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

 *

 * pgstat_checkpointer.c

 *    Implementation of checkpoint statistics.

 *

 * This file contains the implementation of checkpoint statistics. It is kept

 * separate from pgstat.c to enforce the line between the statistics access /

 * storage implementation and the details about individual types of

 * statistics.

 *

 * Copyright (c) 2001-2025, PostgreSQL Global Development Group

 *

 * IDENTIFICATION

 *    src/backend/utils/activity/pgstat_checkpointer.c

 * -------------------------------------------------------------------------

 */

#include "postgres.h"

#include "utils/memutils.h"

#include "utils/pgstat_internal.h"

PgStat_CheckpointerStats PendingCheckpointerStats = {0};

/*

 * Report checkpointer and IO statistics

 */

void

pgstat_report_checkpointer(void)

{

  PgStatShared_Checkpointer *stats_shmem = &pgStatLocal.shmem->checkpointer;

  Assert(!pgStatLocal.shmem->is_shutdown);

  pgstat_assert_is_up();

  /*

   * This function can be called even if nothing at all has happened. In

   * this case, avoid unnecessarily modifying the stats entry.

   */

  if (pg_memory_is_all_zeros(&PendingCheckpointerStats,

                 sizeof(struct PgStat_CheckpointerStats)))

    return;

  pgstat_begin_changecount_write(&stats_shmem->changecount);

#define CHECKPOINTER_ACC(fld) stats_shmem->stats.fld += PendingCheckpointerStats.fld

  CHECKPOINTER_ACC(num_timed);

  CHECKPOINTER_ACC(num_requested);

  CHECKPOINTER_ACC(num_performed);

  CHECKPOINTER_ACC(restartpoints_timed);

  CHECKPOINTER_ACC(restartpoints_requested);

  CHECKPOINTER_ACC(restartpoints_performed);

  CHECKPOINTER_ACC(write_time);

  CHECKPOINTER_ACC(sync_time);

  CHECKPOINTER_ACC(buffers_written);

  CHECKPOINTER_ACC(slru_written);

#undef CHECKPOINTER_ACC

  pgstat_end_changecount_write(&stats_shmem->changecount);

  /*

   * Clear out the statistics buffer, so it can be re-used.

   */

  MemSet(&PendingCheckpointerStats, 0, sizeof(PendingCheckpointerStats));

  /*

   * Report IO statistics

   */

  pgstat_flush_io(false);

}

/*

 * pgstat_fetch_stat_checkpointer() -

 *

 * Support function for the SQL-callable pgstat* functions. Returns

 * a pointer to the checkpointer statistics struct.

 */

PgStat_CheckpointerStats *

pgstat_fetch_stat_checkpointer(void)

{

  pgstat_snapshot_fixed(PGSTAT_KIND_CHECKPOINTER);

  return &pgStatLocal.snapshot.checkpointer;

}

void

pgstat_checkpointer_init_shmem_cb(void *stats)

{

  PgStatShared_Checkpointer *stats_shmem = (PgStatShared_Checkpointer *) stats;

  LWLockInitialize(&stats_shmem->lock, LWTRANCHE_PGSTATS_DATA);

}

void

pgstat_checkpointer_reset_all_cb(TimestampTz ts)

{

  PgStatShared_Checkpointer *stats_shmem = &pgStatLocal.shmem->checkpointer;

  /* see explanation above PgStatShared_Checkpointer for the reset protocol */

  LWLockAcquire(&stats_shmem->lock, LW_EXCLUSIVE);

  pgstat_copy_changecounted_stats(&stats_shmem->reset_offset,

                  &stats_shmem->stats,

                  sizeof(stats_shmem->stats),

                  &stats_shmem->changecount);

  stats_shmem->stats.stat_reset_timestamp = ts;

  LWLockRelease(&stats_shmem->lock);

}

void

pgstat_checkpointer_snapshot_cb(void)

{

  PgStatShared_Checkpointer *stats_shmem = &pgStatLocal.shmem->checkpointer;

  PgStat_CheckpointerStats *reset_offset = &stats_shmem->reset_offset;

  PgStat_CheckpointerStats reset;

  pgstat_copy_changecounted_stats(&pgStatLocal.snapshot.checkpointer,

                  &stats_shmem->stats,

                  sizeof(stats_shmem->stats),

                  &stats_shmem->changecount);

  LWLockAcquire(&stats_shmem->lock, LW_SHARED);

  memcpy(&reset, reset_offset, sizeof(stats_shmem->stats));

  LWLockRelease(&stats_shmem->lock);

  /* compensate by reset offsets */

#define CHECKPOINTER_COMP(fld) pgStatLocal.snapshot.checkpointer.fld -= reset.fld;

  CHECKPOINTER_COMP(num_timed);

  CHECKPOINTER_COMP(num_requested);

  CHECKPOINTER_COMP(num_performed);

  CHECKPOINTER_COMP(restartpoints_timed);

  CHECKPOINTER_COMP(restartpoints_requested);

  CHECKPOINTER_COMP(restartpoints_performed);

  CHECKPOINTER_COMP(write_time);

  CHECKPOINTER_COMP(sync_time);

  CHECKPOINTER_COMP(buffers_written);

  CHECKPOINTER_COMP(slru_written);

#undef CHECKPOINTER_COMP

}