Refactor some code related to backend statistics

This commit changes the way pending backend statistics are tracked by
moving them into a new structure called PgStat_BackendPending, removing
PgStat_BackendPendingIO.  PgStat_BackendPending currently only includes
PgStat_PendingIO for the pending I/O stats.

pgstat_flush_backend() is extended with a "flags" argument to control
which parts of the stats of a backend should be flushed.

With this refactoring, it becomes easier to plug into backend statistics
more data.  A patch to add information related to WAL in this stats kind
is under discussion.

Author: Bertrand Drouvot
Discussion: https://postgr.es/m/Z3zqc4o09dM/Ezyz@ip-10-97-1-34.eu-west-3.compute.internal

diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c
index 16a03b8ce15a50dcee7f56cd56c3434e281bda32..34520535d5491908d5e391fb4890e810b565bf7d 100644 (file)
--- a/src/backend/utils/activity/pgstat.c
+++ b/src/backend/utils/activity/pgstat.c
@@ -370,7 +370,7 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
        .shared_size = sizeof(PgStatShared_Backend),
        .shared_data_off = offsetof(PgStatShared_Backend, stats),
        .shared_data_len = sizeof(((PgStatShared_Backend *) 0)->stats),
-       .pending_size = sizeof(PgStat_BackendPendingIO),
+       .pending_size = sizeof(PgStat_BackendPending),
 
        .flush_pending_cb = pgstat_backend_flush_cb,
        .reset_timestamp_cb = pgstat_backend_reset_timestamp_cb,

diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 1f91bfef0a3a3be0895198b2ecefd44d1a27c62e..207bfa3c2769ca01c41f3640880a787bb052ae64 100644 (file)
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -39,23 +39,21 @@ pgstat_fetch_stat_backend(ProcNumber procNumber)
 }
 
 /*
- * Flush out locally pending backend statistics
- *
- * If no stats have been recorded, this function returns false.
+ * Flush out locally pending backend IO statistics.  Locking is managed
+ * by the caller.
  */
-bool
-pgstat_backend_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
+static void
+pgstat_flush_backend_entry_io(PgStat_EntryRef *entry_ref)
 {
-   PgStatShared_Backend *shbackendioent;
-   PgStat_BackendPendingIO *pendingent;
+   PgStatShared_Backend *shbackendent;
+   PgStat_BackendPending *pendingent;
    PgStat_BktypeIO *bktype_shstats;
+   PgStat_PendingIO *pending_io;
 
-   if (!pgstat_lock_entry(entry_ref, nowait))
-       return false;
-
-   shbackendioent = (PgStatShared_Backend *) entry_ref->shared_stats;
-   bktype_shstats = &shbackendioent->stats.stats;
-   pendingent = (PgStat_BackendPendingIO *) entry_ref->pending;
+   shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+   pendingent = (PgStat_BackendPending *) entry_ref->pending;
+   bktype_shstats = &shbackendent->stats.io_stats;
+   pending_io = &pendingent->pending_io;
 
    for (int io_object = 0; io_object < IOOBJECT_NUM_TYPES; io_object++)
    {
@@ -66,15 +64,33 @@ pgstat_backend_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
                instr_time  time;
 
                bktype_shstats->counts[io_object][io_context][io_op] +=
-                   pendingent->counts[io_object][io_context][io_op];
+                   pending_io->counts[io_object][io_context][io_op];
 
-               time = pendingent->pending_times[io_object][io_context][io_op];
+               time = pending_io->pending_times[io_object][io_context][io_op];
 
                bktype_shstats->times[io_object][io_context][io_op] +=
                    INSTR_TIME_GET_MICROSEC(time);
            }
        }
    }
+}
+
+/*
+ * Wrapper routine to flush backend statistics.
+ */
+static bool
+pgstat_flush_backend_entry(PgStat_EntryRef *entry_ref, bool nowait,
+                          bits32 flags)
+{
+   if (!pgstat_tracks_backend_bktype(MyBackendType))
+       return false;
+
+   if (!pgstat_lock_entry(entry_ref, nowait))
+       return false;
+
+   /* Flush requested statistics */
+   if (flags & PGSTAT_BACKEND_FLUSH_IO)
+       pgstat_flush_backend_entry_io(entry_ref);
 
    pgstat_unlock_entry(entry_ref);
 
