pgstat.h

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/* ----------
 *  pgstat.h
 *
 *  Definitions for the PostgreSQL statistics collector daemon.
 *
 *  Copyright (c) 2001-2021, PostgreSQL Global Development Group
 *
 *  src/include/pgstat.h
 * ----------
 */
#ifndef PGSTAT_H
#define PGSTAT_H

#include "datatype/timestamp.h"
#include "libpq/pqcomm.h"
#include "miscadmin.h"
#include "port/atomics.h"
#include "portability/instr_time.h"
#include "postmaster/pgarch.h"
#include "storage/proc.h"
#include "utils/hsearch.h"
#include "utils/relcache.h"


/* ----------
 * Paths for the statistics files (relative to installation's $PGDATA).
 * ----------
 */
#define PGSTAT_STAT_PERMANENT_DIRECTORY     "pg_stat"
#define PGSTAT_STAT_PERMANENT_FILENAME      "pg_stat/global.stat"
#define PGSTAT_STAT_PERMANENT_TMPFILE       "pg_stat/global.tmp"

/* Default directory to store temporary statistics data in */
#define PG_STAT_TMP_DIR     "pg_stat_tmp"

/* Values for track_functions GUC variable --- order is significant! */
typedef enum TrackFunctionsLevel
{
    TRACK_FUNC_OFF,
    TRACK_FUNC_PL,
    TRACK_FUNC_ALL
}           TrackFunctionsLevel;

/* Values to track the cause of session termination */
typedef enum SessionEndType
{
    DISCONNECT_NOT_YET,         /* still active */
    DISCONNECT_NORMAL,
    DISCONNECT_CLIENT_EOF,
    DISCONNECT_FATAL,
    DISCONNECT_KILLED
} SessionEndType;

/* ----------
 * The types of backend -> collector messages
 * ----------
 */
typedef enum StatMsgType
{
    PGSTAT_MTYPE_DUMMY,
    PGSTAT_MTYPE_INQUIRY,
    PGSTAT_MTYPE_TABSTAT,
    PGSTAT_MTYPE_TABPURGE,
    PGSTAT_MTYPE_DROPDB,
    PGSTAT_MTYPE_RESETCOUNTER,
    PGSTAT_MTYPE_RESETSHAREDCOUNTER,
    PGSTAT_MTYPE_RESETSINGLECOUNTER,
    PGSTAT_MTYPE_RESETSLRUCOUNTER,
    PGSTAT_MTYPE_RESETREPLSLOTCOUNTER,
    PGSTAT_MTYPE_AUTOVAC_START,
    PGSTAT_MTYPE_VACUUM,
    PGSTAT_MTYPE_ANALYZE,
    PGSTAT_MTYPE_ARCHIVER,
    PGSTAT_MTYPE_BGWRITER,
    PGSTAT_MTYPE_WAL,
    PGSTAT_MTYPE_SLRU,
    PGSTAT_MTYPE_FUNCSTAT,
    PGSTAT_MTYPE_FUNCPURGE,
    PGSTAT_MTYPE_RECOVERYCONFLICT,
    PGSTAT_MTYPE_TEMPFILE,
    PGSTAT_MTYPE_DEADLOCK,
    PGSTAT_MTYPE_CHECKSUMFAILURE,
    PGSTAT_MTYPE_REPLSLOT,
    PGSTAT_MTYPE_CONNECTION,
} StatMsgType;

/* ----------
 * The data type used for counters.
 * ----------
 */
typedef int64 PgStat_Counter;

/* ----------
 * PgStat_TableCounts           The actual per-table counts kept by a backend
 *
 * This struct should contain only actual event counters, because we memcmp
 * it against zeroes to detect whether there are any counts to transmit.
 * It is a component of PgStat_TableStatus (within-backend state) and
 * PgStat_TableEntry (the transmitted message format).
 *
 * Note: for a table, tuples_returned is the number of tuples successfully
 * fetched by heap_getnext, while tuples_fetched is the number of tuples
 * successfully fetched by heap_fetch under the control of bitmap indexscans.
 * For an index, tuples_returned is the number of index entries returned by
 * the index AM, while tuples_fetched is the number of tuples successfully
 * fetched by heap_fetch under the control of simple indexscans for this index.
 *
 * tuples_inserted/updated/deleted/hot_updated count attempted actions,
 * regardless of whether the transaction committed.  delta_live_tuples,
 * delta_dead_tuples, and changed_tuples are set depending on commit or abort.
 * Note that delta_live_tuples and delta_dead_tuples can be negative!
 * ----------
 */
typedef struct PgStat_TableCounts
{
    PgStat_Counter t_numscans;

    PgStat_Counter t_tuples_returned;
    PgStat_Counter t_tuples_fetched;

    PgStat_Counter t_tuples_inserted;
    PgStat_Counter t_tuples_updated;
    PgStat_Counter t_tuples_deleted;
    PgStat_Counter t_tuples_hot_updated;
    bool        t_truncated;

    PgStat_Counter t_delta_live_tuples;
    PgStat_Counter t_delta_dead_tuples;
    PgStat_Counter t_changed_tuples;

    PgStat_Counter t_blocks_fetched;
    PgStat_Counter t_blocks_hit;
} PgStat_TableCounts;

/* Possible targets for resetting cluster-wide shared values */
typedef enum PgStat_Shared_Reset_Target
{
    RESET_ARCHIVER,
    RESET_BGWRITER,
    RESET_WAL
} PgStat_Shared_Reset_Target;

/* Possible object types for resetting single counters */
typedef enum PgStat_Single_Reset_Type
{
    RESET_TABLE,
    RESET_FUNCTION
} PgStat_Single_Reset_Type;

/* ------------------------------------------------------------
 * Structures kept in backend local memory while accumulating counts
 * ------------------------------------------------------------
 */


/* ----------
 * PgStat_TableStatus           Per-table status within a backend
 *
 * Many of the event counters are nontransactional, ie, we count events
 * in committed and aborted transactions alike.  For these, we just count
 * directly in the PgStat_TableStatus.  However, delta_live_tuples,
 * delta_dead_tuples, and changed_tuples must be derived from event counts
 * with awareness of whether the transaction or subtransaction committed or
 * aborted.  Hence, we also keep a stack of per-(sub)transaction status
 * records for every table modified in the current transaction.  At commit
 * or abort, we propagate tuples_inserted/updated/deleted up to the
 * parent subtransaction level, or out to the parent PgStat_TableStatus,
 * as appropriate.
 * ----------
 */
typedef struct PgStat_TableStatus
{
    Oid         t_id;           /* table's OID */
    bool        t_shared;       /* is it a shared catalog? */
    struct PgStat_TableXactStatus *trans;   /* lowest subxact's counts */
    PgStat_TableCounts t_counts;    /* event counts to be sent */
} PgStat_TableStatus;

