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psql: Make default \watch interval configurable
The default interval for \watch to wait between executing queries, when executed without a specified interval, was hardcoded to two seconds. This adds the new variable WATCH_INTERVAL which is used to set the default interval, making it configurable for the user. This makes \watch the first command which has a user configurable default setting. Author: Daniel Gustafsson <daniel@yesql.se> Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi> Reviewed-by: Michael Paquier <michael@paquier.xyz> Reviewed-by: Kirill Reshke <reshkekirill@gmail.com> Reviewed-by: Masahiro Ikeda <ikedamsh@oss.nttdata.com> Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at> Reviewed-by: Greg Sabino Mullane <htamfids@gmail.com> Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> Discussion: https://postgr.es/m/B2FD26B4-8F64-4552-A603-5CC3DF1C7103@yesql.se
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‎doc/src/sgml/ref/psql-ref.sgml

Lines changed: 13 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -3852,6 +3852,8 @@ SELECT 1 \bind \sendpipeline
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until interrupted, or the query fails, or the execution count limit
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(if given) is reached, or the query no longer returns the minimum number
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of rows. Wait the specified number of seconds (default 2) between executions.
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The default wait can be changed with the variable
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<xref linkend="app-psql-variables-watch-interval"/>).
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For backwards compatibility,
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<replaceable class="parameter">seconds</replaceable> can be specified
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with or without an <literal>interval=</literal> prefix.
@@ -4746,6 +4748,17 @@ bar
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</listitem>
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</varlistentry>
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4751+
<varlistentry id="app-psql-variables-watch-interval">
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<term><varname>WATCH_INTERVAL</varname></term>
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<listitem>
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<para>
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This variable sets the default interval which <command>\watch</command>
4756+
waits between executing the query. Specifying an interval in the
4757+
command overrides this variable.
4758+
</para>
4759+
</listitem>
4760+
</varlistentry>
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47494762
</variablelist>
47504763

47514764
</refsect3>

‎src/bin/psql/command.c

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3278,7 +3278,7 @@ exec_command_watch(PsqlScanState scan_state, bool active_branch,
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bool have_sleep = false;
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bool have_iter = false;
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bool have_min_rows = false;
3281-
double sleep = 2;
3281+
double sleep = pset.watch_interval;
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int iter = 0;
32833283
int min_rows = 0;
32843284

@@ -3292,7 +3292,9 @@ exec_command_watch(PsqlScanState scan_state, bool active_branch,
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/*
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* Parse arguments. We allow either an unlabeled interval or
32943294
* "name=value", where name is from the set ('i', 'interval', 'c',
3295-
* 'count', 'm', 'min_rows').
3295+
* 'count', 'm', 'min_rows'). The parsing of interval value should be
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* kept in sync with ParseVariableDouble which is used for setting the
3297+
* default interval value.
32963298
*/
32973299
while (success)
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{

‎src/bin/psql/help.c

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -460,6 +460,8 @@ helpVariables(unsigned short int pager)
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" VERSION_NAME\n"
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" VERSION_NUM\n"
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" psql's version (in verbose string, short string, or numeric format)\n");
463+
HELP0(" WATCH_INTERVAL\n"
464+
" number of seconds \\watch by default waits between executing the query buffer\n");
463465

464466
HELP0("\nDisplay settings:\n");
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HELP0("Usage:\n");

‎src/bin/psql/settings.h

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -27,6 +27,12 @@
2727
#define DEFAULT_PROMPT2 "%/%R%x%# "
2828
#define DEFAULT_PROMPT3 ">> "
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30+
#define DEFAULT_WATCH_INTERVAL "2"
31+
/*
32+
* Limit the max default setting to a value which should be safe for the
33+
* itimer call, yet large enough to cover all realistic usecases.
34+
*/
35+
#define DEFAULT_WATCH_INTERVAL_MAX (1000*1000)
3036
/*
3137
* Note: these enums should generally be chosen so that zero corresponds
3238
* to the default behavior.
@@ -166,6 +172,7 @@ typedef struct _psqlSettings
166172
int fetch_count;
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int histsize;
168174
int ignoreeof;
175+
double watch_interval;
169176
PSQL_ECHO echo;
170177
PSQL_ECHO_HIDDEN echo_hidden;
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PSQL_ERROR_ROLLBACK on_error_rollback;

‎src/bin/psql/startup.c

Lines changed: 18 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -944,6 +944,21 @@ histsize_hook(const char *newval)
944944
return ParseVariableNum(newval, "HISTSIZE", &pset.histsize);
945945
}
946946

947+
static char *
948+
watch_interval_substitute_hook(char *newval)
949+
{
950+
if (newval == NULL)
951+
newval = pg_strdup(DEFAULT_WATCH_INTERVAL);
952+
return newval;
953+
}
954+
955+
static bool
956+
watch_interval_hook(const char *newval)
957+
{
958+
return ParseVariableDouble(newval, "WATCH_INTERVAL", &pset.watch_interval,
959+
0, DEFAULT_WATCH_INTERVAL_MAX);
960+
}
961+
947962
static char *
948963
ignoreeof_substitute_hook(char *newval)
949964
{
@@ -1270,4 +1285,7 @@ EstablishVariableSpace(void)
12701285
SetVariableHooks(pset.vars, "HIDE_TABLEAM",
12711286
bool_substitute_hook,
12721287
hide_tableam_hook);
1288+
SetVariableHooks(pset.vars, "WATCH_INTERVAL",
1289+
watch_interval_substitute_hook,
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watch_interval_hook);
12731291
}