@@ -82,10 +98,23 @@ pgstat_backend_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
 }
 
 /*
- * Simpler wrapper of pgstat_backend_flush_cb()
+ * Callback to flush out locally pending backend statistics.
+ *
+ * If no stats have been recorded, this function returns false.
+ */
+bool
+pgstat_backend_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
+{
+   return pgstat_flush_backend_entry(entry_ref, nowait, PGSTAT_BACKEND_FLUSH_ALL);
+}
+
+/*
+ * Flush out locally pending backend statistics
+ *
+ * "flags" parameter controls which statistics to flush.
  */
 void
-pgstat_flush_backend(bool nowait)
+pgstat_flush_backend(bool nowait, bits32 flags)
 {
    PgStat_EntryRef *entry_ref;
 
@@ -94,7 +123,7 @@ pgstat_flush_backend(bool nowait)
 
    entry_ref = pgstat_get_entry_ref(PGSTAT_KIND_BACKEND, InvalidOid,
                                     MyProcNumber, false, NULL);
-   (void) pgstat_backend_flush_cb(entry_ref, nowait);
+   (void) pgstat_flush_backend_entry(entry_ref, nowait, flags);
 }
 
 /*
@@ -119,9 +148,9 @@ pgstat_create_backend(ProcNumber procnum)
 }
 
 /*
- * Find or create a local PgStat_BackendPendingIO entry for proc number.
+ * Find or create a local PgStat_BackendPending entry for proc number.
  */
-PgStat_BackendPendingIO *
+PgStat_BackendPending *
 pgstat_prep_backend_pending(ProcNumber procnum)
 {
    PgStat_EntryRef *entry_ref;

diff --git a/src/backend/utils/activity/pgstat_io.c b/src/backend/utils/activity/pgstat_io.c
index f9a1f91dba858336dd7a0b930a8ff56047a3a257..a7445995d32262aa021315e91fc861085e6a0752 100644 (file)
--- a/src/backend/utils/activity/pgstat_io.c
+++ b/src/backend/utils/activity/pgstat_io.c
@@ -81,10 +81,10 @@ pgstat_count_io_op_n(IOObject io_object, IOContext io_context, IOOp io_op, uint3
 
    if (pgstat_tracks_backend_bktype(MyBackendType))
    {
-       PgStat_PendingIO *entry_ref;
+       PgStat_BackendPending *entry_ref;
 
        entry_ref = pgstat_prep_backend_pending(MyProcNumber);
-       entry_ref->counts[io_object][io_context][io_op] += cnt;
+       entry_ref->pending_io.counts[io_object][io_context][io_op] += cnt;
    }
 
    PendingIOStats.counts[io_object][io_context][io_op] += cnt;
@@ -151,10 +151,10 @@ pgstat_count_io_op_time(IOObject io_object, IOContext io_context, IOOp io_op,
 
        if (pgstat_tracks_backend_bktype(MyBackendType))
        {
-           PgStat_PendingIO *entry_ref;
+           PgStat_BackendPending *entry_ref;
 
            entry_ref = pgstat_prep_backend_pending(MyProcNumber);
-           INSTR_TIME_ADD(entry_ref->pending_times[io_object][io_context][io_op],
+           INSTR_TIME_ADD(entry_ref->pending_io.pending_times[io_object][io_context][io_op],
                           io_time);
        }
    }

diff --git a/src/backend/utils/activity/pgstat_relation.c b/src/backend/utils/activity/pgstat_relation.c
index 2cc304f8812abc223d6874d11bb5d27cd136e2a2..09247ba09712a143321bfb2a249a547bb647cebc 100644 (file)
--- a/src/backend/utils/activity/pgstat_relation.c
+++ b/src/backend/utils/activity/pgstat_relation.c
@@ -264,7 +264,7 @@ pgstat_report_vacuum(Oid tableoid, bool shared,
     * VACUUM command has processed all tables and committed.
     */
    pgstat_flush_io(false);
-   pgstat_flush_backend(false);
+   pgstat_flush_backend(false, PGSTAT_BACKEND_FLUSH_IO);
 }
 