/* ----------
 * PgStat_TableXactStatus       Per-table, per-subtransaction status
 * ----------
 */
typedef struct PgStat_TableXactStatus
{
    PgStat_Counter tuples_inserted; /* tuples inserted in (sub)xact */
    PgStat_Counter tuples_updated;  /* tuples updated in (sub)xact */
    PgStat_Counter tuples_deleted;  /* tuples deleted in (sub)xact */
    bool        truncated;      /* relation truncated in this (sub)xact */
    PgStat_Counter inserted_pre_trunc;  /* tuples inserted prior to truncate */
    PgStat_Counter updated_pre_trunc;   /* tuples updated prior to truncate */
    PgStat_Counter deleted_pre_trunc;   /* tuples deleted prior to truncate */
    int         nest_level;     /* subtransaction nest level */
    /* links to other structs for same relation: */
    struct PgStat_TableXactStatus *upper;   /* next higher subxact if any */
    PgStat_TableStatus *parent; /* per-table status */
    /* structs of same subxact level are linked here: */
    struct PgStat_TableXactStatus *next;    /* next of same subxact */
} PgStat_TableXactStatus;


/* ------------------------------------------------------------
 * Message formats follow
 * ------------------------------------------------------------
 */


/* ----------
 * PgStat_MsgHdr                The common message header
 * ----------
 */
typedef struct PgStat_MsgHdr
{
    StatMsgType m_type;
    int         m_size;
} PgStat_MsgHdr;

/* ----------
 * Space available in a message.  This will keep the UDP packets below 1K,
 * which should fit unfragmented into the MTU of the loopback interface.
 * (Larger values of PGSTAT_MAX_MSG_SIZE would work for that on most
 * platforms, but we're being conservative here.)
 * ----------
 */
#define PGSTAT_MAX_MSG_SIZE 1000
#define PGSTAT_MSG_PAYLOAD  (PGSTAT_MAX_MSG_SIZE - sizeof(PgStat_MsgHdr))


/* ----------
 * PgStat_MsgDummy              A dummy message, ignored by the collector
 * ----------
 */
typedef struct PgStat_MsgDummy
{
    PgStat_MsgHdr m_hdr;
} PgStat_MsgDummy;


/* ----------
 * PgStat_MsgInquiry            Sent by a backend to ask the collector
 *                              to write the stats file(s).
 *
 * Ordinarily, an inquiry message prompts writing of the global stats file,
 * the stats file for shared catalogs, and the stats file for the specified
 * database.  If databaseid is InvalidOid, only the first two are written.
 *
 * New file(s) will be written only if the existing file has a timestamp
 * older than the specified cutoff_time; this prevents duplicated effort
 * when multiple requests arrive at nearly the same time, assuming that
 * backends send requests with cutoff_times a little bit in the past.
 *
 * clock_time should be the requestor's current local time; the collector
 * uses this to check for the system clock going backward, but it has no
 * effect unless that occurs.  We assume clock_time >= cutoff_time, though.
 * ----------
 */

typedef struct PgStat_MsgInquiry
{
    PgStat_MsgHdr m_hdr;
    TimestampTz clock_time;     /* observed local clock time */
    TimestampTz cutoff_time;    /* minimum acceptable file timestamp */
    Oid         databaseid;     /* requested DB (InvalidOid => shared only) */
} PgStat_MsgInquiry;


/* ----------
 * PgStat_TableEntry            Per-table info in a MsgTabstat
 * ----------
 */
typedef struct PgStat_TableEntry
{
    Oid         t_id;
    PgStat_TableCounts t_counts;
} PgStat_TableEntry;

/* ----------
 * PgStat_MsgTabstat            Sent by the backend to report table
 *                              and buffer access statistics.
 * ----------
 */
#define PGSTAT_NUM_TABENTRIES  \
    ((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - 3 * sizeof(int) - 2 * sizeof(PgStat_Counter))  \
     / sizeof(PgStat_TableEntry))

typedef struct PgStat_MsgTabstat
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
    int         m_nentries;
    int         m_xact_commit;
    int         m_xact_rollback;
    PgStat_Counter m_block_read_time;   /* times in microseconds */
    PgStat_Counter m_block_write_time;
    PgStat_TableEntry m_entry[PGSTAT_NUM_TABENTRIES];
} PgStat_MsgTabstat;


/* ----------
 * PgStat_MsgTabpurge           Sent by the backend to tell the collector
 *                              about dead tables.
 * ----------
 */
#define PGSTAT_NUM_TABPURGE  \
    ((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - sizeof(int))  \
     / sizeof(Oid))

typedef struct PgStat_MsgTabpurge
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
    int         m_nentries;
    Oid         m_tableid[PGSTAT_NUM_TABPURGE];
} PgStat_MsgTabpurge;


/* ----------
 * PgStat_MsgDropdb             Sent by the backend to tell the collector
 *                              about a dropped database
 * ----------
 */
typedef struct PgStat_MsgDropdb
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
} PgStat_MsgDropdb;


/* ----------
 * PgStat_MsgResetcounter       Sent by the backend to tell the collector
 *                              to reset counters
 * ----------
 */
typedef struct PgStat_MsgResetcounter
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
} PgStat_MsgResetcounter;

/* ----------
 * PgStat_MsgResetsharedcounter Sent by the backend to tell the collector
 *                              to reset a shared counter
 * ----------
 */
typedef struct PgStat_MsgResetsharedcounter
{
    PgStat_MsgHdr m_hdr;
    PgStat_Shared_Reset_Target m_resettarget;
} PgStat_MsgResetsharedcounter;

/* ----------
 * PgStat_MsgResetsinglecounter Sent by the backend to tell the collector
 *                              to reset a single counter
 * ----------
 */
typedef struct PgStat_MsgResetsinglecounter
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
    PgStat_Single_Reset_Type m_resettype;
    Oid         m_objectid;
} PgStat_MsgResetsinglecounter;

/* ----------
 * PgStat_MsgResetslrucounter Sent by the backend to tell the collector
 *                              to reset a SLRU counter
 * ----------
 */
typedef struct PgStat_MsgResetslrucounter
{
    PgStat_MsgHdr m_hdr;
    int         m_index;
} PgStat_MsgResetslrucounter;

