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psql: add an optional execution-count limit to \watch. 

\watch can now be told to stop after N executions of the query.

With the idea that we might want to add more options to \watch
in future, this patch generalizes the command's syntax to a list
of name=value options, with the interval allowed to omit the name
for backwards compatibility.

Andrey Borodin, reviewed by Kyotaro Horiguchi, Nathan Bossart,
Michael Paquier, Yugo Nagata, and myself

Discussion: https://postgr.es/m/CAAhFRxiZ2-n_L1ErMm9AZjgmUK=qS6VHb+0SaMn8sqqbhF7How@mail.gmail.com
This commit is contained in:
Tom Lane 2023-04-06 13:18:14 -04:00
parent 2820adf775
commit 00beecfe83
6 changed files with 135 additions and 32 deletions
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10
doc/src/sgml/ref/psql-ref.sgml
View File

@ -3551,12 +3551,16 @@ testdb=&gt; <userinput>\setenv LESS -imx4F</userinput>
<varlistentry id="app-psql-meta-command-watch">
<term><literal>\watch [ <replaceable class="parameter">seconds</replaceable> ]</literal></term>
<term><literal>\watch [ i[nterval]=<replaceable class="parameter">seconds</replaceable> ] [ c[ount]=<replaceable class="parameter">times</replaceable> ] [ <replaceable class="parameter">seconds</replaceable> ]</literal></term>
<listitem>
<para>
Repeatedly execute the current query buffer (as <literal>\g</literal> does)
until interrupted or the query fails. Wait the specified number of
seconds (default 2) between executions. Each query result is
until interrupted, or the query fails, or the execution count limit
(if given) is reached. Wait the specified number of
seconds (default 2) between executions. For backwards compatibility,
<replaceable class="parameter">seconds</replaceable> can be specified
with or without an <literal>interval=</literal> prefix.
Each query result is
displayed with a header that includes the <literal>\pset title</literal>
string (if any), the time as of query start, and the delay interval.
</para>

118
src/bin/psql/command.c
View File

@ -162,7 +162,7 @@ static bool do_connect(enum trivalue reuse_previous_specification,
static bool do_edit(const char *filename_arg, PQExpBuffer query_buf,
int lineno, bool discard_on_quit, bool *edited);
static bool do_shell(const char *command);
static bool do_watch(PQExpBuffer query_buf, double sleep);
static bool do_watch(PQExpBuffer query_buf, double sleep, int iter);
static bool lookup_object_oid(EditableObjectType obj_type, const char *desc,
Oid *obj_oid);
static bool get_create_object_cmd(EditableObjectType obj_type, Oid oid,
@ -2759,7 +2759,8 @@ exec_command_write(PsqlScanState scan_state, bool active_branch,
}
/*
* \watch -- execute a query every N seconds
* \watch -- execute a query every N seconds.
* Optionally, stop after M iterations.
*/
static backslashResult
exec_command_watch(PsqlScanState scan_state, bool active_branch,
@ -2769,32 +2770,109 @@ exec_command_watch(PsqlScanState scan_state, bool active_branch,
if (active_branch)
{
char *opt = psql_scan_slash_option(scan_state,
OT_NORMAL, NULL, true);
bool have_sleep = false;
bool have_iter = false;
double sleep = 2;
int iter = 0;
/* Convert optional sleep-length argument */
if (opt)
/*
* Parse arguments. We allow either an unlabeled interval or
* "name=value", where name is from the set ('i', 'interval', 'c',
* 'count').
*/
while (success)
{
char *opt = psql_scan_slash_option(scan_state,
OT_NORMAL, NULL, true);
char *valptr;
char *opt_end;
errno = 0;
sleep = strtod(opt, &opt_end);
if (sleep < 0 || *opt_end || errno == ERANGE)
if (!opt)
break; /* no more arguments */
valptr = strchr(opt, '=');
if (valptr)
{
pg_log_error("\\watch: incorrect interval value '%s'", opt);
free(opt);
resetPQExpBuffer(query_buf);
psql_scan_reset(scan_state);
return PSQL_CMD_ERROR;
/* Labeled argument */
valptr++;
if (strncmp("i=", opt, strlen("i=")) == 0 ||
strncmp("interval=", opt, strlen("interval=")) == 0)
{
if (have_sleep)
{
pg_log_error("\\watch: interval value is specified more than once");
success = false;
}
else
{
have_sleep = true;
errno = 0;
sleep = strtod(valptr, &opt_end);
if (sleep < 0 || *opt_end || errno == ERANGE)
{
pg_log_error("\\watch: incorrect interval value \"%s\"", valptr);
success = false;
}
}
}
else if (strncmp("c=", opt, strlen("c=")) == 0 ||
strncmp("count=", opt, strlen("count=")) == 0)
{
if (have_iter)
{
pg_log_error("\\watch: iteration count is specified more than once");
success = false;
}
else
{
have_iter = true;
errno = 0;
iter = strtoint(valptr, &opt_end, 10);
if (iter <= 0 || *opt_end || errno == ERANGE)
{
pg_log_error("\\watch: incorrect iteration count \"%s\"", valptr);
success = false;
}
}
}
else
{
pg_log_error("\\watch: unrecognized parameter \"%s\"", opt);
success = false;
}
}
else
{
/* Unlabeled argument: take it as interval */
if (have_sleep)
{
pg_log_error("\\watch: interval value is specified more than once");
success = false;
}
else
{
have_sleep = true;
errno = 0;
sleep = strtod(opt, &opt_end);
if (sleep < 0 || *opt_end || errno == ERANGE)
{
pg_log_error("\\watch: incorrect interval value \"%s\"", opt);
success = false;
}
}
}
free(opt);
}
/* If query_buf is empty, recall and execute previous query */
(void) copy_previous_query(query_buf, previous_buf);
/* If we parsed arguments successfully, do the command */
if (success)
{
/* If query_buf is empty, recall and execute previous query */
(void) copy_previous_query(query_buf, previous_buf);
success = do_watch(query_buf, sleep);
success = do_watch(query_buf, sleep, iter);
}
/* Reset the query buffer as though for \r */
resetPQExpBuffer(query_buf);
@ -5071,7 +5149,7 @@ do_shell(const char *command)
* onto a bunch of exec_command's variables to silence stupider compilers.
*/
static bool
do_watch(PQExpBuffer query_buf, double sleep)
do_watch(PQExpBuffer query_buf, double sleep, int iter)
{
long sleep_ms = (long) (sleep * 1000);
printQueryOpt myopt = pset.popt;
@ -5204,6 +5282,10 @@ do_watch(PQExpBuffer query_buf, double sleep)
if (res <= 0)
break;
/* If we have iteration count, check that it's not exceeded yet */
if (iter && (--iter <= 0))
break;
if (pagerpipe && ferror(pagerpipe))
break;