 /*
@@ -351,7 +351,7 @@ pgstat_report_analyze(Relation rel,
 
    /* see pgstat_report_vacuum() */
    pgstat_flush_io(false);
-   pgstat_flush_backend(false);
+   pgstat_flush_backend(false, PGSTAT_BACKEND_FLUSH_IO);
 }
 
 /*

diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 3245f3a8d8a59cd44a157793c22f10910de09168..5f8d20a406d429b44c870cc1442e7e73eb3aad8c 100644 (file)
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1544,7 +1544,7 @@ pg_stat_get_backend_io(PG_FUNCTION_ARGS)
    if (bktype == B_INVALID)
        return (Datum) 0;
 
-   bktype_stats = &backend_stats->stats;
+   bktype_stats = &backend_stats->io_stats;
 
    /*
     * In Assert builds, we can afford an extra loop through all of the

diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0d8427f27d174880b214166526875c60dbeeed69..f1dfe2b5e91045dba1aeed47884f71d1ec5c48d3 100644 (file)
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -375,15 +375,24 @@ typedef struct PgStat_IO
    PgStat_BktypeIO stats[BACKEND_NUM_TYPES];
 } PgStat_IO;
 
-/* Backend statistics store the same amount of IO data as PGSTAT_KIND_IO */
-typedef PgStat_PendingIO PgStat_BackendPendingIO;
-
 typedef struct PgStat_Backend
 {
    TimestampTz stat_reset_timestamp;
-   PgStat_BktypeIO stats;
+   PgStat_BktypeIO io_stats;
 } PgStat_Backend;
 
+/* ---------
+ * PgStat_BackendPending   Non-flushed backend stats.
+ * ---------
+ */
+typedef struct PgStat_BackendPending
+{
+   /*
+    * Backend statistics store the same amount of IO data as PGSTAT_KIND_IO.
+    */
+   PgStat_PendingIO pending_io;
+} PgStat_BackendPending;
+
 typedef struct PgStat_StatDBEntry
 {
    PgStat_Counter xact_commit;

diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index 52eb008710f75f0516970009adac7fa0bd692806..4bb8e5c53ab2fcd5b65e26c243f7a181b20395f0 100644 (file)
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -613,9 +613,12 @@ extern void pgstat_archiver_snapshot_cb(void);
  * Functions in pgstat_backend.c
  */
 
-extern void pgstat_flush_backend(bool nowait);
+/* flags for pgstat_flush_backend() */
+#define PGSTAT_BACKEND_FLUSH_IO        (1 << 0)    /* Flush I/O statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL   (PGSTAT_BACKEND_FLUSH_IO)
 
-extern PgStat_BackendPendingIO *pgstat_prep_backend_pending(ProcNumber procnum);
+extern void pgstat_flush_backend(bool nowait, bits32 flags);
+extern PgStat_BackendPending *pgstat_prep_backend_pending(ProcNumber procnum);
 extern bool pgstat_backend_flush_cb(PgStat_EntryRef *entry_ref, bool nowait);
 extern void pgstat_backend_reset_timestamp_cb(PgStatShared_Common *header, TimestampTz ts);
 

diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 9f83ecf181f9e654eb12c45bb3951946f7c806ce..eb93debe1088aacfa2a843d1931fc38e61bea3d7 100644 (file)
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2140,7 +2140,7 @@ PgStatShared_Subscription
 PgStatShared_Wal
 PgStat_ArchiverStats
 PgStat_Backend
-PgStat_BackendPendingIO
+PgStat_BackendPending
 PgStat_BackendSubEntry
 PgStat_BgWriterStats
 PgStat_BktypeIO