/* ----------
 * PgStat_MsgResetreplslotcounter Sent by the backend to tell the collector
 *                              to reset replication slot counter(s)
 * ----------
 */
typedef struct PgStat_MsgResetreplslotcounter
{
    PgStat_MsgHdr m_hdr;
    char        m_slotname[NAMEDATALEN];
    bool        clearall;
} PgStat_MsgResetreplslotcounter;

/* ----------
 * PgStat_MsgAutovacStart       Sent by the autovacuum daemon to signal
 *                              that a database is going to be processed
 * ----------
 */
typedef struct PgStat_MsgAutovacStart
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
    TimestampTz m_start_time;
} PgStat_MsgAutovacStart;


/* ----------
 * PgStat_MsgVacuum             Sent by the backend or autovacuum daemon
 *                              after VACUUM
 * ----------
 */
typedef struct PgStat_MsgVacuum
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
    Oid         m_tableoid;
    bool        m_autovacuum;
    TimestampTz m_vacuumtime;
    PgStat_Counter m_live_tuples;
    PgStat_Counter m_dead_tuples;
} PgStat_MsgVacuum;


/* ----------
 * PgStat_MsgAnalyze            Sent by the backend or autovacuum daemon
 *                              after ANALYZE
 * ----------
 */
typedef struct PgStat_MsgAnalyze
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
    Oid         m_tableoid;
    bool        m_autovacuum;
    bool        m_resetcounter;
    TimestampTz m_analyzetime;
    PgStat_Counter m_live_tuples;
    PgStat_Counter m_dead_tuples;
} PgStat_MsgAnalyze;


/* ----------
 * PgStat_MsgArchiver           Sent by the archiver to update statistics.
 * ----------
 */
typedef struct PgStat_MsgArchiver
{
    PgStat_MsgHdr m_hdr;
    bool        m_failed;       /* Failed attempt */
    char        m_xlog[MAX_XFN_CHARS + 1];
    TimestampTz m_timestamp;
} PgStat_MsgArchiver;

/* ----------
 * PgStat_MsgBgWriter           Sent by the bgwriter to update statistics.
 * ----------
 */
typedef struct PgStat_MsgBgWriter
{
    PgStat_MsgHdr m_hdr;

    PgStat_Counter m_timed_checkpoints;
    PgStat_Counter m_requested_checkpoints;
    PgStat_Counter m_buf_written_checkpoints;
    PgStat_Counter m_buf_written_clean;
    PgStat_Counter m_maxwritten_clean;
    PgStat_Counter m_buf_written_backend;
    PgStat_Counter m_buf_fsync_backend;
    PgStat_Counter m_buf_alloc;
    PgStat_Counter m_checkpoint_write_time; /* times in milliseconds */
    PgStat_Counter m_checkpoint_sync_time;
} PgStat_MsgBgWriter;

/* ----------
 * PgStat_MsgWal            Sent by backends and background processes to update WAL statistics.
 * ----------
 */
typedef struct PgStat_MsgWal
{
    PgStat_MsgHdr m_hdr;
    PgStat_Counter m_wal_records;
    PgStat_Counter m_wal_fpi;
    uint64      m_wal_bytes;
    PgStat_Counter m_wal_buffers_full;
} PgStat_MsgWal;

/* ----------
 * PgStat_MsgSLRU           Sent by a backend to update SLRU statistics.
 * ----------
 */
typedef struct PgStat_MsgSLRU
{
    PgStat_MsgHdr m_hdr;
    PgStat_Counter m_index;
    PgStat_Counter m_blocks_zeroed;
    PgStat_Counter m_blocks_hit;
    PgStat_Counter m_blocks_read;
    PgStat_Counter m_blocks_written;
    PgStat_Counter m_blocks_exists;
    PgStat_Counter m_flush;
    PgStat_Counter m_truncate;
} PgStat_MsgSLRU;

/* ----------
 * PgStat_MsgReplSlot   Sent by a backend or a wal sender to update replication
 *                      slot statistics.
 * ----------
 */
typedef struct PgStat_MsgReplSlot
{
    PgStat_MsgHdr m_hdr;
    char        m_slotname[NAMEDATALEN];
    bool        m_drop;
    PgStat_Counter m_spill_txns;
    PgStat_Counter m_spill_count;
    PgStat_Counter m_spill_bytes;
    PgStat_Counter m_stream_txns;
    PgStat_Counter m_stream_count;
    PgStat_Counter m_stream_bytes;
} PgStat_MsgReplSlot;


/* ----------
 * PgStat_MsgRecoveryConflict   Sent by the backend upon recovery conflict
 * ----------
 */
typedef struct PgStat_MsgRecoveryConflict
{
    PgStat_MsgHdr m_hdr;

    Oid         m_databaseid;
    int         m_reason;
} PgStat_MsgRecoveryConflict;

/* ----------
 * PgStat_MsgTempFile   Sent by the backend upon creating a temp file
 * ----------
 */
typedef struct PgStat_MsgTempFile
{
    PgStat_MsgHdr m_hdr;

    Oid         m_databaseid;
    size_t      m_filesize;
} PgStat_MsgTempFile;

/* ----------
 * PgStat_FunctionCounts    The actual per-function counts kept by a backend
 *
 * This struct should contain only actual event counters, because we memcmp
 * it against zeroes to detect whether there are any counts to transmit.
 *
 * Note that the time counters are in instr_time format here.  We convert to
 * microseconds in PgStat_Counter format when transmitting to the collector.
 * ----------
 */
typedef struct PgStat_FunctionCounts
{
    PgStat_Counter f_numcalls;
    instr_time  f_total_time;
    instr_time  f_self_time;
} PgStat_FunctionCounts;

/* ----------
 * PgStat_BackendFunctionEntry  Entry in backend's per-function hash table
 * ----------
 */
typedef struct PgStat_BackendFunctionEntry
{
    Oid         f_id;
    PgStat_FunctionCounts f_counts;
} PgStat_BackendFunctionEntry;

/* ----------
 * PgStat_FunctionEntry         Per-function info in a MsgFuncstat
 * ----------
 */
typedef struct PgStat_FunctionEntry
{
    Oid         f_id;
    PgStat_Counter f_numcalls;
    PgStat_Counter f_total_time;    /* times in microseconds */
    PgStat_Counter f_self_time;
} PgStat_FunctionEntry;

/* ----------
 * PgStat_MsgFuncstat           Sent by the backend to report function
 *                              usage statistics.
 * ----------
 */
#define PGSTAT_NUM_FUNCENTRIES  \
    ((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - sizeof(int))  \
     / sizeof(PgStat_FunctionEntry))

typedef struct PgStat_MsgFuncstat
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
    int         m_nentries;
    PgStat_FunctionEntry m_entry[PGSTAT_NUM_FUNCENTRIES];
} PgStat_MsgFuncstat;

