db_handle, request);

       /* 
        * Wait for it to complete, note whether the operation
        * completed at all, and if so, whether it returned a
        * successful result.  Then reclaim the space used for the
        * operation.
        */
	(void) complete_operation(op);
	status = OP_STATUS(op);
	result = OP_RESULT(op);

	delete_operation(op);

       /*
        * Tell the caller either that we were interrupted, or pass
        * on the actual result of accessing the database.  If it
        * failed, then tear everything down after all.
        */
	if (status==OP_COMPLETE)
		return result;
	else
		return status;
}
\f/************************************************************************/
/*	
/*		  start_db_query (start_db_query)
/*	
/*	Asynchronously performs a database query on the remote
/*	database.
/*	
/*	The operation is encoded as a GDB string and sent to the server.
/*	
/*	An integer return code is received back and returned to the caller.
/*	
/*	If the return code indicates success, then we go into a loop
/*	receiving the retrieved data.  Each returned tuple is preceeded by
/*	a so-called yes/no flag, which indicates whether tuple data is really
/*	to follow.  Last tuple is followed by a NO flag.
/*	
/*	Note that this operation executes on both the outbound and inbound
/*	half connections.  Since there is no explicit sync between the two
/*	directions, operations like this pipeline freely from requestor
/*	to server, but there is no way to cancel this operation once it
/*	has started without severing the accompanying connection.
/*	
/************************************************************************/

int g_idbq();
int g_cdbq();

struct dbq_data {
       /*
        * Following may be used throughout processing
        */
	DATABASE db;				/* the database we're */
						/* working on */
	RELATION rel;
	TUPLE_DESCRIPTOR tpd;
       /*
        * used primarily in first phase for sending query and getting
        * return code
        */
	OPERATION send_query;			/* used to send the string */
						/* containing the query */
						/* to be performed */
	OPERATION send_descriptor;		/* used to send the tuple */
						/* descriptor to the server */
	OPERATION get_retcode;			/* used to get back the */
						/* response to our request */
	STRING s;				/* the operation string */
						/* itself.  This is sent. */
       /*
        * Following are used during later phase to receive the tuples 
        */
	int state;				/* are we expecting a yes/no */
						/* or a tuple next? */
#define YESNO 1
#define TUPDATA 2
	int yesno;				/* an indicator of whether */
						/* another tuple is to follow*/
#define YES 1
	OPERATION receive_yesno_or_data;
	TUPLE tup;				/* a place to put */
						/* the next tuple */
};

int
start_db_query (op, db_handle,rel, query)
OPERATION op;
DATABASE db_handle; 
RELATION rel;
char *query;
{
	/*----------------------------------------------------------*/
	/*	
	/*			Declarations
	/*	
	/*----------------------------------------------------------*/

	register struct dbq_data *arg;		/* holds our state */
						/* during async operation*/
	register DATABASE db = db_handle;	/* fast working copy */

	/*----------------------------------------------------------*/
	/*	
	/*		    Execution begins here
	/*	
	/*	Make sure parameters are correct, then allocate a
	/*	structure.
	/*	
	/*----------------------------------------------------------*/

	GDB_CHECK_OP(op, "start_db_query ")

        if (rel ==NULL) {
		fprintf (gdb_log, "gdb: query_db: input rel is null \n");
                OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
        }

        if (db==NULL) {
		fprintf (gdb_log, "gdb: start_db_query: supplied database is NULL\n");
                OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
        }

	GDB_CHECK_DB(db, "start_db_query")

	if (DB_STATUS(db) != DB_OPEN) {
		fprintf (gdb_log, "gdb: start_db_query: request to closed database ");
		OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
	}

        if (db->connection == NULL) {
                fprintf (gdb_log,"gdb: start_db_query: connection severed, request cancelled\n");
                OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
        }

        if (connection_status(db->connection) != CON_UP ) {
                fprintf (gdb_log,"gdb: start_db_query: problems maintaining connection ");
		connection_perror(db->connection, "Reason for connection failure");
		fprintf (gdb_log,"request cancelled \n");
                OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
        }

        if (query == NULL || *query == '\0') { 
                fprintf (gdb_log, "gdb: start_db_query: request string is null\n");
                OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
        }


	/*----------------------------------------------------------*/
	/*	
	/*	Asynchronously send the query to the server
	/*	
	/*----------------------------------------------------------*/

       /*
        * Allocate a structure to hold our state while we're gone
        * waiting for this to complete.
        */

	arg = (struct dbq_data *)db_alloc(sizeof(struct dbq_data));
	arg->db = db;
	arg->rel = rel;
	arg->send_query = create_operation();

