Disallow setting bogus GUCs within an extension's reserved namespace.

Commit 75d22069e tried to throw a warning for setting a custom GUC whose
prefix belongs to a previously-loaded extension, if there is no such GUC
defined by the extension.  But that caused unstable behavior with
parallel workers, because workers don't necessarily load extensions and
GUCs in the same order their leader did.  To make that work safely, we
have to completely disallow the case.  We now actually remove any such
GUCs at the time of initial extension load, and then throw an error not
just a warning if you try to add one later.  While this might create a
compatibility issue for a few people, the improvement in error-detection
capability seems worth it; it's hard to believe that there's any good
use-case for choosing such GUC names.

This also un-reverts 5609cc01c (Rename EmitWarningsOnPlaceholders() to
MarkGUCPrefixReserved()), since that function's old name is now even
more of a misnomer.

Florin Irion and Tom Lane

Discussion: https://postgr.es/m/1902182.1640711215@sss.pgh.pa.us

8 files changed, 8 insertions, 8 deletions

diff --git a/contrib/auth_delay/auth_delay.c b/contrib/auth_delay/auth_delay.c
index 38f4276db39..6b94d653ea4 100644
--- a/contrib/auth_delay/auth_delay.c
+++ b/contrib/auth_delay/auth_delay.c
@@ -68,7 +68,7 @@ _PG_init(void)
 							NULL,
 							NULL);
 
-	EmitWarningsOnPlaceholders("auth_delay");
+	MarkGUCPrefixReserved("auth_delay");
 
 	/* Install Hooks */
 	original_client_auth_hook = ClientAuthentication_hook;
diff --git a/contrib/auto_explain/auto_explain.c b/contrib/auto_explain/auto_explain.c
index 3e09abaecac..d3029f85efe 100644
--- a/contrib/auto_explain/auto_explain.c
+++ b/contrib/auto_explain/auto_explain.c
@@ -231,7 +231,7 @@ _PG_init(void)
 							 NULL,
 							 NULL);
 
-	EmitWarningsOnPlaceholders("auto_explain");
+	MarkGUCPrefixReserved("auto_explain");
 
 	/* Install hooks. */
 	prev_ExecutorStart = ExecutorStart_hook;
diff --git a/contrib/basic_archive/basic_archive.c b/contrib/basic_archive/basic_archive.c
index 16ddddccbbc..e7efbfb9c34 100644
--- a/contrib/basic_archive/basic_archive.c
+++ b/contrib/basic_archive/basic_archive.c
@@ -69,7 +69,7 @@ _PG_init(void)
 							   0,
 							   check_archive_directory, NULL, NULL);
 
-	EmitWarningsOnPlaceholders("basic_archive");
+	MarkGUCPrefixReserved("basic_archive");
 
 	basic_archive_context = AllocSetContextCreate(TopMemoryContext,
 												  "basic_archive",
diff --git a/contrib/pg_prewarm/autoprewarm.c b/contrib/pg_prewarm/autoprewarm.c
index 1d4d74b171f..45e012a63a5 100644
--- a/contrib/pg_prewarm/autoprewarm.c
+++ b/contrib/pg_prewarm/autoprewarm.c
@@ -137,7 +137,7 @@ _PG_init(void)
 							 NULL,
 							 NULL);
 
-	EmitWarningsOnPlaceholders("pg_prewarm");
+	MarkGUCPrefixReserved("pg_prewarm");
 
 	RequestAddinShmemSpace(MAXALIGN(sizeof(AutoPrewarmSharedState)));
 
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 9d7d0812ac3..38d92a89cc4 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -437,7 +437,7 @@ _PG_init(void)
 							 NULL,
 							 NULL);
 
-	EmitWarningsOnPlaceholders("pg_stat_statements");
+	MarkGUCPrefixReserved("pg_stat_statements");
 
 	/*
 	 * Request additional shared resources.  (These are no-ops if we're not in
diff --git a/contrib/pg_trgm/trgm_op.c b/contrib/pg_trgm/trgm_op.c
index 0407c7dd644..e9b7981619f 100644
--- a/contrib/pg_trgm/trgm_op.c
+++ b/contrib/pg_trgm/trgm_op.c
@@ -101,7 +101,7 @@ _PG_init(void)
 							 NULL,
 							 NULL);
 
-	EmitWarningsOnPlaceholders("pg_trgm");
+	MarkGUCPrefixReserved("pg_trgm");
 }
 
 /*
diff --git a/contrib/postgres_fdw/option.c b/contrib/postgres_fdw/option.c
index af38e956e70..2c6b2894b96 100644
--- a/contrib/postgres_fdw/option.c
+++ b/contrib/postgres_fdw/option.c
@@ -538,5 +538,5 @@ _PG_init(void)
 							   NULL,
 							   NULL);
 
-	EmitWarningsOnPlaceholders("postgres_fdw");
+	MarkGUCPrefixReserved("postgres_fdw");
 }
diff --git a/contrib/sepgsql/hooks.c b/contrib/sepgsql/hooks.c
index d71c802106a..97e61b8043f 100644
--- a/contrib/sepgsql/hooks.c
+++ b/contrib/sepgsql/hooks.c
@@ -455,7 +455,7 @@ _PG_init(void)
 							 NULL,
 							 NULL);
 
-	EmitWarningsOnPlaceholders("sepgsql");
+	MarkGUCPrefixReserved("sepgsql");
 
 	/* Initialize userspace access vector cache */
 	sepgsql_avc_init();