Re: [UPDATED] A GUC variable to replace PGBE_ACTIVITY_SIZE

*** a/doc/src/sgml/config.sgml
--- b/doc/src/sgml/config.sgml
***************
*** 3331,3336 **** COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
--- 3331,3349 ----
        </listitem>
       </varlistentry>
  
+      <varlistentry id="guc-track-active-query-size" xreflabel="track_active_query_size">
+       <term><varname>track_active_query_size</varname> (<type>integer</type>)</term>
+       <indexterm>
+        <primary><varname>track_active_query_size</> configuration parameter</primary>
+       </indexterm>
+       <listitem>
+        Specifies the maximum number of characters used to track the currently
+        executing command for each active session. This parameter has a value
+        of 1024 by default.
+        Only superusers can change this setting.
+       </listitem>
+      </varlistentry>
+ 
       <varlistentry id="guc-track-counts" xreflabel="track_counts">
        <term><varname>track_counts</varname> (<type>boolean</type>)</term>
        <indexterm>
*** a/src/backend/postmaster/pgstat.c
--- b/src/backend/postmaster/pgstat.c
***************
*** 101,106 ****
--- 101,107 ----
  bool		pgstat_track_activities = false;
  bool		pgstat_track_counts = false;
  int			pgstat_track_functions = TRACK_FUNC_OFF;
+ int			pgstat_track_activity_query_size = PGBE_DEFAULT_ACTIVITY_SIZE;
  
  /*
   * BgWriter global statistics counters (unused in other processes).
***************
*** 2010,2015 **** pgstat_fetch_global(void)
--- 2011,2017 ----
  
  static PgBackendStatus *BackendStatusArray = NULL;
  static PgBackendStatus *MyBEEntry = NULL;
+ static char*			BackendActivityBuffer = NULL;
  
  
  /*
***************
*** 2025,2031 **** BackendStatusShmemSize(void)
  }
  
  /*
!  * Initialize the shared status array during postmaster startup.
   */
  void
  CreateSharedBackendStatus(void)
--- 2027,2052 ----
  }
  
  /*
!  * Ensures that every element of BackendStatusArray has a valid st_activity
!  * pointer.
!  */
! static void
! pgstat_initialize_activity_pointers(void)
! {
! 	Size i;
! 	PgBackendStatus* beentry = BackendStatusArray;
! 	char*			 buffer = BackendActivityBuffer;
! 
! 	for (i = 0; i < MaxBackends; i++) {
! 		beentry->st_activity = buffer;
! 		buffer += pgstat_track_activity_query_size;
! 		beentry++;
! 	}
! }
! 
! /*
!  * Initialize the shared status array & activity buffer during postmaster
!  * startup.
   */
  void
  CreateSharedBackendStatus(void)
***************
*** 2044,2049 **** CreateSharedBackendStatus(void)
--- 2065,2081 ----
  		 */
  		MemSet(BackendStatusArray, 0, size);
  	}
+ 
+ 	size = mul_size(pgstat_track_activity_query_size, MaxBackends);
+ 	BackendActivityBuffer = (char*)
+ 		ShmemInitStruct("Backend Activity Buffer", size, &found);
+ 
+ 	if (!found)
+ 	{
+ 		MemSet(BackendActivityBuffer, 0, size);
+ 	}
+ 
+ 	pgstat_initialize_activity_pointers();
  }
  
  
***************
*** 2128,2134 **** pgstat_bestart(void)
  	beentry->st_waiting = false;
  	beentry->st_activity[0] = '\0';
  	/* Also make sure the last byte in the string area is always 0 */
! 	beentry->st_activity[PGBE_ACTIVITY_SIZE - 1] = '\0';
  
  	beentry->st_changecount++;
  	Assert((beentry->st_changecount & 1) == 0);
--- 2160,2166 ----
  	beentry->st_waiting = false;
  	beentry->st_activity[0] = '\0';
  	/* Also make sure the last byte in the string area is always 0 */
! 	beentry->st_activity[pgstat_track_activity_query_size - 1] = '\0';
  
  	beentry->st_changecount++;
  	Assert((beentry->st_changecount & 1) == 0);
***************
*** 2188,2194 **** pgstat_report_activity(const char *cmd_str)
  	start_timestamp = GetCurrentStatementStartTimestamp();
  
  	len = strlen(cmd_str);
! 	len = pg_mbcliplen(cmd_str, len, PGBE_ACTIVITY_SIZE - 1);
  
  	/*
  	 * Update my status entry, following the protocol of bumping
--- 2220,2226 ----
  	start_timestamp = GetCurrentStatementStartTimestamp();
  
  	len = strlen(cmd_str);
! 	len = pg_mbcliplen(cmd_str, len, pgstat_track_activity_query_size - 1);
  
  	/*
  	 * Update my status entry, following the protocol of bumping
***************
*** 2267,2272 **** pgstat_read_current_status(void)
--- 2299,2305 ----
  	volatile PgBackendStatus *beentry;
  	PgBackendStatus *localtable;
  	PgBackendStatus *localentry;
+ 	char			*localactivity;
  	int			i;
  
