[HACKERS] Proposed patch for ODBC driver w/ C-a-n-c-e-l

    From: Bradley McLean <brad@bradm.net>

Patch against 7,2 submitted for comment.

This seems to work just fine; Now, when our users submit a 2 hour
query with four million row sorts by accident, then cancel it 30 seconds
later, it doesn't bog down the server ...

Author: Hiroshi Inoue

src/interfaces/odbc/connection.c

@@ -19,6 +19,9 @@
 #include <stdio.h>
 #include <string.h>
 #include <ctype.h>
+#ifndef	WIN32
+#include <errno.h>
+#endif /* WIN32 */
 
 #include "environ.h"
 #include "socket.h"
@@ -289,6 +292,7 @@ CC_Constructor()
 		rv->ms_jet = 0;
 		rv->unicode = 0;
 		rv->result_uncommitted = 0;
+		rv->schema_support = 0;
 #ifdef	MULTIBYTE
 		rv->client_encoding = NULL;
 		rv->server_encoding = NULL;
@@ -882,8 +886,8 @@ CC_connect(ConnectionClass *self, char do_password)
 					}
 					break;
 				case 'K':		/* Secret key (6.4 protocol) */
-					(void) SOCK_get_int(sock, 4);		/* pid */
-					(void) SOCK_get_int(sock, 4);		/* key */
+					self->be_pid = SOCK_get_int(sock, 4);		/* pid */
+					self->be_key = SOCK_get_int(sock, 4);		/* key */
 
 					break;
 				case 'Z':		/* Backend is ready for new query (6.4) */
@@ -1960,6 +1964,8 @@ CC_lookup_pg_version(ConnectionClass *self)
 		self->pg_version_minor = minor;
 	}
 	self->pg_version_number = (float) atof(szVersion);
+	if (PG_VERSION_GE(self, 7.3))
+		self->schema_support = 1;
 
 	mylog("Got the PostgreSQL version string: '%s'\n", self->pg_version);
 	mylog("Extracted PostgreSQL version number: '%1.1f'\n", self->pg_version_number);
@@ -2019,3 +2025,64 @@ CC_get_max_query_len(const ConnectionClass *conn)
 		value = BLCKSZ;
 	return value;
 }
+
+int
+CC_send_cancel_request(const ConnectionClass *conn)
+{
+#ifdef WIN32
+	int			save_errno = (WSAGetLastError());
+#else
+	int			save_errno = errno;
+#endif
+	int			tmpsock = -1;
+	struct
+	{
+		uint32		packetlen;
+		CancelRequestPacket cp;
+	}			crp;
+
+	/* Check we have an open connection */
+	if (!conn)
+		return FALSE;
+
+	if (conn->sock == NULL )
+	{
+		return FALSE;
+	}
+
+	/*
+	 * We need to open a temporary connection to the postmaster. Use the
+	 * information saved by connectDB to do this with only kernel calls.
+	*/
+	if ((tmpsock = socket(AF_INET, SOCK_STREAM, 0)) < 0)
+	{
+		return FALSE;
+	}
+	if (connect(tmpsock, (struct sockaddr *)&(conn->sock->sadr),
+				sizeof(conn->sock->sadr)) < 0)
+	{
+		return FALSE;
+	}
+
+	/*
+	 * We needn't set nonblocking I/O or NODELAY options here.
+	 */
+	crp.packetlen = htonl((uint32) sizeof(crp));
+	crp.cp.cancelRequestCode = (MsgType) htonl(CANCEL_REQUEST_CODE);
+	crp.cp.backendPID = htonl(conn->be_pid);
+	crp.cp.cancelAuthCode = htonl(conn->be_key);
+
+	if (send(tmpsock, (char *) &crp, sizeof(crp), 0) != (int) sizeof(crp))
+	{
+		return FALSE;
+	}
+
+	/* Sent it, done */
+	closesocket(tmpsock);
+#ifdef WIN32
+	WSASetLastError(save_errno);
+#else
+	errno = save_errno;
+#endif
+	return TRUE;
+}

src/interfaces/odbc/connection.h

@@ -126,6 +126,21 @@ typedef struct _StartupPacket6_2
 	char		tty[PATH_SIZE];
 } StartupPacket6_2;
 
