Unconditionally write the statsfile when SIGHUP is received, to minimize

mhagander · mhagander · commit f1e237b6b2e1 · 2008-08-25T18:55:43.000Z
the window during which backends have no statistics file to read.
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.188 2008/08/25 15:11:00 mha Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.189 2008/08/25 18:55:43 mha Exp $ -->
 
 <chapter Id="runtime-config">
   <title>Server Configuration</title>
@@ -3419,8 +3419,8 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         <filename>pg_stat_tmp</filename>. Pointing this at a RAM based filesystem
         will decrease physical I/O requirements and can lead to increased 
         performance. If this parameter is changed when the system is running,
-        the statistics functions might return no information until a new 
-        file has been written, which typically happens twice per second.
+		there is a small window of time until the new file has been written 
+		during which the statistics functions might return no information.
        </para>
       </listitem>
      </varlistentry>
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
@@ -13,7 +13,7 @@
  *
  *	Copyright (c) 2001-2008, PostgreSQL Global Development Group
  *
- *	$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.180 2008/08/25 15:11:00 mha Exp $
+ *	$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.181 2008/08/25 18:55:43 mha Exp $
  * ----------
  */
 #include "postgres.h"
@@ -2638,11 +2638,14 @@ PgstatCollectorMain(int argc, char *argv[])
 
 		/*
 		 * Reload configuration if we got SIGHUP from the postmaster.
+		 * Also, signal a new write of the file, so we drop a new file as
+		 * soon as possible of the directory for it changes.
 		 */
 		if (got_SIGHUP)
 		{
 			ProcessConfigFile(PGC_SIGHUP);
 			got_SIGHUP = false;
+			need_statwrite = true;
 		}
 
 		/*

Original file line number	Diff line number	Diff line change
`@@ -13,7 +13,7 @@`
`13`	`13`	`*`
`14`	`14`	`* Copyright (c) 2001-2008, PostgreSQL Global Development Group`
`15`	`15`	`*`
`16`		`- * $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.180 2008/08/25 15:11:00 mha Exp $`
	`16`	`+ * $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.181 2008/08/25 18:55:43 mha Exp $`
`17`	`17`	`* ----------`
`18`	`18`	`*/`
`19`	`19`	`#include "postgres.h"`
`@@ -2638,11 +2638,14 @@ PgstatCollectorMain(int argc, char *argv[])`
`2638`	`2638`
`2639`	`2639`	`/*`
`2640`	`2640`	`* Reload configuration if we got SIGHUP from the postmaster.`
	`2641`	`+ * Also, signal a new write of the file, so we drop a new file as`
	`2642`	`+ * soon as possible of the directory for it changes.`
`2641`	`2643`	`*/`
`2642`	`2644`	`if (got_SIGHUP)`
`2643`	`2645`	`{`
`2644`	`2646`	`ProcessConfigFile(PGC_SIGHUP);`
`2645`	`2647`	`got_SIGHUP = false;`
	`2648`	`+ need_statwrite = true;`
`2646`	`2649`	`}`
`2647`	`2650`
`2648`	`2651`	`/*`