  	Assert(!pgStatRunningInCollector);
***************
*** 2278,2283 **** pgstat_read_current_status(void)
--- 2311,2319 ----
  	localtable = (PgBackendStatus *)
  		MemoryContextAlloc(pgStatLocalContext,
  						   sizeof(PgBackendStatus) * MaxBackends);
+ 	localactivity = (char *)
+ 		MemoryContextAlloc(pgStatLocalContext,
+ 						   pgstat_track_activity_query_size * MaxBackends);
  	localNumBackends = 0;
  
  	beentry = BackendStatusArray;
***************
*** 2296,2305 **** pgstat_read_current_status(void)
  			int			save_changecount = beentry->st_changecount;
  
  			/*
! 			 * XXX if PGBE_ACTIVITY_SIZE is really large, it might be best to
! 			 * use strcpy not memcpy for copying the activity string?
  			 */
  			memcpy(localentry, (char *) beentry, sizeof(PgBackendStatus));
  
  			if (save_changecount == beentry->st_changecount &&
  				(save_changecount & 1) == 0)
--- 2332,2345 ----
  			int			save_changecount = beentry->st_changecount;
  
  			/*
! 			 * XXX if pgstat_track_activity_query_size is really large,
! 			 * it might be best to use strcpy not memcpy for copying the
! 			 * activity string?
  			 */
  			memcpy(localentry, (char *) beentry, sizeof(PgBackendStatus));
+ 			memcpy(localactivity, (char *) beentry->st_activity,
+ 					pgstat_track_activity_query_size);
+ 			localentry->st_activity = localactivity;
  
  			if (save_changecount == beentry->st_changecount &&
  				(save_changecount & 1) == 0)
***************
*** 2314,2322 **** pgstat_read_current_status(void)
  		if (localentry->st_procpid > 0)
  		{
  			localentry++;
  			localNumBackends++;
  		}
! 	}
  
  	/* Set the pointer only after completion of a valid table */
  	localBackendStatusTable = localtable;
--- 2354,2363 ----
  		if (localentry->st_procpid > 0)
  		{
  			localentry++;
+ 			localactivity += pgstat_track_activity_query_size;
  			localNumBackends++;
  		}
!  	}
  
  	/* Set the pointer only after completion of a valid table */
  	localBackendStatusTable = localtable;
*** a/src/backend/utils/misc/guc.c
--- b/src/backend/utils/misc/guc.c
***************
*** 1311,1316 **** static struct config_int ConfigureNamesInt[] =
--- 1311,1325 ----
  	},
  
  	{
+ 		{"track_activity_query_size", PGC_POSTMASTER, RESOURCES_MEM,
+ 			gettext_noop("Sets the maximum number of characters that will be displayed for pg_stat_activity.current_query."),
+ 			NULL,
+ 		},
+ 		&pgstat_track_activity_query_size,
+ 		PGBE_DEFAULT_ACTIVITY_SIZE, 100, 102400, NULL, NULL
+ 	},
+ 
+ 	{
  		{"temp_buffers", PGC_USERSET, RESOURCES_MEM,
  			gettext_noop("Sets the maximum number of temporary buffers used by each session."),
  			NULL,
*** a/src/backend/utils/misc/postgresql.conf.sample
--- b/src/backend/utils/misc/postgresql.conf.sample
***************
*** 364,369 ****
--- 364,370 ----
  #track_activities = on
  #track_counts = on
  #track_functions = none			# none, pl, all
+ #track_active_query_size = 1024
  #update_process_title = on
  
  
*** a/src/include/pgstat.h
--- b/src/include/pgstat.h
***************
*** 509,516 **** typedef struct PgStat_GlobalStats
   * ----------
   */
  
! /* Max length of st_activity string ... perhaps replace with a GUC var? */
! #define PGBE_ACTIVITY_SIZE	1024
  
  /* ----------
   * PgBackendStatus
--- 509,516 ----
   * ----------
   */
  
! /* Default length of st_activity string (see backend_activity_size GUC) */
! #define PGBE_DEFAULT_ACTIVITY_SIZE	1024
  
  /* ----------
   * PgBackendStatus
***************
*** 551,557 **** typedef struct PgBackendStatus
  	bool		st_waiting;
  
  	/* current command string; MUST be null-terminated */
! 	char		st_activity[PGBE_ACTIVITY_SIZE];
  } PgBackendStatus;
  
  /*
--- 551,557 ----
  	bool		st_waiting;
  
  	/* current command string; MUST be null-terminated */
! 	char	   *st_activity;
  } PgBackendStatus;
  
  /*
***************
*** 578,583 **** typedef struct PgStat_FunctionCallUsage
--- 578,584 ----
  extern bool pgstat_track_activities;
  extern bool pgstat_track_counts;
  extern int	pgstat_track_functions;
+ extern int	pgstat_track_activity_query_size;
  
  /*
   * BgWriter statistics counters are updated directly by bgwriter and bufmgr