1 files changed, 158 insertions, 0 deletions
diff --git a/src/backend/access/table/tableamapi.c b/src/backend/access/table/tableamapi.c
new file mode 100644
index 0000000..76df798
--- /dev/null
+++ b/src/backend/access/table/tableamapi.c
@@ -0,0 +1,158 @@
+/*----------------------------------------------------------------------
+ *
+ * tableamapi.c
+ *		Support routines for API for Postgres table access methods
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/backend/access/table/tableamapi.c
+ *----------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/heapam.h"
+#include "access/htup_details.h"
+#include "access/tableam.h"
+#include "access/xact.h"
+#include "catalog/pg_am.h"
+#include "catalog/pg_proc.h"
+#include "commands/defrem.h"
+#include "miscadmin.h"
+#include "utils/fmgroids.h"
+#include "utils/memutils.h"
+#include "utils/syscache.h"
+
+
+/*
+ * GetTableAmRoutine
+ *		Call the specified access method handler routine to get its
+ *		TableAmRoutine struct, which will be palloc'd in the caller's
+ *		memory context.
+ */
+const TableAmRoutine *
+GetTableAmRoutine(Oid amhandler)
+{
+	Datum		datum;
+	const TableAmRoutine *routine;
+
+	datum = OidFunctionCall0(amhandler);
+	routine = (TableAmRoutine *) DatumGetPointer(datum);
+
+	if (routine == NULL || !IsA(routine, TableAmRoutine))
+		elog(ERROR, "table access method handler %u did not return a TableAmRoutine struct",
+			 amhandler);
+
+	/*
+	 * Assert that all required callbacks are present. That makes it a bit
+	 * easier to keep AMs up to date, e.g. when forward porting them to a new
+	 * major version.
+	 */
+	Assert(routine->scan_begin != NULL);
+	Assert(routine->scan_end != NULL);
+	Assert(routine->scan_rescan != NULL);
+	Assert(routine->scan_getnextslot != NULL);
+
+	Assert(routine->parallelscan_estimate != NULL);
+	Assert(routine->parallelscan_initialize != NULL);
+	Assert(routine->parallelscan_reinitialize != NULL);
+
+	Assert(routine->index_fetch_begin != NULL);
+	Assert(routine->index_fetch_reset != NULL);
+	Assert(routine->index_fetch_end != NULL);
+	Assert(routine->index_fetch_tuple != NULL);
+
+	Assert(routine->tuple_fetch_row_version != NULL);
+	Assert(routine->tuple_tid_valid != NULL);
+	Assert(routine->tuple_get_latest_tid != NULL);
+	Assert(routine->tuple_satisfies_snapshot != NULL);
+	Assert(routine->index_delete_tuples != NULL);
+
+	Assert(routine->tuple_insert != NULL);
+
+	/*
+	 * Could be made optional, but would require throwing error during
+	 * parse-analysis.
+	 */
+	Assert(routine->tuple_insert_speculative != NULL);
+	Assert(routine->tuple_complete_speculative != NULL);
+
+	Assert(routine->multi_insert != NULL);
+	Assert(routine->tuple_delete != NULL);
+	Assert(routine->tuple_update != NULL);
+	Assert(routine->tuple_lock != NULL);
+
+	Assert(routine->relation_set_new_filenode != NULL);
+	Assert(routine->relation_nontransactional_truncate != NULL);
+	Assert(routine->relation_copy_data != NULL);
+	Assert(routine->relation_copy_for_cluster != NULL);
+	Assert(routine->relation_vacuum != NULL);
+	Assert(routine->scan_analyze_next_block != NULL);
+	Assert(routine->scan_analyze_next_tuple != NULL);
+	Assert(routine->index_build_range_scan != NULL);
+	Assert(routine->index_validate_scan != NULL);
+
+	Assert(routine->relation_size != NULL);
+	Assert(routine->relation_needs_toast_table != NULL);
+
+	Assert(routine->relation_estimate_size != NULL);
+
+	/* optional, but one callback implies presence of the other */
+	Assert((routine->scan_bitmap_next_block == NULL) ==
+		   (routine->scan_bitmap_next_tuple == NULL));
+	Assert(routine->scan_sample_next_block != NULL);
+	Assert(routine->scan_sample_next_tuple != NULL);
+
+	return routine;
+}
+
+/* check_hook: validate new default_table_access_method */
+bool
+check_default_table_access_method(char **newval, void **extra, GucSource source)
+{
+	if (**newval == '\0')
+	{
+		GUC_check_errdetail("%s cannot be empty.",
+							"default_table_access_method");
+		return false;
+	}
+
+	if (strlen(*newval) >= NAMEDATALEN)
+	{
+		GUC_check_errdetail("%s is too long (maximum %d characters).",
+							"default_table_access_method", NAMEDATALEN - 1);
+		return false;
+	}
+
+	/*
+	 * If we aren't inside a transaction, or not connected to a database, we
+	 * cannot do the catalog access necessary to verify the method.  Must
+	 * accept the value on faith.
+	 */
+	if (IsTransactionState() && MyDatabaseId != InvalidOid)
+	{
+		if (!OidIsValid(get_table_am_oid(*newval, true)))
+		{
+			/*
+			 * When source == PGC_S_TEST, don't throw a hard error for a
+			 * nonexistent table access method, only a NOTICE. See comments in
+			 * guc.h.
+			 */
+			if (source == PGC_S_TEST)
+			{
+				ereport(NOTICE,
+						(errcode(ERRCODE_UNDEFINED_OBJECT),
+						 errmsg("table access method \"%s\" does not exist",
+								*newval)));
+			}
+			else
+			{
+				GUC_check_errdetail("Table access method \"%s\" does not exist.",
+									*newval);
+				return false;
+			}
+		}
+	}
+
+	return true;
+}