mirror of https://github.com/postgres/postgres
Add PSQL_WATCH_PAGER for psql's \watch command.
Allow a pager to be used by the \watch command. This works but isn't very useful with traditional pagers like "less", so use a different environment variable. The popular open source tool "pspg" (also by Pavel) knows how to display the output if you set PSQL_WATCH_PAGER="pspg --stream". To make \watch react quickly when the user quits the pager or presses ^C, and also to increase the accuracy of its timing and decrease the rate of useless context switches, change the main loop of the \watch command to use sigwait() rather than a sleeping/polling loop, on Unix. Supported on Unix only for now (like pspg). Author: Pavel Stehule <pavel.stehule@gmail.com> Author: Thomas Munro <thomas.munro@gmail.com> Discussion: https://postgr.es/m/CAFj8pRBfzUUPz-3gN5oAzto9SDuRSq-TQPfXU_P6h0L7hO%2BEhg%40mail.gmail.com
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@ -3002,6 +3002,16 @@ lo_import 152801
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(such as <filename>more</filename>) is used.
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</para>
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<para>
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When using the <literal>\watch</literal> command to execute a query
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repeatedly, the environment variable <envar>PSQL_WATCH_PAGER</envar>
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is used to find the pager program instead, on Unix systems. This is
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configured separately because it may confuse traditional pagers, but
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can be used to send output to tools that understand
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<application>psql</application>'s output format (such as
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<filename>pspg --stream</filename>).
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</para>
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<para>
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When the <literal>pager</literal> option is <literal>off</literal>, the pager
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program is not used. When the <literal>pager</literal> option is
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@ -4672,6 +4682,24 @@ PSQL_EDITOR_LINENUMBER_ARG='--line '
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><envar>PSQL_WATCH_PAGER</envar></term>
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<listitem>
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<para>
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When a query is executed repeatedly with the <command>\watch</command>
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command, a pager is not used by default. This behavior can be changed
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by setting <envar>PSQL_WATCH_PAGER</envar> to a pager command, on Unix
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systems. The <literal>pspg</literal> pager (not part of
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<productname>PostgreSQL</productname> but available in many open source
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software distributions) can display the output of
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<command>\watch</command> if started with the option
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<literal>--stream</literal>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><envar>PSQLRC</envar></term>
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@ -13,6 +13,7 @@
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#include <utime.h>
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#ifndef WIN32
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#include <sys/stat.h> /* for stat() */
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#include <sys/time.h> /* for setitimer() */
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#include <fcntl.h> /* open() flags */
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#include <unistd.h> /* for geteuid(), getpid(), stat() */
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#else
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@ -4894,8 +4895,17 @@ do_watch(PQExpBuffer query_buf, double sleep)
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const char *strftime_fmt;
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const char *user_title;
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char *title;
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const char *pagerprog = NULL;
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FILE *pagerpipe = NULL;
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int title_len;
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int res = 0;
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#ifndef WIN32
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sigset_t sigalrm_sigchld_sigint;
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sigset_t sigalrm_sigchld;
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sigset_t sigint;
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struct itimerval interval;
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bool done = false;
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#endif
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if (!query_buf || query_buf->len <= 0)
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{
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@ -4903,6 +4913,58 @@ do_watch(PQExpBuffer query_buf, double sleep)
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return false;
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}
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#ifndef WIN32
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sigemptyset(&sigalrm_sigchld_sigint);
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sigaddset(&sigalrm_sigchld_sigint, SIGCHLD);
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sigaddset(&sigalrm_sigchld_sigint, SIGALRM);
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sigaddset(&sigalrm_sigchld_sigint, SIGINT);
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sigemptyset(&sigalrm_sigchld);
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sigaddset(&sigalrm_sigchld, SIGCHLD);
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sigaddset(&sigalrm_sigchld, SIGALRM);
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sigemptyset(&sigint);
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sigaddset(&sigint, SIGINT);
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/*
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* Block SIGALRM and SIGCHLD before we start the timer and the pager (if
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* configured), to avoid races. sigwait() will receive them.