       /*
        * Send the query string to the server
        */
	(void) string_alloc(&(arg->s), strlen(query)+11);
	(void) strcpy(STRING_DATA(arg->s), "retrieve ");
	(void) strcat(STRING_DATA(arg->s), query);
       	MAX_STRING_SIZE(arg->s) = strlen (query) +11;
	start_sending_object (arg->send_query, db->connection, 
				(char *)&(arg->s), STRING_T);	
	if (OP_STATUS(arg->send_query) == OP_CANCELLED) {
	    OP_STATUS(op) = OP_CANCELLED;
	    delete_operation(arg->send_query);
	    string_free(&(arg->s));
	    db_free((char *)arg, sizeof(struct dbq_data));
	    return OP_CANCELLED;
        }

       /*
        * Send the tuple descriptor to the server
        */

	arg->send_descriptor = create_operation();
	arg->tpd = DESCRIPTOR_FROM_RELATION(arg->rel);

	start_sending_object (arg->send_descriptor, db->connection, 
				(char *)&(arg->tpd), TUPLE_DESCRIPTOR_T);
	if (OP_STATUS(arg->send_descriptor) == OP_CANCELLED) {
	    OP_STATUS(op) = OP_CANCELLED;
	    (void) cancel_operation(arg->send_query);/* this could be a bug, */
						/* because we introduce */
						/* indeterminism into */
						/* the reply stream, probably */
						/* should shutdown the whole */
						/* db here */
	    delete_operation(arg->send_query);
	    delete_operation(arg->send_descriptor);
	    string_free(&(arg->s));
	    db_free((char *)arg, sizeof(struct dbq_data));
	    return OP_CANCELLED;
        }

	/*----------------------------------------------------------*/
	/*	
	/*	Asynchronously receive the return code (note, we
	/*	really don't know whether the query/and the descriptor
	/*	have even been sent yet...doesn't really matter.)
	/*	
	/*----------------------------------------------------------*/

	arg->get_retcode = create_operation();
	start_receiving_object (arg->get_retcode, db->connection, 
				(char *)&(OP_RESULT(op)), INTEGER_T);	
	if (OP_STATUS(arg->get_retcode) == OP_CANCELLED) {
	    OP_STATUS(op) = OP_CANCELLED;
	    (void) cancel_operation(arg->send_query);/* this could be a bug, */
						/* because we introduce */
						/* indeterminism into */
						/* the reply stream, probably */
						/* should shutdown the whole */
						/* db here */
	    (void) cancel_operation(arg->send_descriptor);
	    string_free(&(arg->s));
	    delete_operation(arg->send_query);
	    delete_operation(arg->send_descriptor);
	    delete_operation(arg->get_retcode);
	    db_free((char *)arg, sizeof(struct adb_data));
	    return OP_CANCELLED;
        }

       /*
        * We've successfully queued the receive of the return code.
        * That's about all we have to do if things go well, but if the
        * operation fails later, we have to be there to clean up.  To
        * get control back, we queue ourselves as a second operation
        * so we can see how the first did, and so we can free up arg.
        */
	initialize_operation(op, g_idbq, (char *)arg, (int (*)())NULL);
	(void) queue_operation(db->connection, CON_INPUT, op);

	return OP_RUNNING;
}

	/*----------------------------------------------------------*/
	/*	
	/*			g_idbq
	/*	
	/*	Init routine for getting return code on performing a
	/*	bd query.  If there was an error, then we are done except for
	/*	cleaning up all the dynamic memory we allocated.
	/*	If the return code was 0,then we must asynchronously
	/*	do the following iteratively until a no is received:
	/*	
	/*	  while (async_receive(yes/no) == yes) {
	/*	       async receive new tuple
	/*	       add it to the relation 
	/*	  } 
	/*	
	/*----------------------------------------------------------*/

int
g_idbq(op, hcon, arg)
OPERATION op;
HALF_CONNECTION hcon;
struct dbq_data *arg;
{
	int rc1, rc2, rc3;

	/*----------------------------------------------------------*/
	/*	
	/*	See how the three asynchronous operations went,and
	/*	clean up after them.
	/*	
	/*----------------------------------------------------------*/

       /*
        * Figure out how the receipt went
        */
	rc1 = OP_STATUS(arg->send_query);
	rc2 = OP_STATUS(arg->send_descriptor);
	rc3 = OP_STATUS(arg->get_retcode);

       /*
        * Release all transient data structures which were used in the
        * preliminary operations.
        */
	delete_operation(arg->send_query);
	delete_operation(arg->get_retcode);
	string_free(&(arg->s));
       /*
        * If we've failed for any reason, then mark ourselves complete and
        * return.
        */
	if (rc1 != OP_COMPLETE || rc2 != OP_COMPLETE|| rc3 != OP_COMPLETE
	    || OP_RESULT(op) != OP_SUCCESS) {
		    OP_STATUS(op) = rc3;	/* we must have done */
						/* about as well as */
						/* the last one */
		
		    db_free((char *)arg, sizeof(struct dbq_data));
		    return rc3;			/* tell the dispatcher */
						/* that we're either */
						/* cancelled or complete */
        }
	  
