Allow definition of lock mode for custom reloptions

Relation options can define a lock mode other than AccessExclusiveMode
since 47167b7, but modules defining custom relation options did not
really have a way to enforce that.  Correct that by extending the
current API set so as modules can define a custom lock mode.

Author: Michael Paquier
Reviewed-by: Kuntal Ghosh
Discussion: https://postgr.es/m/20190920013831.GD1844@paquier.xyz

contrib/bloom/blutils.c

@@ -60,7 +60,8 @@ _PG_init(void)
 	/* Option for length of signature */
 	add_int_reloption(bl_relopt_kind, "length",
 					  "Length of signature in bits",
-					  DEFAULT_BLOOM_LENGTH, 1, MAX_BLOOM_LENGTH);
+					  DEFAULT_BLOOM_LENGTH, 1, MAX_BLOOM_LENGTH,
+					  AccessExclusiveLock);
 	bl_relopt_tab[0].optname = "length";
 	bl_relopt_tab[0].opttype = RELOPT_TYPE_INT;
 	bl_relopt_tab[0].offset = offsetof(BloomOptions, bloomLength);
@@ -71,7 +72,8 @@ _PG_init(void)
 		snprintf(buf, sizeof(buf), "col%d", i + 1);
 		add_int_reloption(bl_relopt_kind, buf,
 						  "Number of bits generated for each index column",
-						  DEFAULT_BLOOM_BITS, 1, MAX_BLOOM_BITS);
+						  DEFAULT_BLOOM_BITS, 1, MAX_BLOOM_BITS,
+						  AccessExclusiveLock);
 		bl_relopt_tab[i + 1].optname = MemoryContextStrdup(TopMemoryContext,
 														   buf);
 		bl_relopt_tab[i + 1].opttype = RELOPT_TYPE_INT;

src/backend/access/common/reloptions.c

@@ -621,7 +621,8 @@ add_reloption(relopt_gen *newoption)
  *		(for types other than string)
  */
 static relopt_gen *
-allocate_reloption(bits32 kinds, int type, const char *name, const char *desc)
+allocate_reloption(bits32 kinds, int type, const char *name, const char *desc,
+				   LOCKMODE lockmode)
 {
 	MemoryContext oldcxt;
 	size_t		size;
@@ -658,13 +659,7 @@ allocate_reloption(bits32 kinds, int type, const char *name, const char *desc)
 	newoption->kinds = kinds;
 	newoption->namelen = strlen(name);
 	newoption->type = type;
-
-	/*
-	 * Set the default lock mode for this option.  There is no actual way
-	 * for a module to enforce it when declaring a custom relation option,
-	 * so just use the highest level, which is safe for all cases.
-	 */
-	newoption->lockmode = AccessExclusiveLock;
+	newoption->lockmode = lockmode;
 
 	MemoryContextSwitchTo(oldcxt);
 
@@ -676,12 +671,13 @@ allocate_reloption(bits32 kinds, int type, const char *name, const char *desc)
  *		Add a new boolean reloption
  */
 void
-add_bool_reloption(bits32 kinds, const char *name, const char *desc, bool default_val)
+add_bool_reloption(bits32 kinds, const char *name, const char *desc,
+				   bool default_val, LOCKMODE lockmode)
 {
 	relopt_bool *newoption;
 
 	newoption = (relopt_bool *) allocate_reloption(kinds, RELOPT_TYPE_BOOL,
-												   name, desc);
+												   name, desc, lockmode);
 	newoption->default_val = default_val;
 
 	add_reloption((relopt_gen *) newoption);
@@ -693,12 +689,12 @@ add_bool_reloption(bits32 kinds, const char *name, const char *desc, bool defaul
  */
 void
 add_int_reloption(bits32 kinds, const char *name, const char *desc, int default_val,
-				  int min_val, int max_val)
+				  int min_val, int max_val, LOCKMODE lockmode)
 {
 	relopt_int *newoption;
 
 	newoption = (relopt_int *) allocate_reloption(kinds, RELOPT_TYPE_INT,
-												  name, desc);
+												  name, desc, lockmode);
 	newoption->default_val = default_val;
 	newoption->min = min_val;
 	newoption->max = max_val;
@@ -712,12 +708,12 @@ add_int_reloption(bits32 kinds, const char *name, const char *desc, int default_
  */
 void
 add_real_reloption(bits32 kinds, const char *name, const char *desc, double default_val,
-				   double min_val, double max_val)
+				   double min_val, double max_val, LOCKMODE lockmode)
 {
 	relopt_real *newoption;
 
 	newoption = (relopt_real *) allocate_reloption(kinds, RELOPT_TYPE_REAL,
-												   name, desc);
+												   name, desc, lockmode);
 	newoption->default_val = default_val;
 	newoption->min = min_val;
 	newoption->max = max_val;
@@ -736,7 +732,7 @@ add_real_reloption(bits32 kinds, const char *name, const char *desc, double defa
  */
 void
 add_string_reloption(bits32 kinds, const char *name, const char *desc, const char *default_val,
-					 validate_string_relopt validator)
+					 validate_string_relopt validator, LOCKMODE lockmode)
 {
 	relopt_string *newoption;
 
@@ -745,7 +741,7 @@ add_string_reloption(bits32 kinds, const char *name, const char *desc, const cha
 		(validator) (default_val);
 
 	newoption = (relopt_string *) allocate_reloption(kinds, RELOPT_TYPE_STRING,
-													 name, desc);
+													 name, desc, lockmode);
 	newoption->validate_cb = validator;
 	if (default_val)
 	{

src/include/access/reloptions.h

@@ -247,13 +247,16 @@ typedef struct
 
 extern relopt_kind add_reloption_kind(void);
 extern void add_bool_reloption(bits32 kinds, const char *name, const char *desc,
-							   bool default_val);
+							   bool default_val, LOCKMODE lockmode);
 extern void add_int_reloption(bits32 kinds, const char *name, const char *desc,
-							  int default_val, int min_val, int max_val);
+							  int default_val, int min_val, int max_val,
+							  LOCKMODE lockmode);
 extern void add_real_reloption(bits32 kinds, const char *name, const char *desc,
-							   double default_val, double min_val, double max_val);
+							   double default_val, double min_val, double max_val,
+							   LOCKMODE lockmode);
 extern void add_string_reloption(bits32 kinds, const char *name, const char *desc,
-								 const char *default_val, validate_string_relopt validator);
+								 const char *default_val, validate_string_relopt validator,
+								 LOCKMODE lockmode);
 
 extern Datum transformRelOptions(Datum oldOptions, List *defList,
 								 const char *namspace, char *validnsps[],