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

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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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15
src/backend/access/transam/xlog.c
View File

@ -4167,7 +4167,7 @@ ReadControlFile(void)
snprintf(wal_segsz_str, sizeof(wal_segsz_str), "%d", wal_segment_size);
SetConfigOption("wal_segment_size", wal_segsz_str, PGC_INTERNAL,
PGC_S_OVERRIDE);
PGC_S_DYNAMIC_DEFAULT);
/* check and update variables dependent on wal_segment_size */
if (ConvertToXSegs(min_wal_size_mb, wal_segment_size) < 2)
@ -4186,7 +4186,7 @@ ReadControlFile(void)
/* Make the initdb settings visible as GUC variables, too */
SetConfigOption("data_checksums", DataChecksumsEnabled() ? "yes" : "no",
PGC_INTERNAL, PGC_S_OVERRIDE);
PGC_INTERNAL, PGC_S_DYNAMIC_DEFAULT);
}
/*
@ -4343,13 +4343,22 @@ XLOGShmemSize(void)
* This isn't an amazingly clean place to do this, but we must wait till
* NBuffers has received its final value, and must do it before using the
* value of XLOGbuffers to do anything important.
*
* We prefer to report this value's source as PGC_S_DYNAMIC_DEFAULT.
* However, if the DBA explicitly set wal_buffers = -1 in the config file,
* then PGC_S_DYNAMIC_DEFAULT will fail to override that and we must force
* the matter with PGC_S_OVERRIDE.
*/
if (XLOGbuffers == -1)
{
char buf[32];
snprintf(buf, sizeof(buf), "%d", XLOGChooseNumBuffers());
SetConfigOption("wal_buffers", buf, PGC_POSTMASTER, PGC_S_OVERRIDE);
SetConfigOption("wal_buffers", buf, PGC_POSTMASTER,
PGC_S_DYNAMIC_DEFAULT);
if (XLOGbuffers == -1) /* failed to apply it? */
SetConfigOption("wal_buffers", buf, PGC_POSTMASTER,
PGC_S_OVERRIDE);
}
Assert(XLOGbuffers > 0);