diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index d1e628fefcab1ff77931b1e291e7258bcba5d3b6..0cc329691dde66b2d26ab72aa55e8d91ec06c6fb 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -89,6 +89,18 @@ include 'filename'
     Inclusions can be nested.
    </para>
 
+   <para>
+    <indexterm>
+     <primary><literal>include_if_exists</></primary>
+     <secondary>in configuration file</secondary>
+    </indexterm>
+    Use the same approach as the <literal>include</> directive, continuing
+    normally if the file does not exist.  A regular <literal>include</>
+    will stop with an error if the referenced file is missing, while
+    <literal>include_if_exists</> does not.  A warning about the missing
+    file will be logged.
+   </para>
+
    <para>
     <indexterm>
      <primary>SIGHUP</primary>
diff --git a/src/backend/utils/misc/guc-file.l b/src/backend/utils/misc/guc-file.l
index a094c7a2d2d8f651c37a464826fa2d34351543c6..5fe5d14544cd68f9716447fbf188ed42e1fd960f 100644
--- a/src/backend/utils/misc/guc-file.l
+++ b/src/backend/utils/misc/guc-file.l
@@ -129,7 +129,7 @@ ProcessConfigFile(GucContext context)
 	/* Parse the file into a list of option names and values */
 	head = tail = NULL;
 
-	if (!ParseConfigFile(ConfigFileName, NULL, 0, elevel, &head, &tail))
+	if (!ParseConfigFile(ConfigFileName, NULL, true, 0, elevel, &head, &tail))
 	{
 		/* Syntax error(s) detected in the file, so bail out */
 		error = true;
@@ -363,7 +363,7 @@ ProcessConfigFile(GucContext context)
  * and absolute-ifying the path name if necessary.
  */
 bool
-ParseConfigFile(const char *config_file, const char *calling_file,
+ParseConfigFile(const char *config_file, const char *calling_file, bool strict,
 				int depth, int elevel,
 				ConfigVariable **head_p,
 				ConfigVariable **tail_p)
@@ -414,11 +414,19 @@ ParseConfigFile(const char *config_file, const char *calling_file,
 	fp = AllocateFile(config_file, "r");
 	if (!fp)
 	{
-		ereport(elevel,
-				(errcode_for_file_access(),
-				 errmsg("could not open configuration file \"%s\": %m",
+		if (strict)
+		{
+			ereport(elevel,
+					(errcode_for_file_access(),
+					 errmsg("could not open configuration file \"%s\": %m",
+							config_file)));
+			return false;
+		}
+
+		ereport(LOG, 
+				(errmsg("skipping missing configuration file \"%s\"", 
 						config_file)));
-		return false;
+		return OK;
 	}
 
 	OK = ParseConfigFp(fp, config_file, depth, elevel, head_p, tail_p);
@@ -512,7 +520,24 @@ ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
 		}
 
 		/* OK, process the option name and value */
-		if (guc_name_compare(opt_name, "include") == 0)
+		if (guc_name_compare(opt_name, "include_if_exists") == 0)
+		{
+			/*
+			 * An include_if_exists directive isn't a variable and should be
+			 * processed immediately.
+			 */
+			unsigned int save_ConfigFileLineno = ConfigFileLineno;
+
+			if (!ParseConfigFile(opt_value, config_file, false,
+								 depth + 1, elevel,
+								 head_p, tail_p))
+				OK = false;
+			yy_switch_to_buffer(lex_buffer);
+			ConfigFileLineno = save_ConfigFileLineno;
+			pfree(opt_name);
+			pfree(opt_value);
+		}
+		else if (guc_name_compare(opt_name, "include") == 0)
 		{
 			/*
 			 * An include directive isn't a variable and should be processed
@@ -520,7 +545,7 @@ ParseConfigFp(FILE *fp, const char *config_file, int depth, int elevel,
 			 */
 			unsigned int save_ConfigFileLineno = ConfigFileLineno;
 
-			if (!ParseConfigFile(opt_value, config_file,
+			if (!ParseConfigFile(opt_value, config_file, true,
 								 depth + 1, elevel,
 								 head_p, tail_p))
 				OK = false;
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 8e3057a0140093f37c3fc28854e14d34b6c6bfca..52109e533c9ef7dfbcd4c74b27c053614d44e32e 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -111,7 +111,7 @@ typedef struct ConfigVariable
 } ConfigVariable;
 
 extern bool ParseConfigFile(const char *config_file, const char *calling_file,
-				int depth, int elevel,
+				bool strict, int depth, int elevel,
 				ConfigVariable **head_p, ConfigVariable **tail_p);
 extern bool ParseConfigFp(FILE *fp, const char *config_file,
 			  int depth, int elevel,