Hi,
On Thu, Nov 21, 2024 at 10:01:07AM +0900, Michael Paquier wrote:
> On Wed, Nov 20, 2024 at 05:13:18PM +0000, Bertrand Drouvot wrote:
> > I don't have a strong opinion for this particular case here (I think the
> > code
> > is harder to read but yeah there is some code reduction): so I'm fine with
> > v2 too.
>
> Your patch adding backend statistics would be a much better fit to add
> a test for this specific property
Right.
> so let's keep injection_points out
> of it, even if it means that we would have only coverage for
> variable-numbered stats.
Right, and only when per-backend I/O stats goes in.
> So let's keep it simple here, and just set
> .write_to_file to true for both injection_points stats kinds per the
> scope of this thread.
That's fine by me (the code is simple enough anyway). Done that way in v3
attached.
> Another point is that injection_points acts as
> a template for custom pgstats
That was in fact the main reason why I added this test. But well, just
adding the "write_to_file" in the injection test is enough to "show" that this
member does exist. So I'm fine with v3.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
>From 86272b17ecb58c04931eb268d20714a7b389c3af Mon Sep 17 00:00:00 2001
From: Bertrand Drouvot <bertranddrouvot...@gmail.com>
Date: Wed, 20 Nov 2024 08:35:13 +0000
Subject: [PATCH v3] Add a write_to_file member to PgStat_KindInfo
This new member allows the statistics to configure whether or not they want to
be written to the file on disk. That gives more flexiblity to the custom
statistics.
---
src/backend/utils/activity/pgstat.c | 21 +++++++++++++++++--
src/include/utils/pgstat_internal.h | 3 +++
.../injection_points/injection_stats.c | 1 +
.../injection_points/injection_stats_fixed.c | 1 +
4 files changed, 24 insertions(+), 2 deletions(-)
87.1% src/backend/utils/activity/
6.9% src/include/utils/
5.8% src/test/modules/injection_points/
diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c
index ea8c5691e8..4b8c57bb8e 100644
--- a/src/backend/utils/activity/pgstat.c
+++ b/src/backend/utils/activity/pgstat.c
@@ -12,7 +12,8 @@
* Statistics are loaded from the filesystem during startup (by the startup
* process), unless preceded by a crash, in which case all stats are
* discarded. They are written out by the checkpointer process just before
- * shutting down, except when shutting down in immediate mode.
+ * shutting down (if the stat kind allows it), except when shutting down in
+ * immediate mode.
*
* Fixed-numbered stats are stored in plain (non-dynamic) shared memory.
*
@@ -281,6 +282,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
.name = "database",
.fixed_amount = false,
+ .write_to_file = true,
/* so pg_stat_database entries can be seen in all databases */
.accessed_across_databases = true,
@@ -297,6 +299,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
.name = "relation",
.fixed_amount = false,
+ .write_to_file = true,
.shared_size = sizeof(PgStatShared_Relation),
.shared_data_off = offsetof(PgStatShared_Relation, stats),
@@ -311,6 +314,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
.name = "function",
.fixed_amount = false,
+ .write_to_file = true,
.shared_size = sizeof(PgStatShared_Function),
.shared_data_off = offsetof(PgStatShared_Function, stats),
@@ -324,6 +328,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
.name = "replslot",
.fixed_amount = false,
+ .write_to_file = true,
.accessed_across_databases = true,
@@ -340,6 +345,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
.name = "subscription",
.fixed_amount = false,
+ .write_to_file = true,
/* so pg_stat_subscription_stats entries can be seen in all databases */
.accessed_across_databases = true,
@@ -359,6 +365,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