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*/
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sigprocmask(SIG_BLOCK, &sigalrm_sigchld, NULL);
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/*
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* Set a timer to interrupt sigwait() so we can run the query at the
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* requested intervals.
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*/
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interval.it_value.tv_sec = sleep_ms / 1000;
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interval.it_value.tv_usec = (sleep_ms % 1000) * 1000;
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interval.it_interval = interval.it_value;
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if (setitimer(ITIMER_REAL, &interval, NULL) < 0)
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{
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pg_log_error("could not set timer: %m");
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done = true;
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}
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#endif
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/*
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* For \watch, we ignore the size of the result and always use the pager
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* if PSQL_WATCH_PAGER is set. We also ignore the regular PSQL_PAGER or
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* PAGER environment variables, because traditional pagers probably won't
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* be very useful for showing a stream of results.
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*/
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#ifndef WIN32
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pagerprog = getenv("PSQL_WATCH_PAGER");
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#endif
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if (pagerprog && myopt.topt.pager)
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{
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disable_sigpipe_trap();
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pagerpipe = popen(pagerprog, "w");
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if (!pagerpipe)
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/* silently proceed without pager */
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restore_sigpipe_trap();
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}
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/*
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* Choose format for timestamps. We might eventually make this a \pset
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* option. In the meantime, using a variable for the format suppresses
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@ -4911,10 +4973,12 @@ do_watch(PQExpBuffer query_buf, double sleep)
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strftime_fmt = "%c";
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/*
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* Set up rendering options, in particular, disable the pager, because
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* nobody wants to be prompted while watching the output of 'watch'.
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* Set up rendering options, in particular, disable the pager unless
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* PSQL_WATCH_PAGER was successfully launched.
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*/
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myopt.topt.pager = 0;
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if (!pagerpipe)
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myopt.topt.pager = 0;
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/*
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* If there's a title in the user configuration, make sure we have room
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@ -4929,7 +4993,6 @@ do_watch(PQExpBuffer query_buf, double sleep)
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{
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time_t timer;
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char timebuf[128];
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long i;
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/*
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* Prepare title for output. Note that we intentionally include a
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@ -4948,7 +5011,7 @@ do_watch(PQExpBuffer query_buf, double sleep)
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myopt.title = title;
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/* Run the query and print out the results */
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res = PSQLexecWatch(query_buf->data, &myopt);
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res = PSQLexecWatch(query_buf->data, &myopt, pagerpipe);
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/*
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* PSQLexecWatch handles the case where we can no longer repeat the
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@ -4957,6 +5020,11 @@ do_watch(PQExpBuffer query_buf, double sleep)
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if (res <= 0)
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break;
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if (pagerpipe && ferror(pagerpipe))
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break;
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#ifdef WIN32
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/*
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* Set up cancellation of 'watch' via SIGINT. We redo this each time
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* through the loop since it's conceivable something inside
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@ -4967,12 +5035,10 @@ do_watch(PQExpBuffer query_buf, double sleep)
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/*
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* Enable 'watch' cancellations and wait a while before running the
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* query again. Break the sleep into short intervals (at most 1s)
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* since pg_usleep isn't interruptible on some platforms.
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* query again. Break the sleep into short intervals (at most 1s).
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*/
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sigint_interrupt_enabled = true;
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i = sleep_ms;
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while (i > 0)
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for (long i = sleep_ms; i > 0;)
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{
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long s = Min(i, 1000L);
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i -= s;
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}
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sigint_interrupt_enabled = false;
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#else
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/* sigwait() will handle SIGINT. */
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sigprocmask(SIG_BLOCK, &sigint, NULL);
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if (cancel_pressed)
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done = true;
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/* Wait for SIGINT, SIGCHLD or SIGALRM. */
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while (!done)
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{
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int signal_received;
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if (sigwait(&sigalrm_sigchld_sigint, &signal_received) < 0)
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{
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/* Some other signal arrived? */
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if (errno == EINTR)
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continue;
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else
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{
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pg_log_error("could not wait for signals: %m");
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done = true;
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break;
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}
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}
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/* On ^C or pager exit, it's time to stop running the query. */
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if (signal_received == SIGINT || signal_received == SIGCHLD)
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done = true;
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/* Otherwise, we must have SIGALRM. Time to run the query again. */
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break;
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}
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/* Unblock SIGINT so that slow queries can be interrupted. */
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sigprocmask(SIG_UNBLOCK, &sigint, NULL);
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if (done)
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break;
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#endif
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}
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if (pagerpipe)
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{
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pclose(pagerpipe);
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restore_sigpipe_trap();
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}
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#ifndef WIN32
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/* Disable the interval timer. */
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memset(&interval, 0, sizeof(interval));
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setitimer(ITIMER_REAL, &interval, NULL);
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/* Unblock SIGINT, SIGCHLD and SIGALRM. */
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sigprocmask(SIG_UNBLOCK, &sigalrm_sigchld_sigint, NULL);
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#endif
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pg_free(title);
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return (res >= 0);
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}
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@ -592,12 +592,13 @@ PSQLexec(const char *query)
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* e.g., because of the interrupt, -1 on error.