/* ----------
 * PgStat_MsgFuncpurge          Sent by the backend to tell the collector
 *                              about dead functions.
 * ----------
 */
#define PGSTAT_NUM_FUNCPURGE  \
    ((PGSTAT_MSG_PAYLOAD - sizeof(Oid) - sizeof(int))  \
     / sizeof(Oid))

typedef struct PgStat_MsgFuncpurge
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
    int         m_nentries;
    Oid         m_functionid[PGSTAT_NUM_FUNCPURGE];
} PgStat_MsgFuncpurge;

/* ----------
 * PgStat_MsgDeadlock           Sent by the backend to tell the collector
 *                              about a deadlock that occurred.
 * ----------
 */
typedef struct PgStat_MsgDeadlock
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
} PgStat_MsgDeadlock;

/* ----------
 * PgStat_MsgChecksumFailure    Sent by the backend to tell the collector
 *                              about checksum failures noticed.
 * ----------
 */
typedef struct PgStat_MsgChecksumFailure
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
    int         m_failurecount;
    TimestampTz m_failure_time;
} PgStat_MsgChecksumFailure;

/* ----------
 * PgStat_MsgConn           Sent by the backend to update connection statistics.
 * ----------
 */
typedef struct PgStat_MsgConn
{
    PgStat_MsgHdr m_hdr;
    Oid         m_databaseid;
    PgStat_Counter m_count;
    PgStat_Counter m_session_time;
    PgStat_Counter m_active_time;
    PgStat_Counter m_idle_in_xact_time;
    SessionEndType m_disconnect;
} PgStat_MsgConn;


/* ----------
 * PgStat_Msg                   Union over all possible messages.
 * ----------
 */
typedef union PgStat_Msg
{
    PgStat_MsgHdr msg_hdr;
    PgStat_MsgDummy msg_dummy;
    PgStat_MsgInquiry msg_inquiry;
    PgStat_MsgTabstat msg_tabstat;
    PgStat_MsgTabpurge msg_tabpurge;
    PgStat_MsgDropdb msg_dropdb;
    PgStat_MsgResetcounter msg_resetcounter;
    PgStat_MsgResetsharedcounter msg_resetsharedcounter;
    PgStat_MsgResetsinglecounter msg_resetsinglecounter;
    PgStat_MsgResetslrucounter msg_resetslrucounter;
    PgStat_MsgResetreplslotcounter msg_resetreplslotcounter;
    PgStat_MsgAutovacStart msg_autovacuum_start;
    PgStat_MsgVacuum msg_vacuum;
    PgStat_MsgAnalyze msg_analyze;
    PgStat_MsgArchiver msg_archiver;
    PgStat_MsgBgWriter msg_bgwriter;
    PgStat_MsgWal msg_wal;
    PgStat_MsgSLRU msg_slru;
    PgStat_MsgFuncstat msg_funcstat;
    PgStat_MsgFuncpurge msg_funcpurge;
    PgStat_MsgRecoveryConflict msg_recoveryconflict;
    PgStat_MsgDeadlock msg_deadlock;
    PgStat_MsgTempFile msg_tempfile;
    PgStat_MsgChecksumFailure msg_checksumfailure;
    PgStat_MsgReplSlot msg_replslot;
    PgStat_MsgConn msg_conn;
} PgStat_Msg;


/* ------------------------------------------------------------
 * Statistic collector data structures follow
 *
 * PGSTAT_FILE_FORMAT_ID should be changed whenever any of these
 * data structures change.
 * ------------------------------------------------------------
 */

#define PGSTAT_FILE_FORMAT_ID   0x01A5BCA0

/* ----------
 * PgStat_StatDBEntry           The collector's data per database
 * ----------
 */
typedef struct PgStat_StatDBEntry
{
    Oid         databaseid;
    PgStat_Counter n_xact_commit;
    PgStat_Counter n_xact_rollback;
    PgStat_Counter n_blocks_fetched;
    PgStat_Counter n_blocks_hit;
    PgStat_Counter n_tuples_returned;
    PgStat_Counter n_tuples_fetched;
    PgStat_Counter n_tuples_inserted;
    PgStat_Counter n_tuples_updated;
    PgStat_Counter n_tuples_deleted;
    TimestampTz last_autovac_time;
    PgStat_Counter n_conflict_tablespace;
    PgStat_Counter n_conflict_lock;
    PgStat_Counter n_conflict_snapshot;
    PgStat_Counter n_conflict_bufferpin;
    PgStat_Counter n_conflict_startup_deadlock;
    PgStat_Counter n_temp_files;
    PgStat_Counter n_temp_bytes;
    PgStat_Counter n_deadlocks;
    PgStat_Counter n_checksum_failures;
    TimestampTz last_checksum_failure;
    PgStat_Counter n_block_read_time;   /* times in microseconds */
    PgStat_Counter n_block_write_time;
    PgStat_Counter n_sessions;
    PgStat_Counter total_session_time;
    PgStat_Counter total_active_time;
    PgStat_Counter total_idle_in_xact_time;
    PgStat_Counter n_sessions_abandoned;
    PgStat_Counter n_sessions_fatal;
    PgStat_Counter n_sessions_killed;

    TimestampTz stat_reset_timestamp;
    TimestampTz stats_timestamp;    /* time of db stats file update */

    /*
     * tables and functions must be last in the struct, because we don't write
     * the pointers out to the stats file.
     */
    HTAB       *tables;
    HTAB       *functions;
} PgStat_StatDBEntry;


/* ----------
 * PgStat_StatTabEntry          The collector's data per table (or index)
 * ----------
 */
typedef struct PgStat_StatTabEntry
{
    Oid         tableid;

    PgStat_Counter numscans;

    PgStat_Counter tuples_returned;
    PgStat_Counter tuples_fetched;

    PgStat_Counter tuples_inserted;
    PgStat_Counter tuples_updated;
    PgStat_Counter tuples_deleted;
    PgStat_Counter tuples_hot_updated;

    PgStat_Counter n_live_tuples;
    PgStat_Counter n_dead_tuples;
    PgStat_Counter changes_since_analyze;
    PgStat_Counter inserts_since_vacuum;

    PgStat_Counter blocks_fetched;
    PgStat_Counter blocks_hit;

