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commit    f1bf619acdff15b88b5729f8de6df4eed609b3a0
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Wed Aug 14 19:09:19 2019 +0000
First released in: 13.0, 9.4.25, 9.5.20, 9.6.16, 10.11, 11.6, 12.0

    Fix ALTER SYSTEM to cope with duplicate entries in postgresql.auto.conf.
    
    ALTER SYSTEM itself normally won't make duplicate entries (although
    up till this patch, it was possible to confuse it by writing case
    variants of a GUC's name).  However, if some external tool has appended
    entries to the file, that could result in duplicate entries for a single
    GUC name.  In such a situation, ALTER SYSTEM did exactly the wrong thing,
    because it replaced or removed only the first matching entry, leaving
    the later one(s) still there and hence still determining the active value.
    
    This patch fixes that by making ALTER SYSTEM sweep through the file and
    remove all matching entries, then (if not ALTER SYSTEM RESET) append the
    new setting to the end.  This means entries will be in order of last
    setting rather than first setting, but that shouldn't hurt anything.
    
    Also, make the comparisons case-insensitive so that the right things
    happen if you do, say, ALTER SYSTEM SET "TimeZone" = 'whatever'.
    
    This has been broken since ALTER SYSTEM was invented, so back-patch
    to all supported branches.
    
    Ian Barwick, with minor mods by me
    
    Discussion: https://postgr.es/m/aed6cc9f-98f3-2693-ac81-52bb0052307e@2ndquadrant.com


 src/backend/utils/misc/guc.c | 47 +++++++++++++++++++++-----------------------
 1 file changed, 22 insertions(+), 25 deletions(-)

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index eb785220539..90ffd893394 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -7837,40 +7837,37 @@ replace_auto_config_value(ConfigVariable **head_p, ConfigVariable **tail_p,
 						  const char *name, const char *value)
 {
 	ConfigVariable *item,
+			   *next,
 			   *prev = NULL;
 
-	/* Search the list for an existing match (we assume there's only one) */
-	for (item = *head_p; item != NULL; item = item->next)
+	/*
+	 * Remove any existing match(es) for "name".  Normally there'd be at most
+	 * one, but if external tools have modified the config file, there could
+	 * be more.
+	 */
+	for (item = *head_p; item != NULL; item = next)
 	{
-		if (strcmp(item->name, name) == 0)
+		next = item->next;
+		if (guc_name_compare(item->name, name) == 0)
 		{
-			/* found a match, replace it */
-			pfree(item->value);
-			if (value != NULL)
-			{
-				/* update the parameter value */
-				item->value = pstrdup(value);
-			}
+			/* found a match, delete it */
+			if (prev)
+				prev->next = next;
 			else
-			{
-				/* delete the configuration parameter from list */
-				if (*head_p == item)
-					*head_p = item->next;
-				else
-					prev->next = item->next;
-				if (*tail_p == item)
-					*tail_p = prev;
+				*head_p = next;
+			if (next == NULL)
+				*tail_p = prev;
 
-				pfree(item->name);
-				pfree(item->filename);
-				pfree(item);
-			}
-			return;
+			pfree(item->name);
+			pfree(item->value);
+			pfree(item->filename);
+			pfree(item);
 		}
-		prev = item;
+		else
+			prev = item;
 	}
 
-	/* Not there; no work if we're trying to delete it */
+	/* Done if we're trying to delete it */
 	if (value == NULL)
 		return;
 


[parent: 9c02cf566143]