postgres.git / summary / log / commit / refs

commit    e3da0d4d1a47e2049ae16aa30bb7bf3105dc8c45
Author:   Fujii Masao <fujii@postgresql.org>
Date:     Wed Aug 06 05:49:43 2014 +0000
First released in: 9.5.0, 9.4.0

    Change ParseConfigFp() so that it doesn't process unused entry of each parameter.
    
    When more than one setting entries of same parameter exist in the
    configuration file, PostgreSQL uses only entry appearing last in
    configuration file scan. Since the other entries are not used,
    ParseConfigFp() doesn't need to process them, but previously it did
    that. This problematic behavior caused the configuration file scan
    to detect invalid settings of unused entries (e.g., existence of
    multiple entries of PGC_POSTMASTER parameter) and log the messages
    complaining about them.
    
    This commit changes the configuration file scan so that it processes
    only last entry of each parameter.
    
    Note that when multiple entries of same parameter exist both in
    postgresql.conf and postgresql.auto.conf, unused entries in
    postgresql.conf are still processed only at postmaster startup.
    
    The problem has existed since old version, but a user is more likely
    to encounter it since 9.4 where ALTER SYSTEM command was introduced.
    So back-patch to 9.4.
    
    Amit Kapila, slightly modified by me. Per report from Christoph Berg.


 src/backend/utils/misc/guc-file.l | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/src/backend/utils/misc/guc-file.l b/src/backend/utils/misc/guc-file.l
index 7d301055dd3..e6e11090abd 100644
--- a/src/backend/utils/misc/guc-file.l
+++ b/src/backend/utils/misc/guc-file.l
@@ -562,7 +562,9 @@ ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
 	{
 		char	   *opt_name = NULL;
 		char	   *opt_value = NULL;
-		ConfigVariable *item;
+		ConfigVariable *item,
+					   *cur_item = NULL,
+					   *prev_item = NULL;
 
 		if (token == GUC_EOL)	/* empty or comment line */
 			continue;
@@ -645,13 +647,41 @@ ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
 		}
 		else
 		{
-			/* ordinary variable, append to list */
+			/*
+			 * ordinary variable, append to list.  For multiple items of
+			 * same parameter, retain only which comes later.
+			 */
 			item = palloc(sizeof *item);
 			item->name = opt_name;
 			item->value = opt_value;
 			item->filename = pstrdup(config_file);
 			item->sourceline = ConfigFileLineno-1;
 			item->next = NULL;
+
+			/* Remove the existing item of same parameter from the list */
+			for (cur_item = *head_p; cur_item; prev_item = cur_item,
+					 cur_item = cur_item->next)
+			{
+				if (strcmp(item->name, cur_item->name) == 0)
+				{
+					if (prev_item == NULL)
+						*head_p = cur_item->next;
+					else
+					{
+						prev_item->next = cur_item->next;
+						/*
+						 * On removing last item in list, we need to update tail
+						 * to ensure that list will be maintianed.
+						 */
+						if (prev_item->next == NULL)
+							*tail_p = prev_item;
+					}
+
+					pfree(cur_item);
+					break;
+				}
+			}
+
 			if (*head_p == NULL)
 				*head_p = item;
 			else


[parent: 49d1e03d64f3]