Custom reloptions for table AM

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

The reloptions, which could be used outside of table AM, are now extracted
into the CommonRdOptions data structure.  These options could be by decision
of table AM directly specified by a user or calculated in some way.

The new test module test_tam_options evaluates the ability to set up custom
reloptions and calculate fields of CommonRdOptions on their base.

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, Jess Davis

src/include/access/reloptions.h

@@ -21,6 +21,7 @@
 
 #include "access/amapi.h"
 #include "access/htup.h"
+#include "access/tableam.h"
 #include "access/tupdesc.h"
 #include "nodes/pg_list.h"
 #include "storage/lock.h"
@@ -224,7 +225,9 @@ extern Datum transformRelOptions(Datum oldOptions, List *defList,
 								 bool acceptOidsOff, bool isReset);
 extern List *untransformRelOptions(Datum options);
 extern bytea *extractRelOptions(HeapTuple tuple, TupleDesc tupdesc,
-								amoptions_function amoptions);
+								const TableAmRoutine *tableam,
+								amoptions_function amoptions,
+								CommonRdOptions *common);
 extern void *build_reloptions(Datum reloptions, bool validate,
 							  relopt_kind kind,
 							  Size relopt_struct_size,
@@ -233,9 +236,8 @@ extern void *build_reloptions(Datum reloptions, bool validate,
 extern void *build_local_reloptions(local_relopts *relopts, Datum options,
 									bool validate);
 
-extern bytea *default_reloptions(Datum reloptions, bool validate,
-								 relopt_kind kind);
-extern bytea *heap_reloptions(char relkind, Datum reloptions, bool validate);
+extern bytea *heap_reloptions(char relkind, Datum reloptions,
+							  CommonRdOptions *common, bool validate);
 extern bytea *view_reloptions(Datum reloptions, bool validate);
 extern bytea *partitioned_table_reloptions(Datum reloptions, bool validate);
 extern bytea *index_reloptions(amoptions_function amoptions, Datum reloptions,

src/include/access/tableam.h

@@ -746,6 +746,34 @@ typedef struct TableAmRoutine
 											   int32 slicelength,
 											   struct varlena *result);
 
+	/*
+	 * This callback parses and validates the reloptions array for a table.
+	 *
+	 * This is called only when a non-null reloptions array exists for the
+	 * table.  'reloptions' is a text array containing entries of the form
+	 * "name=value".  The function should construct a bytea value, which will
+	 * be copied into the rd_options field of the table's relcache entry. The
+	 * data contents of the bytea value are open for the access method to
+	 * define.
+	 *
+	 * The '*common' represents the common values, which the table access
+	 * method exposes for autovacuum, query planner, and others.  The caller
+	 * should fill them with default values.  The table access method may
+	 * modify them on the base of options specified by a user.
+	 *
+	 * When 'validate' is true, the function should report a suitable error
+	 * message if any of the options are unrecognized or have invalid values;
+	 * when 'validate' is false, invalid entries should be silently ignored.
+	 * ('validate' is false when loading options already stored in pg_catalog;
+	 * an invalid entry could only be found if the access method has changed
+	 * its rules for options, and in that case ignoring obsolete entries is
+	 * appropriate.)
+	 *
+	 * It is OK to return NULL if default behavior is wanted.
+	 */
+	bytea	   *(*reloptions) (char relkind, Datum reloptions,
+							   CommonRdOptions *common, bool validate);
+
 
 	/* ------------------------------------------------------------------------
 	 * Planner related functions.
@@ -1945,6 +1973,27 @@ table_relation_fetch_toast_slice(Relation toastrel, Oid valueid,
 													 result);
 }
 
+/*
+ * Parse table options without knowledge of particular table.
+ */
+static inline bytea *
+tableam_reloptions(const TableAmRoutine *tableam, char relkind,
+				   Datum reloptions, CommonRdOptions *common, bool validate)
+{
+	return tableam->reloptions(relkind, reloptions, common, validate);
+}
+
+/*
+ * Parse options for given table.
+ */
+static inline bytea *
+table_reloptions(Relation rel, char relkind,
+				 Datum reloptions, CommonRdOptions *common, bool validate)
+{
+	return tableam_reloptions(rel->rd_tableam, relkind, reloptions,
+							  common, validate);
+}
+
 
 /* ----------------------------------------------------------------------------
  * Planner related functionality
@@ -2123,6 +2172,7 @@ extern void table_block_relation_estimate_size(Relation rel,
  */
 
 extern const TableAmRoutine *GetTableAmRoutine(Oid amhandler);
+extern const TableAmRoutine *GetTableAmRoutineByAmOid(Oid amoid);
 
 /* ----------------------------------------------------------------------------
  * Functions in heapam_handler.c