    TimestampTz vacuum_timestamp;   /* user initiated vacuum */
    PgStat_Counter vacuum_count;
    TimestampTz autovac_vacuum_timestamp;   /* autovacuum initiated */
    PgStat_Counter autovac_vacuum_count;
    TimestampTz analyze_timestamp;  /* user initiated */
    PgStat_Counter analyze_count;
    TimestampTz autovac_analyze_timestamp;  /* autovacuum initiated */
    PgStat_Counter autovac_analyze_count;
} PgStat_StatTabEntry;


/* ----------
 * PgStat_StatFuncEntry         The collector's data per function
 * ----------
 */
typedef struct PgStat_StatFuncEntry
{
    Oid         functionid;

    PgStat_Counter f_numcalls;

    PgStat_Counter f_total_time;    /* times in microseconds */
    PgStat_Counter f_self_time;
} PgStat_StatFuncEntry;


/*
 * Archiver statistics kept in the stats collector
 */
typedef struct PgStat_ArchiverStats
{
    PgStat_Counter archived_count;  /* archival successes */
    char        last_archived_wal[MAX_XFN_CHARS + 1];   /* last WAL file
                                                         * archived */
    TimestampTz last_archived_timestamp;    /* last archival success time */
    PgStat_Counter failed_count;    /* failed archival attempts */
    char        last_failed_wal[MAX_XFN_CHARS + 1]; /* WAL file involved in
                                                     * last failure */
    TimestampTz last_failed_timestamp;  /* last archival failure time */
    TimestampTz stat_reset_timestamp;
} PgStat_ArchiverStats;

/*
 * Global statistics kept in the stats collector
 */
typedef struct PgStat_GlobalStats
{
    TimestampTz stats_timestamp;    /* time of stats file update */
    PgStat_Counter timed_checkpoints;
    PgStat_Counter requested_checkpoints;
    PgStat_Counter checkpoint_write_time;   /* times in milliseconds */
    PgStat_Counter checkpoint_sync_time;
    PgStat_Counter buf_written_checkpoints;
    PgStat_Counter buf_written_clean;
    PgStat_Counter maxwritten_clean;
    PgStat_Counter buf_written_backend;
    PgStat_Counter buf_fsync_backend;
    PgStat_Counter buf_alloc;
    TimestampTz stat_reset_timestamp;
} PgStat_GlobalStats;

/*
 * WAL statistics kept in the stats collector
 */
typedef struct PgStat_WalStats
{
    PgStat_Counter wal_records;
    PgStat_Counter wal_fpi;
    uint64      wal_bytes;
    PgStat_Counter wal_buffers_full;
    TimestampTz stat_reset_timestamp;
} PgStat_WalStats;

/*
 * SLRU statistics kept in the stats collector
 */
typedef struct PgStat_SLRUStats
{
    PgStat_Counter blocks_zeroed;
    PgStat_Counter blocks_hit;
    PgStat_Counter blocks_read;
    PgStat_Counter blocks_written;
    PgStat_Counter blocks_exists;
    PgStat_Counter flush;
    PgStat_Counter truncate;
    TimestampTz stat_reset_timestamp;
} PgStat_SLRUStats;

/*
 * Replication slot statistics kept in the stats collector
 */
typedef struct PgStat_ReplSlotStats
{
    char        slotname[NAMEDATALEN];
    PgStat_Counter spill_txns;
    PgStat_Counter spill_count;
    PgStat_Counter spill_bytes;
    PgStat_Counter stream_txns;
    PgStat_Counter stream_count;
    PgStat_Counter stream_bytes;
    TimestampTz stat_reset_timestamp;
} PgStat_ReplSlotStats;

/* ----------
 * Backend states
 * ----------
 */
typedef enum BackendState
{
    STATE_UNDEFINED,
    STATE_IDLE,
    STATE_RUNNING,
    STATE_IDLEINTRANSACTION,
    STATE_FASTPATH,
    STATE_IDLEINTRANSACTION_ABORTED,
    STATE_DISABLED
} BackendState;


/* ----------
 * Wait Classes
 * ----------
 */
#define PG_WAIT_LWLOCK              0x01000000U
#define PG_WAIT_LOCK                0x03000000U
#define PG_WAIT_BUFFER_PIN          0x04000000U
#define PG_WAIT_ACTIVITY            0x05000000U
#define PG_WAIT_CLIENT              0x06000000U
#define PG_WAIT_EXTENSION           0x07000000U
#define PG_WAIT_IPC                 0x08000000U
#define PG_WAIT_TIMEOUT             0x09000000U
#define PG_WAIT_IO                  0x0A000000U

/* ----------
 * Wait Events - Activity
 *
 * Use this category when a process is waiting because it has no work to do,
 * unless the "Client" or "Timeout" category describes the situation better.
 * Typically, this should only be used for background processes.
 * ----------
 */
typedef enum
{
    WAIT_EVENT_ARCHIVER_MAIN = PG_WAIT_ACTIVITY,
    WAIT_EVENT_AUTOVACUUM_MAIN,
    WAIT_EVENT_BGWRITER_HIBERNATE,
    WAIT_EVENT_BGWRITER_MAIN,
    WAIT_EVENT_CHECKPOINTER_MAIN,
    WAIT_EVENT_LOGICAL_APPLY_MAIN,
    WAIT_EVENT_LOGICAL_LAUNCHER_MAIN,
    WAIT_EVENT_PGSTAT_MAIN,
    WAIT_EVENT_RECOVERY_WAL_STREAM,
    WAIT_EVENT_SYSLOGGER_MAIN,
    WAIT_EVENT_WAL_RECEIVER_MAIN,
    WAIT_EVENT_WAL_SENDER_MAIN,
    WAIT_EVENT_WAL_WRITER_MAIN
} WaitEventActivity;

/* ----------
 * Wait Events - Client
 *
 * Use this category when a process is waiting to send data to or receive data
 * from the frontend process to which it is connected.  This is never used for
 * a background process, which has no client connection.
 * ----------
 */
typedef enum
{
    WAIT_EVENT_CLIENT_READ = PG_WAIT_CLIENT,
    WAIT_EVENT_CLIENT_WRITE,
    WAIT_EVENT_GSS_OPEN_SERVER,
    WAIT_EVENT_LIBPQWALRECEIVER_CONNECT,
    WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE,
    WAIT_EVENT_SSL_OPEN_SERVER,
    WAIT_EVENT_WAL_RECEIVER_WAIT_START,
    WAIT_EVENT_WAL_SENDER_WAIT_WAL,
    WAIT_EVENT_WAL_SENDER_WRITE_DATA,
} WaitEventClient;

