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Be more careful about GucSource for internally-driven GUC settings.

Browse Source 
The original advice for hard-wired SetConfigOption calls was to use
PGC_S_OVERRIDE, particularly for PGC_INTERNAL GUCs.  However,
that's really overkill for PGC_INTERNAL GUCs, since there is no
possibility that we need to override a user-provided setting.
Instead use PGC_S_DYNAMIC_DEFAULT in most places, so that the
value will appear with source = 'default' in pg_settings and thereby
not be shown by psql's new \dconfig command.  The one exception is
that when changing in_hot_standby in a hot-standby session, we still
use PGC_S_OVERRIDE, because people felt that seeing that in \dconfig
would be a good thing.

Similarly use PGC_S_DYNAMIC_DEFAULT for the auto-tune value of
wal_buffers (if possible, that is if wal_buffers wasn't explicitly
set to -1), and for the typical 2MB value of max_stack_depth.

In combination these changes remove four not-very-interesting
entries from the typical output of \dconfig, all of which people
fingered as "why is that showing up?" in the discussion thread.

Discussion: https://postgr.es/m/3118455.1649267333@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2022-06-08 13:26:18 -04:00
parent abed46aea4
commit 7ab5b4eb48
9 changed files with 52 additions and 32 deletions
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34
src/backend/utils/misc/guc.c
View File

@@ -5939,6 +5939,8 @@ InitializeGUCOptionsFromEnvironment(void)
* rlimit isn't exactly an "environment variable", but it behaves about
* the same. If we can identify the platform stack depth rlimit, increase
* default stack depth setting up to whatever is safe (but at most 2MB).
* Report the value's source as PGC_S_DYNAMIC_DEFAULT if it's 2MB, or as
* PGC_S_ENV_VAR if it's reflecting the rlimit limit.
*/
stack_rlimit = get_stack_depth_rlimit();
if (stack_rlimit > 0)
@@ -5947,12 +5949,19 @@ InitializeGUCOptionsFromEnvironment(void)
if (new_limit > 100)
{
GucSource source;
char limbuf[16];
new_limit = Min(new_limit, 2048);
sprintf(limbuf, "%ld", new_limit);
if (new_limit < 2048)
source = PGC_S_ENV_VAR;
else
{
new_limit = 2048;
source = PGC_S_DYNAMIC_DEFAULT;
}
snprintf(limbuf, sizeof(limbuf), "%ld", new_limit);
SetConfigOption("max_stack_depth", limbuf,
PGC_POSTMASTER, PGC_S_ENV_VAR);
PGC_POSTMASTER, source);
}
}
}
@@ -6776,12 +6785,16 @@ BeginReportingGUCOptions(void)
reporting_enabled = true;
/*
* Hack for in_hot_standby: initialize with the value we're about to send.
* Hack for in_hot_standby: set the GUC value true if appropriate. This
* is kind of an ugly place to do it, but there's few better options.
*
* (This could be out of date by the time we actually send it, in which
* case the next ReportChangedGUCOptions call will send a duplicate
* report.)
*/
in_hot_standby = RecoveryInProgress();
if (RecoveryInProgress())
SetConfigOption("in_hot_standby", "true",
PGC_INTERNAL, PGC_S_OVERRIDE);
/* Transmit initial values of interesting variables */
for (i = 0; i < num_guc_variables; i++)
@@ -6822,15 +6835,8 @@ ReportChangedGUCOptions(void)
* transition from false to true.
*/
if (in_hot_standby && !RecoveryInProgress())
{
struct config_generic *record;
record = find_option("in_hot_standby", false, false, ERROR);
Assert(record != NULL);
record->status |= GUC_NEEDS_REPORT;
report_needed = true;
in_hot_standby = false;
}
SetConfigOption("in_hot_standby", "false",
PGC_INTERNAL, PGC_S_OVERRIDE);
/* Quick exit if no values have been changed */
if (!report_needed)