From a0c2492b957a7e89b997d03d0d62f37fee7aafdf Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 3 Apr 2013 14:13:34 -0400
Subject: [PATCH] Avoid updating our PgBackendStatus entry when
track_activities is off.
The point of turning off track_activities is to avoid this reporting
overhead, but a thinko in commit 4f42b546fd87a80be30c53a0f2c897acb826ad52
caused pgstat_report_activity() to perform half of its updates anyway.
Fix that, and also make sure that we clear all the now-disabled fields
when transitioning to the non-reporting state.
---
src/backend/postmaster/pgstat.c | 42 ++++++++++++++++-------------
src/backend/utils/adt/pgstatfuncs.c | 11 ++------
2 files changed, 25 insertions(+), 28 deletions(-)
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index f890e2bc663..edad1401e45 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -2520,7 +2520,7 @@ pgstat_beshutdown_hook(int code, Datum arg)
* pgstat_report_activity() -
*
* Called from tcop/postgres.c to report what the backend is actually doing
- * (usually "<IDLE>" or the start of the query to be executed).
+ * (but note cmd_str can be NULL for certain cases).
*
* All updates of the status entry follow the protocol of bumping
* st_changecount before and after. We use a volatile pointer here to
@@ -2540,29 +2540,32 @@ pgstat_report_activity(BackendState state, const char *cmd_str)
if (!beentry)
return;
- /*
- * To minimize the time spent modifying the entry, fetch all the needed
- * data first.
- */
- current_timestamp = GetCurrentTimestamp();
-
- if (!pgstat_track_activities && beentry->st_state != STATE_DISABLED)
+ if (!pgstat_track_activities)
{
- /*
- * Track activities is disabled, but we have a non-disabled state set.
- * That means the status changed - so as our last update, tell the
- * collector that we disabled it and will no longer update.
- */
- beentry->st_changecount++;
- beentry->st_state = STATE_DISABLED;
- beentry->st_state_start_timestamp = current_timestamp;
- beentry->st_changecount++;
- Assert((beentry->st_changecount & 1) == 0);
+ if (beentry->st_state != STATE_DISABLED)
+ {
+ /*
+ * track_activities is disabled, but we last reported a
+ * non-disabled state. As our final update, change the state and
+ * clear fields we will not be updating anymore.
+ */
+ beentry->st_changecount++;
+ beentry->st_state = STATE_DISABLED;
+ beentry->st_state_start_timestamp = 0;
+ beentry->st_activity[0] = '\0';
+ beentry->st_activity_start_timestamp = 0;
+ /* st_xact_start_timestamp and st_waiting are also disabled */
+ beentry->st_xact_start_timestamp = 0;
+ beentry->st_waiting = false;
+ beentry->st_changecount++;
+ Assert((beentry->st_changecount & 1) == 0);
+ }
return;
}
/*
- * Fetch more data before we start modifying the entry
+ * To minimize the time spent modifying the entry, fetch all the needed
+ * data first.
*/
start_timestamp = GetCurrentStatementStartTimestamp();
if (cmd_str != NULL)
@@ -2570,6 +2573,7 @@ pgstat_report_activity(BackendState state, const char *cmd_str)
len = pg_mbcliplen(cmd_str, strlen(cmd_str),
pgstat_track_activity_query_size - 1);
}
+ current_timestamp = GetCurrentTimestamp();
/*
* Now update the status entry
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 7c0705abcc9..6f251474857 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -665,15 +665,8 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
nulls[4] = true;
break;
}
- if (beentry->st_state == STATE_UNDEFINED ||
- beentry->st_state == STATE_DISABLED)
- {
- values[5] = CStringGetTextDatum("");
- }
- else
- {
- values[5] = CStringGetTextDatum(beentry->st_activity);
- }
+
+ values[5] = CStringGetTextDatum(beentry->st_activity);
values[6] = BoolGetDatum(beentry->st_waiting);
if (beentry->st_xact_start_timestamp != 0)
--
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