/* ----------
 * Wait Events - IPC
 *
 * Use this category when a process cannot complete the work it is doing because
 * it is waiting for a notification from another process.
 * ----------
 */
typedef enum
{
    WAIT_EVENT_BACKUP_WAIT_WAL_ARCHIVE = PG_WAIT_IPC,
    WAIT_EVENT_BGWORKER_SHUTDOWN,
    WAIT_EVENT_BGWORKER_STARTUP,
    WAIT_EVENT_BTREE_PAGE,
    WAIT_EVENT_CHECKPOINT_DONE,
    WAIT_EVENT_CHECKPOINT_START,
    WAIT_EVENT_EXECUTE_GATHER,
    WAIT_EVENT_HASH_BATCH_ALLOCATE,
    WAIT_EVENT_HASH_BATCH_ELECT,
    WAIT_EVENT_HASH_BATCH_LOAD,
    WAIT_EVENT_HASH_BUILD_ALLOCATE,
    WAIT_EVENT_HASH_BUILD_ELECT,
    WAIT_EVENT_HASH_BUILD_HASH_INNER,
    WAIT_EVENT_HASH_BUILD_HASH_OUTER,
    WAIT_EVENT_HASH_GROW_BATCHES_ALLOCATE,
    WAIT_EVENT_HASH_GROW_BATCHES_DECIDE,
    WAIT_EVENT_HASH_GROW_BATCHES_ELECT,
    WAIT_EVENT_HASH_GROW_BATCHES_FINISH,
    WAIT_EVENT_HASH_GROW_BATCHES_REPARTITION,
    WAIT_EVENT_HASH_GROW_BUCKETS_ALLOCATE,
    WAIT_EVENT_HASH_GROW_BUCKETS_ELECT,
    WAIT_EVENT_HASH_GROW_BUCKETS_REINSERT,
    WAIT_EVENT_LOGICAL_SYNC_DATA,
    WAIT_EVENT_LOGICAL_SYNC_STATE_CHANGE,
    WAIT_EVENT_MQ_INTERNAL,
    WAIT_EVENT_MQ_PUT_MESSAGE,
    WAIT_EVENT_MQ_RECEIVE,
    WAIT_EVENT_MQ_SEND,
    WAIT_EVENT_PARALLEL_BITMAP_SCAN,
    WAIT_EVENT_PARALLEL_CREATE_INDEX_SCAN,
    WAIT_EVENT_PARALLEL_FINISH,
    WAIT_EVENT_PROCARRAY_GROUP_UPDATE,
    WAIT_EVENT_PROC_SIGNAL_BARRIER,
    WAIT_EVENT_PROMOTE,
    WAIT_EVENT_RECOVERY_CONFLICT_SNAPSHOT,
    WAIT_EVENT_RECOVERY_CONFLICT_TABLESPACE,
    WAIT_EVENT_RECOVERY_PAUSE,
    WAIT_EVENT_REPLICATION_ORIGIN_DROP,
    WAIT_EVENT_REPLICATION_SLOT_DROP,
    WAIT_EVENT_SAFE_SNAPSHOT,
    WAIT_EVENT_SYNC_REP,
    WAIT_EVENT_XACT_GROUP_UPDATE
} WaitEventIPC;

/* ----------
 * Wait Events - Timeout
 *
 * Use this category when a process is waiting for a timeout to expire.
 * ----------
 */
typedef enum
{
    WAIT_EVENT_BASE_BACKUP_THROTTLE = PG_WAIT_TIMEOUT,
    WAIT_EVENT_PG_SLEEP,
    WAIT_EVENT_RECOVERY_APPLY_DELAY,
    WAIT_EVENT_RECOVERY_RETRIEVE_RETRY_INTERVAL,
    WAIT_EVENT_VACUUM_DELAY
} WaitEventTimeout;

/* ----------
 * Wait Events - IO
 *
 * Use this category when a process is waiting for a IO.
 * ----------
 */
typedef enum
{
    WAIT_EVENT_BASEBACKUP_READ = PG_WAIT_IO,
    WAIT_EVENT_BUFFILE_READ,
    WAIT_EVENT_BUFFILE_WRITE,
    WAIT_EVENT_BUFFILE_TRUNCATE,
    WAIT_EVENT_CONTROL_FILE_READ,
    WAIT_EVENT_CONTROL_FILE_SYNC,
    WAIT_EVENT_CONTROL_FILE_SYNC_UPDATE,
    WAIT_EVENT_CONTROL_FILE_WRITE,
    WAIT_EVENT_CONTROL_FILE_WRITE_UPDATE,
    WAIT_EVENT_COPY_FILE_READ,
    WAIT_EVENT_COPY_FILE_WRITE,
    WAIT_EVENT_DATA_FILE_EXTEND,
    WAIT_EVENT_DATA_FILE_FLUSH,
    WAIT_EVENT_DATA_FILE_IMMEDIATE_SYNC,
    WAIT_EVENT_DATA_FILE_PREFETCH,
    WAIT_EVENT_DATA_FILE_READ,
    WAIT_EVENT_DATA_FILE_SYNC,
    WAIT_EVENT_DATA_FILE_TRUNCATE,
    WAIT_EVENT_DATA_FILE_WRITE,
    WAIT_EVENT_DSM_FILL_ZERO_WRITE,
    WAIT_EVENT_LOCK_FILE_ADDTODATADIR_READ,
    WAIT_EVENT_LOCK_FILE_ADDTODATADIR_SYNC,
    WAIT_EVENT_LOCK_FILE_ADDTODATADIR_WRITE,
    WAIT_EVENT_LOCK_FILE_CREATE_READ,
    WAIT_EVENT_LOCK_FILE_CREATE_SYNC,
    WAIT_EVENT_LOCK_FILE_CREATE_WRITE,
    WAIT_EVENT_LOCK_FILE_RECHECKDATADIR_READ,
    WAIT_EVENT_LOGICAL_REWRITE_CHECKPOINT_SYNC,
    WAIT_EVENT_LOGICAL_REWRITE_MAPPING_SYNC,
    WAIT_EVENT_LOGICAL_REWRITE_MAPPING_WRITE,
    WAIT_EVENT_LOGICAL_REWRITE_SYNC,
    WAIT_EVENT_LOGICAL_REWRITE_TRUNCATE,
    WAIT_EVENT_LOGICAL_REWRITE_WRITE,
    WAIT_EVENT_RELATION_MAP_READ,
    WAIT_EVENT_RELATION_MAP_SYNC,
    WAIT_EVENT_RELATION_MAP_WRITE,
    WAIT_EVENT_REORDER_BUFFER_READ,
    WAIT_EVENT_REORDER_BUFFER_WRITE,
    WAIT_EVENT_REORDER_LOGICAL_MAPPING_READ,
    WAIT_EVENT_REPLICATION_SLOT_READ,
    WAIT_EVENT_REPLICATION_SLOT_RESTORE_SYNC,
    WAIT_EVENT_REPLICATION_SLOT_SYNC,
    WAIT_EVENT_REPLICATION_SLOT_WRITE,
    WAIT_EVENT_SLRU_FLUSH_SYNC,
    WAIT_EVENT_SLRU_READ,
    WAIT_EVENT_SLRU_SYNC,
    WAIT_EVENT_SLRU_WRITE,
    WAIT_EVENT_SNAPBUILD_READ,
    WAIT_EVENT_SNAPBUILD_SYNC,
    WAIT_EVENT_SNAPBUILD_WRITE,
    WAIT_EVENT_TIMELINE_HISTORY_FILE_SYNC,
    WAIT_EVENT_TIMELINE_HISTORY_FILE_WRITE,
    WAIT_EVENT_TIMELINE_HISTORY_READ,
    WAIT_EVENT_TIMELINE_HISTORY_SYNC,
    WAIT_EVENT_TIMELINE_HISTORY_WRITE,
    WAIT_EVENT_TWOPHASE_FILE_READ,
    WAIT_EVENT_TWOPHASE_FILE_SYNC,
    WAIT_EVENT_TWOPHASE_FILE_WRITE,
    WAIT_EVENT_WALSENDER_TIMELINE_HISTORY_READ,
    WAIT_EVENT_WAL_BOOTSTRAP_SYNC,
    WAIT_EVENT_WAL_BOOTSTRAP_WRITE,
    WAIT_EVENT_WAL_COPY_READ,
    WAIT_EVENT_WAL_COPY_SYNC,
    WAIT_EVENT_WAL_COPY_WRITE,
    WAIT_EVENT_WAL_INIT_SYNC,
    WAIT_EVENT_WAL_INIT_WRITE,
    WAIT_EVENT_WAL_READ,
    WAIT_EVENT_WAL_SYNC,
    WAIT_EVENT_WAL_SYNC_METHOD_ASSIGN,
    WAIT_EVENT_WAL_WRITE,
    WAIT_EVENT_LOGICAL_CHANGES_READ,
    WAIT_EVENT_LOGICAL_CHANGES_WRITE,
    WAIT_EVENT_LOGICAL_SUBXACT_READ,
    WAIT_EVENT_LOGICAL_SUBXACT_WRITE
} WaitEventIO;