‎src/bin/psql/t/001_basic.pl

Lines changed: 24 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -375,6 +375,12 @@ sub psql_fails_like
375375
$node, sprintf('SELECT 1 \watch c=3 i=%g', 0.0001),
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qr/1\n1\n1/, '\watch with 3 iterations, interval of 0.0001');
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378+
# Test zero interval
379+
psql_like(
380+
$node, '\set WATCH_INTERVAL 0
381+
SELECT 1 \watch c=3',
382+
qr/1\n1\n1/, '\watch with 3 iterations, interval of 0');
383+
378384
# Check \watch minimum row count
379385
psql_fails_like(
380386
$node,
@@ -426,6 +432,24 @@ sub psql_fails_like
426432
qr/iteration count is specified more than once/,
427433
'\watch, iteration count is specified more than once');
428434

435+
# Check WATCH_INTERVAL
436+
psql_like(
437+
$node,
438+
'\echo :WATCH_INTERVAL
439+
\set WATCH_INTERVAL 0.001
440+
\echo :WATCH_INTERVAL
441+
\unset WATCH_INTERVAL
442+
\echo :WATCH_INTERVAL',
443+
qr/^2$
444+
^0.001$
445+
^2$/m,
446+
'WATCH_INTERVAL variable is set and updated');
447+
psql_fails_like(
448+
$node,
449+
'\set WATCH_INTERVAL 1e500',
450+
qr/is out of range/,
451+
'WATCH_INTERVAL variable is out of range');
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429453
# Test \g output piped into a program.
430454
# The program is perl -pe '' to simply copy the input to the output.
431455
my $g_file = "$tempdir/g_file_1.out";

‎src/bin/psql/variables.c

Lines changed: 70 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -7,6 +7,8 @@
77
*/
88
#include "postgres_fe.h"
99

10+
#include <math.h>
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1012
#include "common.h"
1113
#include "common/logging.h"
1214
#include "variables.h"
@@ -179,6 +181,74 @@ ParseVariableNum(const char *value, const char *name, int *result)
179181
}
180182
}
181183

184+
/*
185+
* Try to interpret "value" as a double value, and if successful store it in
186+
* *result. If unsuccessful, *result isn't clobbered. "name" is the variable
187+
* which is being assigned, the value of which is only used to produce a good
188+
* error message. Pass NULL as the name to suppress the error message. The
189+
* value must be within the range [min,max] in order to be considered valid.
190+
*
191+
* Returns true, with *result containing the interpreted value, if "value" is
192+
* syntactically valid, else false (with *result unchanged).
193+
*/
194+
bool
195+
ParseVariableDouble(const char *value, const char *name, double *result, double min, double max)
196+
{
197+
char *end;
198+
double dblval;
199+
200+
/*
201+
* Empty-string input has historically been treated differently by strtod
202+
* on various platforms, so handle that by specifically checking for it.
203+
*/
204+
if ((value == NULL) || (*value == '\0'))
205+
{
206+
if (name)
207+
pg_log_error("invalid input syntax for \"%s\"", name);
208+
return false;
209+
}
210+
211+
errno = 0;
212+
dblval = strtod(value, &end);
213+
if (errno == 0 && *end == '\0' && end != value)
214+
{
215+
if (dblval < min)
216+
{
217+
if (name)
218+
pg_log_error("invalid value \"%s\" for \"%s\": must be greater than %.2f",
219+
value, name, min);
220+
return false;
221+
}
222+
else if (dblval > max)
223+
{
224+
if (name)
225+
pg_log_error("invalid value \"%s\" for \"%s\": must be less than %.2f",
226+
value, name, max);
227+
}
228+
*result = dblval;
229+
return true;
230+
}
231+
232+
/*
233+
* Cater for platforms which treat values which aren't zero, but that are
234+
* too close to zero to have full precision, by checking for zero or real
235+
* out-of-range values.
236+
*/
237+
else if ((errno = ERANGE) &&
238+
(dblval == 0.0 || dblval >= HUGE_VAL || dblval <= -HUGE_VAL))
239+
{
240+
if (name)
241+
pg_log_error("\"%s\" is out of range for \"%s\"", value, name);
242+
return false;
243+
}
244+
else
245+
{
246+
if (name)
247+
pg_log_error("invalid value \"%s\" for \"%s\"", value, name);
248+
return false;
249+
}
250+
}
251+
182252
/*
183253
* Print values of all variables.
184254
*/

‎src/bin/psql/variables.h

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -81,6 +81,9 @@ bool ParseVariableBool(const char *value, const char *name,
8181
bool ParseVariableNum(const char *value, const char *name,
8282
int *result);
8383

84+
bool ParseVariableDouble(const char *value, const char *name,
85+
double *result, double min, double max);
86+
8487
void PrintVariables(VariableSpace space);
8588

8689
bool SetVariable(VariableSpace space, const char *name, const char *value);

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