	/*----------------------------------------------------------*/
	/*	
	/*	We've successfully received a return code of 0 from
	/*	Ingres, which means we are now going to begin the
	/*	yes/no loop.
	/*	
	/*----------------------------------------------------------*/

	op->fcn.cont = g_cdbq;			/* after the preempting */
						/* receive completes, the */
						/* dispatcher will call */
						/* this routine. */
	arg->state = YESNO;			/* tell continuation routine */
						/* that we're receiving */
						/* a yes/no */
	arg->tup = NULL;			/* so we won't try to clean */
						/* it up */
	arg->receive_yesno_or_data = create_operation();
	
	preempt_and_start_receiving_object(arg->receive_yesno_or_data,
					   op,
					   (char *)&(arg->yesno),
					   INTEGER_T);
	return OP_PREEMPTED;	
}

	/*----------------------------------------------------------*/
	/*	
	/*			g_cdbq
	/*	
	/*	Continuation routine for receiving results of a query.
	/*	Tbis is called repeatedly each time either a yes/no or
	/*	a new tuple is received.  It repeatedly preempts itself
	/*	to receive the next yes/no or tuple until a 'no'
	/*	is finally received.
	/*	
	/*----------------------------------------------------------*/

int
g_cdbq(op, hcon, arg)
OPERATION op;
HALF_CONNECTION hcon;
struct dbq_data *arg;
{
	/*----------------------------------------------------------*/
	/*	
	/*	See whether the preempting operation completed
	/*	successfully.  If not, we just clean up and cancel
	/*	
	/*----------------------------------------------------------*/

	if (OP_STATUS(arg->receive_yesno_or_data) != OP_COMPLETE) {
		delete_operation(arg->receive_yesno_or_data);
		if (arg->tup != NULL)
			delete_tuple(arg->tup);
		db_free((char *)arg, sizeof(struct dbq_data));
		OP_STATUS(op) = OP_CANCELLED;
		return OP_CANCELLED;
	}

	/*----------------------------------------------------------*/
	/*	
	/*	Whatever it was, we received it cleanly.  If it 
	/*	was tuple data, then accept it and prepare to receive
	/*	a yesno.  If it was a yes, then prepare to receive
	/*	the tuple data.  If it was a NO, then we're all done.
	/*	
	/*	Note that g_cdbg will be recalled by the dispatcher
	/*	after the preempting routines have completed.
	/*	
	/*----------------------------------------------------------*/

       /*
        * New TUPLE DATA
        */

	if (arg->state == TUPDATA) {
		ADD_TUPLE_TO_RELATION(arg->rel, arg->tup);
		arg->tup = NULL;		/* so we won't try to */
						/* delete it in case of error*/
		reset_operation(arg->receive_yesno_or_data);
		arg->state = YESNO;
		preempt_and_start_receiving_object(arg->receive_yesno_or_data,
						   op,
						   (char *)&(arg->yesno),
						   INTEGER_T);
		return OP_PREEMPTED;	
	}

       /*
        * We just received a yes or no. If it's a YES, prepare to
        * receive some more tuple data.
        */
	if (arg->yesno == YES)  {
		arg->tup = create_tuple(arg->tpd);
		reset_operation(arg->receive_yesno_or_data);
		arg->state = TUPDATA;
		preempt_and_start_receiving_object(arg->receive_yesno_or_data,
						   op,
						   (char *)arg->tup,
						   TUPLE_DATA_T);
		return OP_PREEMPTED;	
	}
       /*
        * We just received a NO.  Looks like we're all done cleanly.
        */
	delete_operation(arg->receive_yesno_or_data);
	if (arg->tup != NULL)
		delete_tuple(arg->tup);
	db_free((char *)arg, sizeof(struct dbq_data));
	OP_STATUS(op) = OP_COMPLETE;
	return OP_COMPLETE;
	
}
\f
/************************************************************************/
/*	
/*				db_query (db_query)
/*	
/*	Perform a relational query on the specified database.
/*	
/*	This just calls the asynchronous form of doing a query and
/*	waits for it to complete.
/*	
/*	
/************************************************************************/

int
db_query(db_handle, rel, query)
DATABASE db_handle; 
RELATION rel;
char *query;
{
	register OPERATION op;
	register int status;
	register int result;

       /*
        * Create an operation and use it to asynchronously perform
        * the operation
        */
	op = create_operation();
	(void) start_db_query(op, db_handle, rel, query);

       /* 
        * Wait for it to complete, note whether the operation
        * completed at all, and if so, whether it returned a
        * successful result.  Then reclaim the space used for the
        * operation.
        */
	(void) complete_operation(op);
	status = OP_STATUS(op);
	result = OP_RESULT(op);

	delete_operation(op);

       /*
        * Tell the caller either that we were interrupted, or pass
        * on the actual result of accessing the database.  If it
        * failed, then tear everything down after all.
        */
	if (status==OP_COMPLETE)
		return result;
	else
		return status;
}