/* ----------
 * Command type for progress reporting purposes
 * ----------
 */
typedef enum ProgressCommandType
{
    PROGRESS_COMMAND_INVALID,
    PROGRESS_COMMAND_VACUUM,
    PROGRESS_COMMAND_ANALYZE,
    PROGRESS_COMMAND_CLUSTER,
    PROGRESS_COMMAND_CREATE_INDEX,
    PROGRESS_COMMAND_BASEBACKUP,
    PROGRESS_COMMAND_COPY
} ProgressCommandType;

#define PGSTAT_NUM_PROGRESS_PARAM   20

/* ----------
 * Shared-memory data structures
 * ----------
 */


/*
 * PgBackendSSLStatus
 *
 * For each backend, we keep the SSL status in a separate struct, that
 * is only filled in if SSL is enabled.
 *
 * All char arrays must be null-terminated.
 */
typedef struct PgBackendSSLStatus
{
    /* Information about SSL connection */
    int         ssl_bits;
    bool        ssl_compression;
    char        ssl_version[NAMEDATALEN];
    char        ssl_cipher[NAMEDATALEN];
    char        ssl_client_dn[NAMEDATALEN];

    /*
     * serial number is max "20 octets" per RFC 5280, so this size should be
     * fine
     */
    char        ssl_client_serial[NAMEDATALEN];

    char        ssl_issuer_dn[NAMEDATALEN];
} PgBackendSSLStatus;

/*
 * PgBackendGSSStatus
 *
 * For each backend, we keep the GSS status in a separate struct, that
 * is only filled in if GSS is enabled.
 *
 * All char arrays must be null-terminated.
 */
typedef struct PgBackendGSSStatus
{
    /* Information about GSSAPI connection */
    char        gss_princ[NAMEDATALEN]; /* GSSAPI Principal used to auth */
    bool        gss_auth;       /* If GSSAPI authentication was used */
    bool        gss_enc;        /* If encryption is being used */

} PgBackendGSSStatus;


/* ----------
 * PgBackendStatus
 *
 * Each live backend maintains a PgBackendStatus struct in shared memory
 * showing its current activity.  (The structs are allocated according to
 * BackendId, but that is not critical.)  Note that the collector process
 * has no involvement in, or even access to, these structs.
 *
 * Each auxiliary process also maintains a PgBackendStatus struct in shared
 * memory.
 * ----------
 */
typedef struct PgBackendStatus
{
    /*
     * To avoid locking overhead, we use the following protocol: a backend
     * increments st_changecount before modifying its entry, and again after
     * finishing a modification.  A would-be reader should note the value of
     * st_changecount, copy the entry into private memory, then check
     * st_changecount again.  If the value hasn't changed, and if it's even,
     * the copy is valid; otherwise start over.  This makes updates cheap
     * while reads are potentially expensive, but that's the tradeoff we want.
     *
     * The above protocol needs memory barriers to ensure that the apparent
     * order of execution is as it desires.  Otherwise, for example, the CPU
     * might rearrange the code so that st_changecount is incremented twice
     * before the modification on a machine with weak memory ordering.  Hence,
     * use the macros defined below for manipulating st_changecount, rather
     * than touching it directly.
     */
    int         st_changecount;

    /* The entry is valid iff st_procpid > 0, unused if st_procpid == 0 */
    int         st_procpid;

    /* Type of backends */
    BackendType st_backendType;

    /* Times when current backend, transaction, and activity started */
    TimestampTz st_proc_start_timestamp;
    TimestampTz st_xact_start_timestamp;
    TimestampTz st_activity_start_timestamp;
    TimestampTz st_state_start_timestamp;

    /* Database OID, owning user's OID, connection client address */
    Oid         st_databaseid;
    Oid         st_userid;
    SockAddr    st_clientaddr;
    char       *st_clienthostname;  /* MUST be null-terminated */

    /* Information about SSL connection */
    bool        st_ssl;
    PgBackendSSLStatus *st_sslstatus;

    /* Information about GSSAPI connection */
    bool        st_gss;
    PgBackendGSSStatus *st_gssstatus;

    /* current state */
    BackendState st_state;

    /* application name; MUST be null-terminated */
    char       *st_appname;

