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Invent a new, more thread-safe version of PQrequestCancel, called PQcancel.

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Use this new function in psql.  Implement query cancellation in psql for
Windows.  Code by Magnus Hagander, documentation and minor editorialization
by Tom Lane.
This commit is contained in:
Tom Lane
2004-10-30 23:11:27 +00:00
parent 80559fa9e9
commit 44e8a968e3
8 changed files with 399 additions and 118 deletions
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99
src/bin/psql/common.c
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@@ -3,7 +3,7 @@
*
* Copyright (c) 2000-2004, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/bin/psql/common.c,v 1.92 2004/10/10 23:37:40 neilc Exp $
* $PostgreSQL: pgsql/src/bin/psql/common.c,v 1.93 2004/10/30 23:10:50 tgl Exp $
*/
#include "postgres_fe.h"
#include "common.h"
@@ -223,23 +223,33 @@ NoticeProcessor(void *arg, const char *message)
*
* Before we start a query, we enable a SIGINT signal catcher that sends a
* cancel request to the backend. Note that sending the cancel directly from
* the signal handler is safe because PQrequestCancel() is written to make it
* so. We use write() to print to stdout because it's better to use simple
* the signal handler is safe because PQcancel() is written to make it
* so. We use write() to print to stderr because it's better to use simple
* facilities in a signal handler.
*
* On win32, the signal cancelling happens on a separate thread, because
* that's how SetConsoleCtrlHandler works. The PQcancel function is safe
* for this (unlike PQrequestCancel). However, a CRITICAL_SECTION is required
* to protect the PGcancel structure against being changed while the other
* thread is using it.
*/
static PGconn *volatile cancelConn = NULL;
static PGcancel *cancelConn = NULL;
#ifdef WIN32
static CRITICAL_SECTION cancelConnLock;
#endif
volatile bool cancel_pressed = false;
#define write_stderr(str) write(fileno(stderr), str, strlen(str))
#ifndef WIN32
#define write_stderr(String) write(fileno(stderr), String, strlen(String))
void
handle_sigint(SIGNAL_ARGS)
{
int save_errno = errno;
char errbuf[256];
/* Don't muck around if prompting for a password. */
if (prompt_state)
@@ -250,17 +260,60 @@ handle_sigint(SIGNAL_ARGS)
cancel_pressed = true;
if (PQrequestCancel(cancelConn))
if (PQcancel(cancelConn, errbuf, sizeof(errbuf)))
write_stderr("Cancel request sent\n");
else
{
write_stderr("Could not send cancel request: ");
write_stderr(PQerrorMessage(cancelConn));
write_stderr(errbuf);
}
errno = save_errno; /* just in case the write changed it */
}
#endif /* not WIN32 */
#else /* WIN32 */
static BOOL WINAPI
consoleHandler(DWORD dwCtrlType)
{
char errbuf[256];
if (dwCtrlType == CTRL_C_EVENT ||
dwCtrlType == CTRL_BREAK_EVENT)
{
if (prompt_state)
return TRUE;
/* Perform query cancel */
EnterCriticalSection(&cancelConnLock);
if (cancelConn != NULL)
{
cancel_pressed = true;
if (PQcancel(cancelConn, errbuf, sizeof(errbuf)))
write_stderr("Cancel request sent\n");
else
{
write_stderr("Could not send cancel request: ");
write_stderr(errbuf);
}
}
LeaveCriticalSection(&cancelConnLock);
return TRUE;
}
else
/* Return FALSE for any signals not being handled */
return FALSE;
}
void
setup_cancel_handler(void)
{
InitializeCriticalSection(&cancelConnLock);
SetConsoleCtrlHandler(consoleHandler, TRUE);
}
#endif /* WIN32 */
/* ConnectionUp
@@ -327,20 +380,42 @@ CheckConnection(void)
static void
SetCancelConn(void)
{
cancelConn = pset.db;
#ifdef WIN32
EnterCriticalSection(&cancelConnLock);
#endif
/* Free the old one if we have one */
if (cancelConn != NULL)
PQfreeCancel(cancelConn);
cancelConn = PQgetCancel(pset.db);
#ifdef WIN32
LeaveCriticalSection(&cancelConnLock);
#endif
}
/*
* ResetCancelConn
*
* Set cancelConn to NULL. I don't know what this means exactly, but it saves
* having to export the variable.
* Free the current cancel connection, if any, and set to NULL.
*/
void
ResetCancelConn(void)
{
#ifdef WIN32
EnterCriticalSection(&cancelConnLock);
#endif
if (cancelConn)
PQfreeCancel(cancelConn);
cancelConn = NULL;
#ifdef WIN32
LeaveCriticalSection(&cancelConnLock);
#endif
}