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commit    2791f2180d8e7c469fac2a4d88fc449689e4c970
Author:   Magnus Hagander <magnus@hagander.net>
Date:     Sun May 27 08:54:31 2012 +0000
First released in: 9.2.0, 9.0.8, 9.1.4

    Fix handling of pg_stat_statements.stat temporary file
    
    Write the file to a temporary name and then rename() it into the
    permanent name, to ensure it can't end up half-written and corrupt
    in case of a crash during shutdown.
    
    Unlink the file after it has been read so it's removed from the data
    directory and not included in base backups going to replication slaves.


 contrib/pg_stat_statements/pg_stat_statements.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 0236b87498f..590512fdcdb 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -427,6 +427,13 @@ pgss_shmem_startup(void)
 
 	pfree(buffer);
 	FreeFile(file);
+
+	/*
+	 * Remove the file so it's not included in backups/replication
+	 * slaves, etc. A new file will be written on next shutdown.
+	 */
+	unlink(PGSS_DUMP_FILE);
+
 	return;
 
 error:
@@ -468,7 +475,7 @@ pgss_shmem_shutdown(int code, Datum arg)
 	if (!pgss_save)
 		return;
 
-	file = AllocateFile(PGSS_DUMP_FILE, PG_BINARY_W);
+	file = AllocateFile(PGSS_DUMP_FILE ".tmp", PG_BINARY_W);
 	if (file == NULL)
 		goto error;
 
@@ -494,16 +501,25 @@ pgss_shmem_shutdown(int code, Datum arg)
 		goto error;
 	}
 
+	/*
+	 * Rename file into place, so we atomically replace the old one.
+	 */
+	if (rename(PGSS_DUMP_FILE ".tmp", PGSS_DUMP_FILE) != 0)
+		ereport(LOG,
+				(errcode_for_file_access(),
+				 errmsg("could not rename pg_stat_statement file \"%s\": %m",
+						PGSS_DUMP_FILE ".tmp")));
+
 	return;
 
 error:
 	ereport(LOG,
 			(errcode_for_file_access(),
 			 errmsg("could not write pg_stat_statement file \"%s\": %m",
-					PGSS_DUMP_FILE)));
+					PGSS_DUMP_FILE  ".tmp")));
 	if (file)
 		FreeFile(file);
-	unlink(PGSS_DUMP_FILE);
+	unlink(PGSS_DUMP_FILE ".tmp");
 }
 
 /*


[parent: 6c1bf45ea50a]