/*----------------------------------------------------------------------

 *

 * tableamapi.c

 *    Support routines for API for Postgres table access methods

 *

 * Portions Copyright (c) 1996-2026, 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/tableam.h"

#include "access/xact.h"

#include "commands/defrem.h"

#include "miscadmin.h"

#include "utils/guc_hooks.h"

/*

 * GetTableAmRoutine

 *    Call the specified access method handler routine to get its

 *    TableAmRoutine struct, which we expect to be statically allocated.

 */

const TableAmRoutine *

GetTableAmRoutine(Oid amhandler)

{

  Datum   datum;

  const TableAmRoutine *routine;

  datum = OidFunctionCall0(amhandler);

  routine = (const 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_filelocator != 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);

  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;

}