Custom reloptions for table AM

Let table AM define custom reloptions for its tables.  This allows to
specify AM-specific parameters by WITH clause when creating a table.

The code may use some parts from prior work by Hao Wu.

Discussion: https://postgr.es/m/CAPpHfdurb9ycV8udYqM%3Do0sPS66PJ4RCBM1g-bBpvzUfogY0EA%40mail.gmail.com
Discussion: https://postgr.es/m/AMUA1wBBBxfc3tKRLLdU64rb.1.1683276279979.Hmail.wuhao%40hashdata.cn
Reviewed-by: Reviewed-by: Pavel Borisov, Matthias van de Meent

src/backend/access/common/reloptions.c

@@ -24,6 +24,7 @@
 #include "access/nbtree.h"
 #include "access/reloptions.h"
 #include "access/spgist_private.h"
+#include "access/tableam.h"
 #include "catalog/pg_type.h"
 #include "commands/defrem.h"
 #include "commands/tablespace.h"
@@ -1377,7 +1378,7 @@ untransformRelOptions(Datum options)
  */
 bytea *
 extractRelOptions(HeapTuple tuple, TupleDesc tupdesc,
-				  amoptions_function amoptions)
+				  const TableAmRoutine *tableam, amoptions_function amoptions)
 {
 	bytea	   *options;
 	bool		isnull;
@@ -1399,7 +1400,8 @@ extractRelOptions(HeapTuple tuple, TupleDesc tupdesc,
 		case RELKIND_RELATION:
 		case RELKIND_TOASTVALUE:
 		case RELKIND_MATVIEW:
-			options = heap_reloptions(classForm->relkind, datum, false);
+			options = tableam_reloptions(tableam, classForm->relkind,
+										 datum, false);
 			break;
 		case RELKIND_PARTITIONED_TABLE:
 			options = partitioned_table_reloptions(datum, false);

src/backend/access/heap/heapam_handler.c

@@ -23,6 +23,7 @@
 #include "access/heapam.h"
 #include "access/heaptoast.h"
 #include "access/multixact.h"
+#include "access/reloptions.h"
 #include "access/rewriteheap.h"
 #include "access/syncscan.h"
 #include "access/tableam.h"
@@ -2155,6 +2156,16 @@ heapam_relation_toast_am(Relation rel)
 	return rel->rd_rel->relam;
 }
 
+static bytea *
+heapam_reloptions(char relkind, Datum reloptions, bool validate)
+{
+	Assert(relkind == RELKIND_RELATION ||
+		   relkind == RELKIND_TOASTVALUE ||
+		   relkind == RELKIND_MATVIEW);
+
+	return heap_reloptions(relkind, reloptions, validate);
+}
+
 
 /* ------------------------------------------------------------------------
  * Planner related callbacks for the heap AM
@@ -2660,6 +2671,7 @@ static const TableAmRoutine heapam_methods = {
 	.relation_needs_toast_table = heapam_relation_needs_toast_table,
 	.relation_toast_am = heapam_relation_toast_am,
 	.relation_fetch_toast_slice = heap_fetch_toast_slice,
+	.reloptions = heapam_reloptions,
 
 	.relation_estimate_size = heapam_estimate_rel_size,
 

src/backend/access/table/tableamapi.c

@@ -13,9 +13,11 @@
 
 #include "access/tableam.h"
 #include "access/xact.h"
+#include "catalog/pg_am.h"
 #include "commands/defrem.h"
 #include "miscadmin.h"
 #include "utils/guc_hooks.h"
+#include "utils/syscache.h"
 
 
 /*
@@ -98,6 +100,29 @@ GetTableAmRoutine(Oid amhandler)
 	return routine;
 }
 
+/*
+ * GetTableAmRoutineByAmOid
+ *		Given the table access method oid get its TableAmRoutine struct, which
+ *		will be palloc'd in the caller's memory context.
+ */
+const TableAmRoutine *
+GetTableAmRoutineByAmOid(Oid amoid)
+{
+	HeapTuple	ht_am;
+	Form_pg_am	amrec;
+	const TableAmRoutine *tableam = NULL;
+
+	ht_am = SearchSysCache1(AMOID, ObjectIdGetDatum(amoid));
+	if (!HeapTupleIsValid(ht_am))
+		elog(ERROR, "cache lookup failed for access method %u",
+			 amoid);
+	amrec = (Form_pg_am) GETSTRUCT(ht_am);
+
+	tableam = GetTableAmRoutine(amrec->amhandler);
+	ReleaseSysCache(ht_am);
+	return tableam;
+}
+
 /* check_hook: validate new default_table_access_method */
 bool
 check_default_table_access_method(char **newval, void **extra, GucSource source)