.name = "archiver",
.fixed_amount = true,
+ .write_to_file = true,
.snapshot_ctl_off = offsetof(PgStat_Snapshot, archiver),
.shared_ctl_off = offsetof(PgStat_ShmemControl, archiver),
@@ -374,6 +381,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
.name = "bgwriter",
.fixed_amount = true,
+ .write_to_file = true,
.snapshot_ctl_off = offsetof(PgStat_Snapshot, bgwriter),
.shared_ctl_off = offsetof(PgStat_ShmemControl, bgwriter),
@@ -389,6 +397,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
.name = "checkpointer",
.fixed_amount = true,
+ .write_to_file = true,
.snapshot_ctl_off = offsetof(PgStat_Snapshot, checkpointer),
.shared_ctl_off = offsetof(PgStat_ShmemControl, checkpointer),
@@ -404,6 +413,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
.name = "io",
.fixed_amount = true,
+ .write_to_file = true,
.snapshot_ctl_off = offsetof(PgStat_Snapshot, io),
.shared_ctl_off = offsetof(PgStat_ShmemControl, io),
@@ -421,6 +431,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
.name = "slru",
.fixed_amount = true,
+ .write_to_file = true,
.snapshot_ctl_off = offsetof(PgStat_Snapshot, slru),
.shared_ctl_off = offsetof(PgStat_ShmemControl, slru),
@@ -438,6 +449,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
.name = "wal",
.fixed_amount = true,
+ .write_to_file = true,
.snapshot_ctl_off = offsetof(PgStat_Snapshot, wal),
.shared_ctl_off = offsetof(PgStat_ShmemControl, wal),
@@ -1611,7 +1623,8 @@ pgstat_write_statsfile(XLogRecPtr redo)
char *ptr;
const PgStat_KindInfo *info = pgstat_get_kind_info(kind);
- if (!info || !info->fixed_amount)
+ /* skip if not fixed or this kind does not want to write to the file */
+ if (!info || !info->fixed_amount || !info->write_to_file)
continue;
if (pgstat_is_kind_builtin(kind))
@@ -1660,6 +1673,10 @@ pgstat_write_statsfile(XLogRecPtr redo)
kind_info = pgstat_get_kind_info(ps->key.kind);
+ /* skip if this kind does not want to write to the file */
+ if (!kind_info->write_to_file)
+ continue;
+
/* if not dropped the valid-entry refcount should exist */
Assert(pg_atomic_read_u32(&ps->refcount) > 0);
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index 437db06910..57ac6e87b6 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -213,6 +213,9 @@ typedef struct PgStat_KindInfo
*/
bool accessed_across_databases:1;
+ /* Write or not to the file */
+ bool write_to_file:1;
+
/*
* The size of an entry in the shared stats hash table (pointed to by
* PgStatShared_HashEntry->body). For fixed-numbered statistics, this is
diff --git a/src/test/modules/injection_points/injection_stats.c b/src/test/modules/injection_points/injection_stats.c
index d89d055913..e16b9db284 100644
--- a/src/test/modules/injection_points/injection_stats.c
+++ b/src/test/modules/injection_points/injection_stats.c
@@ -39,6 +39,7 @@ static bool injection_stats_flush_cb(PgStat_EntryRef *entry_ref, bool nowait);
static const PgStat_KindInfo injection_stats = {
.name = "injection_points",
.fixed_amount = false, /* Bounded by the number of points */
+ .write_to_file = true,
/* Injection points are system-wide */
.accessed_across_databases = true,
diff --git a/src/test/modules/injection_points/injection_stats_fixed.c b/src/test/modules/injection_points/injection_stats_fixed.c
index 2fed178b7a..c5b0bb8cf0 100644
--- a/src/test/modules/injection_points/injection_stats_fixed.c
+++ b/src/test/modules/injection_points/injection_stats_fixed.c
@@ -50,6 +50,7 @@ static void injection_stats_fixed_snapshot_cb(void);
static const PgStat_KindInfo injection_stats_fixed = {
.name = "injection_points_fixed",
.fixed_amount = true,
+ .write_to_file = true,
.shared_size = sizeof(PgStat_StatInjFixedEntry),
.shared_data_off = offsetof(PgStatShared_InjectionPointFixed, stats),
--
2.34.1