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*/
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int
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PSQLexecWatch(const char *query, const printQueryOpt *opt)
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PSQLexecWatch(const char *query, const printQueryOpt *opt, FILE *printQueryFout)
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{
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PGresult *res;
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double elapsed_msec = 0;
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instr_time before;
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instr_time after;
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FILE *fout;
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if (!pset.db)
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{
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return 0;
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}
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fout = printQueryFout ? printQueryFout : pset.queryFout;
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switch (PQresultStatus(res))
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{
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case PGRES_TUPLES_OK:
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printQuery(res, opt, pset.queryFout, false, pset.logfile);
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printQuery(res, opt, fout, false, pset.logfile);
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break;
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case PGRES_COMMAND_OK:
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fprintf(pset.queryFout, "%s\n%s\n\n", opt->title, PQcmdStatus(res));
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fprintf(fout, "%s\n%s\n\n", opt->title, PQcmdStatus(res));
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break;
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case PGRES_EMPTY_QUERY:
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PQclear(res);
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fflush(pset.queryFout);
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fflush(fout);
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/* Possible microtiming output */
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if (pset.timing)
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@ -29,7 +29,7 @@ extern sigjmp_buf sigint_interrupt_jmp;
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extern void psql_setup_cancel_handler(void);
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extern PGresult *PSQLexec(const char *query);
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extern int PSQLexecWatch(const char *query, const printQueryOpt *opt);
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extern int PSQLexecWatch(const char *query, const printQueryOpt *opt, FILE *printQueryFout);
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extern bool SendQuery(const char *query);
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* Windows builds currently print one more line than non-Windows builds.
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* Using the larger number is fine.
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*/
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output = PageOutput(158, pager ? &(pset.popt.topt) : NULL);
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output = PageOutput(160, pager ? &(pset.popt.topt) : NULL);
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fprintf(output, _("List of specially treated variables\n\n"));
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" alternative location for the command history file\n"));
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fprintf(output, _(" PSQL_PAGER, PAGER\n"
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" name of external pager program\n"));
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#ifndef WIN32
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fprintf(output, _(" PSQL_WATCH_PAGER\n"
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" name of external pager program used for \\watch\n"));
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#endif
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fprintf(output, _(" PSQLRC\n"
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" alternative location for the user's .psqlrc file\n"));
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fprintf(output, _(" SHELL\n"
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@ -110,6 +110,13 @@ log_locus_callback(const char **filename, uint64 *lineno)
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}
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}
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#ifndef WIN32
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static void
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empty_signal_handler(SIGNAL_ARGS)
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{
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}
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#endif
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/*
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*
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* main
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psql_setup_cancel_handler();
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#ifndef WIN32
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/*
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* do_watch() needs signal handlers installed (otherwise sigwait() will
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* filter them out on some platforms), but doesn't need them to do
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* anything, and they shouldn't ever run (unless perhaps a stray SIGALRM
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* arrives due to a race when do_watch() cancels an itimer).
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*/
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pqsignal(SIGCHLD, empty_signal_handler);
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pqsignal(SIGALRM, empty_signal_handler);
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#endif
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PQsetNoticeProcessor(pset.db, NoticeProcessor, NULL);
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SyncVariables();
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