2
src/bin/psql/help.c
View File

@ -200,7 +200,7 @@ slashUsage(unsigned short int pager)
HELP0(" \\gset [PREFIX] execute query and store result in psql variables\n");
HELP0(" \\gx [(OPTIONS)] [FILE] as \\g, but forces expanded output mode\n");
HELP0(" \\q quit psql\n");
HELP0(" \\watch [SEC] execute query every SEC seconds\n");
HELP0(" \\watch [[i=]SEC] [c=N] execute query every SEC seconds, up to N times\n");
HELP0("\n");
HELP0("Help\n");

33
src/bin/psql/t/001_basic.pl
View File

@ -350,21 +350,38 @@ psql_like(
'\copy from with DEFAULT'
);
# Check \watch
psql_like(
$node,
'SELECT 1 \watch c=3 i=0.01',
qr/1\n1\n1/,
'\watch with 3 iterations');
# Check \watch errors
psql_fails_like(
$node,
'SELECT 1;\watch -10',
qr/incorrect interval value '-10'/,
'SELECT 1 \watch -10',
qr/incorrect interval value "-10"/,
'\watch, negative interval');
psql_fails_like(
$node,
'SELECT 1;\watch 10ab',
qr/incorrect interval value '10ab'/,
'\watch incorrect interval');
'SELECT 1 \watch 10ab',
qr/incorrect interval value "10ab"/,
'\watch, incorrect interval');
psql_fails_like(
$node,
'SELECT 1;\watch 10e400',
qr/incorrect interval value '10e400'/,
'\watch out-of-range interval');
'SELECT 1 \watch 10e400',
qr/incorrect interval value "10e400"/,
'\watch, out-of-range interval');
psql_fails_like(
$node,
'SELECT 1 \watch 1 1',
qr/interval value is specified more than once/,
'\watch, interval value is specified more than once');
psql_fails_like(
$node,
'SELECT 1 \watch c=1 c=1',
qr/iteration count is specified more than once/,
'\watch, iteration count is specified more than once');
done_testing();

2
src/test/regress/expected/psql.out
View File

@ -4536,7 +4536,7 @@ invalid command \lo
\timing arg1
\unset arg1
\w arg1
\watch arg1
\watch arg1 arg2
\x arg1
-- \else here is eaten as part of OT_FILEPIPE argument
\w |/no/such/file \else

2
src/test/regress/sql/psql.sql
View File

@ -1022,7 +1022,7 @@ select \if false \\ (bogus \else \\ 42 \endif \\ forty_two;
\timing arg1
\unset arg1
\w arg1
\watch arg1
\watch arg1 arg2
\x arg1
-- \else here is eaten as part of OT_FILEPIPE argument
\w |/no/such/file \else