+/* Transferred from pqcomm.h:  */
+
+
+typedef ProtocolVersion MsgType;
+
+#define PG_PROTOCOL(m,n)   (((m) << 16) | (n))
+#define CANCEL_REQUEST_CODE PG_PROTOCOL(1234,5678)
+
+typedef struct CancelRequestPacket
+{
+	/* Note that each field is stored in network byte order! */
+	MsgType		cancelRequestCode;	/* code to identify a cancel request */
+	unsigned int	backendPID;	/* PID of client's backend */
+	unsigned int	cancelAuthCode; /* secret key to authorize cancel */
+} CancelRequestPacket;
 
 /*	Structure to hold all the connection attributes for a specific
 	connection (used for both registry and file, DSN and DRIVER)
@@ -273,11 +288,14 @@ struct ConnectionClass_
 	char		ms_jet;
 	char		unicode;
 	char		result_uncommitted;
+	char		schema_support;
 #ifdef	MULTIBYTE
 	char	   *client_encoding;
 	char	   *server_encoding;
 #endif   /* MULTIBYTE */
 	int	ccsc;
+	int		be_pid;	/* pid returned by backend */
+	int		be_key; /* auth code needed to send cancel */
 };
 
 
@@ -319,6 +337,7 @@ void		CC_lookup_pg_version(ConnectionClass *conn);
 void		CC_initialize_pg_version(ConnectionClass *conn);
 void		CC_log_error(const char *func, const char *desc, const ConnectionClass *self);
 int			CC_get_max_query_len(const ConnectionClass *self);
+int		CC_send_cancel_request(const ConnectionClass *conn);
 void		CC_on_commit(ConnectionClass *conn);
 void		CC_on_abort(ConnectionClass *conn, BOOL set_no_trans);
 void		ProcessRollback(ConnectionClass *conn, BOOL undo);

src/interfaces/odbc/descriptor.h

@@ -5,7 +5,7 @@
  *
  * Comments:		See "notice.txt" for copyright and license information.
  *
- * $Id: descriptor.h,v 1.2 2002/04/01 03:01:14 inoue Exp $
+ * $Id: descriptor.h,v 1.3 2002/04/02 10:50:44 inoue Exp $
  *
  */
 
@@ -17,6 +17,7 @@
 typedef struct
 {
 	COL_INFO	*col_info; /* cached SQLColumns info for this table */
+	char		schema[MAX_TABLE_LEN + 1];
 	char		name[MAX_TABLE_LEN + 1];
 	char		alias[MAX_TABLE_LEN + 1];
 } TABLE_INFO;

src/interfaces/odbc/execute.c

@@ -573,6 +573,7 @@ PGAPI_Cancel(
 {
 	static char *func = "PGAPI_Cancel";
 	StatementClass *stmt = (StatementClass *) hstmt;
+	ConnectionClass *conn;
 	RETCODE		result;
 	ConnInfo   *ci;
 
@@ -589,14 +590,20 @@ PGAPI_Cancel(
 		SC_log_error(func, "", NULL);
 		return SQL_INVALID_HANDLE;
 	}
-	ci = &(SC_get_conn(stmt)->connInfo);
+	conn = SC_get_conn(stmt);
+	ci = &(conn->connInfo);
 
 	/*
 	 * Not in the middle of SQLParamData/SQLPutData so cancel like a
 	 * close.
 	 */
 	if (stmt->data_at_exec < 0)
 	{
+		/*
+		 * Tell the Backend that we're cancelling this request
+		 */
+		if (stmt->status == STMT_EXECUTING)
+			CC_send_cancel_request(conn);
 		/*
 		 * MAJOR HACK for Windows to reset the driver manager's cursor
 		 * state: Because of what seems like a bug in the Odbc driver