[CF 5353] v8 - Allow default \watch interval in psql to be configured

This branch was automatically generated by a robot using patches from an email thread registered at: https://commitfest.postgresql.org//5353 The branch will be overwritten each time a new version is posted to the thread, and also periodically to check for bitrot caused by changes on the master branch. (es): https://www.postgresql.org/message-id/[email protected] Author(s): Daniel Gustafsson

Author: Commitfest Bot

doc/src/sgml/ref/psql-ref.sgml

@@ -3852,6 +3852,8 @@ SELECT 1 \bind \sendpipeline
 until interrupted, or the query fails, or the execution count limit
 (if given) is reached, or the query no longer returns the minimum number
 of rows. Wait the specified number of seconds (default 2) between executions.
+The default wait can be changed with the variable
+<xref linkend="app-psql-variables-watch-interval"/>).
 For backwards compatibility,
 <replaceable class="parameter">seconds</replaceable> can be specified
 with or without an <literal>interval=</literal> prefix.
@@ -4746,6 +4748,17 @@ bar
 </listitem>
 </varlistentry>
 
+<varlistentry id="app-psql-variables-watch-interval">
+<term><varname>WATCH_INTERVAL</varname></term>
+<listitem>
+<para>
+This variable sets the default interval which <command>\watch</command>
+waits between executing the query. Specifying an interval in the
+command overrides this variable.
+</para>
+</listitem>
+</varlistentry>
+
 </variablelist>
 
 </refsect3>

src/bin/psql/command.c

@@ -3278,7 +3278,7 @@ exec_command_watch(PsqlScanState scan_state, bool active_branch,
 bool have_sleep = false;
 bool have_iter = false;
 bool have_min_rows = false;
-double sleep = 2;
+double sleep = pset.watch_interval;
 int iter = 0;
 int min_rows = 0;
 
@@ -3292,7 +3292,9 @@ exec_command_watch(PsqlScanState scan_state, bool active_branch,
 /*
 * Parse arguments. We allow either an unlabeled interval or
 * "name=value", where name is from the set ('i', 'interval', 'c',
-* 'count', 'm', 'min_rows').
+* 'count', 'm', 'min_rows'). The parsing of interval value should
+* be kept in sync with ParseVariableDouble which is used for setting
+* the default interval value.
 */
 while (success)
 {

src/bin/psql/help.c

@@ -460,6 +460,8 @@ helpVariables(unsigned short int pager)
 " VERSION_NAME\n"
 " VERSION_NUM\n"
 " psql's version (in verbose string, short string, or numeric format)\n");
+HELP0(" WATCH_INTERVAL\n"
+" number of seconds \\watch by default waits between executing the query buffer\n");
 
 HELP0("\nDisplay settings:\n");
 HELP0("Usage:\n");

src/bin/psql/settings.h

@@ -27,6 +27,12 @@
 #define DEFAULT_PROMPT2 "%/%R%x%# "
 #define DEFAULT_PROMPT3 ">> "
 
+#define DEFAULT_WATCH_INTERVAL "2"
+/*
+* Limit the max default setting to a value which should be safe for the
+* itimer call, yet large enough to cover all realistic usecases.
+*/
+#define DEFAULT_WATCH_INTERVAL_MAX (1000*1000)
 /*
 * Note: these enums should generally be chosen so that zero corresponds
 * to the default behavior.
@@ -166,6 +172,7 @@ typedef struct _psqlSettings
 int fetch_count;
 int histsize;
 int ignoreeof;
+double watch_interval;
 PSQL_ECHO	echo;
 PSQL_ECHO_HIDDEN echo_hidden;
 PSQL_ERROR_ROLLBACK on_error_rollback;

src/bin/psql/startup.c

@@ -944,6 +944,21 @@ histsize_hook(const char *newval)
 return ParseVariableNum(newval, "HISTSIZE", &pset.histsize);
 }
 
+static char *
+watch_interval_substitute_hook(char *newval)
+{
+if (newval == NULL)
+newval = pg_strdup(DEFAULT_WATCH_INTERVAL);
+return newval;
+}
+
+static bool
+watch_interval_hook(const char *newval)
+{
+return ParseVariableDouble(newval, "WATCH_INTERVAL", &pset.watch_interval,
+0, DEFAULT_WATCH_INTERVAL_MAX);
+}
+
 static char *
 ignoreeof_substitute_hook(char *newval)
 {
@@ -1270,4 +1285,7 @@ EstablishVariableSpace(void)
 SetVariableHooks(pset.vars, "HIDE_TABLEAM",
 bool_substitute_hook,
 hide_tableam_hook);
+SetVariableHooks(pset.vars, "WATCH_INTERVAL",
+watch_interval_substitute_hook,
+watch_interval_hook);
 }

src/bin/psql/t/001_basic.pl

@@ -375,6 +375,12 @@ sub psql_fails_like
 $node, sprintf('SELECT 1 \watch c=3 i=%g', 0.0001),
 qr/1\n1\n1/, '\watch with 3 iterations, interval of 0.0001');
 
+# Test zero interval
+psql_like(
+$node, '\set WATCH_INTERVAL 0
+SELECT 1 \watch c=3',
+qr/1\n1\n1/, '\watch with 3 iterations, interval of 0');
+
 # Check \watch minimum row count
 psql_fails_like(
 $node,
@@ -426,6 +432,24 @@ sub psql_fails_like
 qr/iteration count is specified more than once/,
 '\watch, iteration count is specified more than once');
 
+# Check WATCH_INTERVAL
+psql_like(
+$node,
+'\echo :WATCH_INTERVAL
+\set WATCH_INTERVAL 0.001
+\echo :WATCH_INTERVAL
+\unset WATCH_INTERVAL
+\echo :WATCH_INTERVAL',
+qr/^2$
+^0.001$
+^2$/m,
+'WATCH_INTERVAL variable is set and updated');
+psql_fails_like(
+$node,
+'\set WATCH_INTERVAL 1e500',
+qr/is out of range/,
+'WATCH_INTERVAL variable is out of range');
+
 # Test \g output piped into a program.
 # The program is perl -pe '' to simply copy the input to the output.
 my $g_file = "$tempdir/g_file_1.out";

src/bin/psql/variables.c

@@ -7,6 +7,8 @@
 */
 #include "postgres_fe.h"
 
+#include <math.h>
+
 #include "common.h"
 #include "common/logging.h"
 #include "variables.h"
@@ -179,6 +181,74 @@ ParseVariableNum(const char *value, const char *name, int *result)
 }
 }
 
+/*
+* Try to interpret "value" as a double value, and if successful store it in
+* *result. If unsuccessful, *result isn't clobbered. "name" is the variable
+* which is being assigned, the value of which is only used to produce a good
+* error message. Pass NULL as the name to suppress the error message. The
+* value must be within the range [min,max] in order to be considered valid.
+*
+* Returns true, with *result containing the interpreted value, if "value" is
+* syntactically valid, else false (with *result unchanged).
+*/
+bool
+ParseVariableDouble(const char *value, const char *name, double *result, double min, double max)
+{
+char *end;
+double dblval;
+
+/*
+* Empty-string input has historically been treated differently by strtod
+* on various platforms, so handle that by specifically checking for it.
+*/
+if ((value == NULL) || (*value == '\0'))
+{
+if (name)
+pg_log_error("invalid input syntax for \"%s\"", name);
+return false;
+}
+
+errno = 0;
+dblval = strtod(value, &end);
+if (errno == 0 && *end == '\0' && end != value)
+{
+if (dblval < min)
+{
+if (name)
+pg_log_error("invalid value \"%s\" for \"%s\": must be greater than %.2f",
+value, name, min);
+return false;
+}
+else if (dblval > max)
+{
+if (name)
+pg_log_error("invalid value \"%s\" for \"%s\": must be less than %.2f",
+value, name, max);
+}
+*result = dblval;
+return true;
+}
+
+/*
+* Cater for platforms which treat values which aren't zero, but that are
+* too close to zero to have full precision, by checking for zero or real
+* out-of-range values.
+*/
+else if ((errno = ERANGE) &&
+(dblval == 0.0 || dblval >= HUGE_VAL || dblval <= -HUGE_VAL))
+{
+if (name)
+pg_log_error("\"%s\" is out of range for \"%s\"", value, name);
+return false;
+}
+else
+{
+if (name)
+pg_log_error("invalid value \"%s\" for \"%s\"", value, name);
+return false;
+}
+}
+
 /*
 * Print values of all variables.
 */

src/bin/psql/variables.h

@@ -81,6 +81,9 @@ bool ParseVariableBool(const char *value, const char *name,
 bool ParseVariableNum(const char *value, const char *name,
 int *result);
 
+bool ParseVariableDouble(const char *value, const char *name,
+double *result, double min, double max);
+
 void PrintVariables(VariableSpace space);
 
 bool SetVariable(VariableSpace space, const char *name, const char *value);