    /*
     * Current command string; MUST be null-terminated. Note that this string
     * possibly is truncated in the middle of a multi-byte character. As
     * activity strings are stored more frequently than read, that allows to
     * move the cost of correct truncation to the display side. Use
     * pgstat_clip_activity() to truncate correctly.
     */
    char       *st_activity_raw;

    /*
     * Command progress reporting.  Any command which wishes can advertise
     * that it is running by setting st_progress_command,
     * st_progress_command_target, and st_progress_param[].
     * st_progress_command_target should be the OID of the relation which the
     * command targets (we assume there's just one, as this is meant for
     * utility commands), but the meaning of each element in the
     * st_progress_param array is command-specific.
     */
    ProgressCommandType st_progress_command;
    Oid         st_progress_command_target;
    int64       st_progress_param[PGSTAT_NUM_PROGRESS_PARAM];
} PgBackendStatus;

/*
 * Macros to load and store st_changecount with appropriate memory barriers.
 *
 * Use PGSTAT_BEGIN_WRITE_ACTIVITY() before, and PGSTAT_END_WRITE_ACTIVITY()
 * after, modifying the current process's PgBackendStatus data.  Note that,
 * since there is no mechanism for cleaning up st_changecount after an error,
 * THESE MACROS FORM A CRITICAL SECTION.  Any error between them will be
 * promoted to PANIC, causing a database restart to clean up shared memory!
 * Hence, keep the critical section as short and straight-line as possible.
 * Aside from being safer, that minimizes the window in which readers will
 * have to loop.
 *
 * Reader logic should follow this sketch:
 *
 *      for (;;)
 *      {
 *          int before_ct, after_ct;
 *
 *          pgstat_begin_read_activity(beentry, before_ct);
 *          ... copy beentry data to local memory ...
 *          pgstat_end_read_activity(beentry, after_ct);
 *          if (pgstat_read_activity_complete(before_ct, after_ct))
 *              break;
 *          CHECK_FOR_INTERRUPTS();
 *      }
 *
 * For extra safety, we generally use volatile beentry pointers, although
 * the memory barriers should theoretically be sufficient.
 */
#define PGSTAT_BEGIN_WRITE_ACTIVITY(beentry) \
    do { \
        START_CRIT_SECTION(); \
        (beentry)->st_changecount++; \
        pg_write_barrier(); \
    } while (0)

#define PGSTAT_END_WRITE_ACTIVITY(beentry) \
    do { \
        pg_write_barrier(); \
        (beentry)->st_changecount++; \
        Assert(((beentry)->st_changecount & 1) == 0); \
        END_CRIT_SECTION(); \
    } while (0)

#define pgstat_begin_read_activity(beentry, before_changecount) \
    do { \
        (before_changecount) = (beentry)->st_changecount; \
        pg_read_barrier(); \
    } while (0)

#define pgstat_end_read_activity(beentry, after_changecount) \
    do { \
        pg_read_barrier(); \
        (after_changecount) = (beentry)->st_changecount; \
    } while (0)

#define pgstat_read_activity_complete(before_changecount, after_changecount) \
    ((before_changecount) == (after_changecount) && \
     ((before_changecount) & 1) == 0)


/* ----------
 * LocalPgBackendStatus
 *
 * When we build the backend status array, we use LocalPgBackendStatus to be
 * able to add new values to the struct when needed without adding new fields
 * to the shared memory. It contains the backend status as a first member.
 * ----------
 */
typedef struct LocalPgBackendStatus
{
    /*
     * Local version of the backend status entry.
     */
    PgBackendStatus backendStatus;

    /*
     * The xid of the current transaction if available, InvalidTransactionId
     * if not.
     */
    TransactionId backend_xid;

    /*
     * The xmin of the current session if available, InvalidTransactionId if
     * not.
     */
    TransactionId backend_xmin;
} LocalPgBackendStatus;

/*
 * Working state needed to accumulate per-function-call timing statistics.
 */
typedef struct PgStat_FunctionCallUsage
{
    /* Link to function's hashtable entry (must still be there at exit!) */
    /* NULL means we are not tracking the current function call */
    PgStat_FunctionCounts *fs;
    /* Total time previously charged to function, as of function start */
    instr_time  save_f_total_time;
    /* Backend-wide total time as of function start */
    instr_time  save_total;
    /* system clock as of function start */
    instr_time  f_start;
} PgStat_FunctionCallUsage;


/* ----------
 * GUC parameters
 * ----------
 */
extern PGDLLIMPORT bool pgstat_track_activities;
extern PGDLLIMPORT bool pgstat_track_counts;
extern PGDLLIMPORT int pgstat_track_functions;
extern PGDLLIMPORT int pgstat_track_activity_query_size;
extern char *pgstat_stat_directory;
extern char *pgstat_stat_tmpname;
extern char *pgstat_stat_filename;

/*
 * BgWriter statistics counters are updated directly by bgwriter and bufmgr
 */
extern PgStat_MsgBgWriter BgWriterStats;

/*
 * WAL statistics counter is updated by backends and background processes
 */
extern PgStat_MsgWal WalStats;

/*
 * Updated by pgstat_count_buffer_*_time macros
 */
extern PgStat_Counter pgStatBlockReadTime;
extern PgStat_Counter pgStatBlockWriteTime;

/*
 * Updated by the traffic cop and in errfinish()
 */
extern SessionEndType pgStatSessionEndCause;

/* ----------
 * Functions called from postmaster
 * ----------
 */
extern Size BackendStatusShmemSize(void);
extern void CreateSharedBackendStatus(void);

extern void pgstat_init(void);
extern int  pgstat_start(void);
extern void pgstat_reset_all(void);
extern void allow_immediate_pgstat_restart(void);

#ifdef EXEC_BACKEND
extern void PgstatCollectorMain(int argc, char *argv[]) pg_attribute_noreturn();
#endif


/* ----------
 * Functions called from backends
 * ----------
 */
extern void pgstat_ping(void);

extern void pgstat_report_stat(bool force);
extern void pgstat_vacuum_stat(void);
extern void pgstat_drop_database(Oid databaseid);

extern void pgstat_clear_snapshot(void);
extern void pgstat_reset_counters(void);
extern void pgstat_reset_shared_counters(const char *);
extern void pgstat_reset_single_counter(Oid objectid, PgStat_Single_Reset_Type type);
extern void pgstat_reset_slru_counter(const char *);
extern void pgstat_reset_replslot_counter(const char *name);

extern void pgstat_report_autovac(Oid dboid);
extern void pgstat_report_vacuum(Oid tableoid, bool shared,
                                 PgStat_Counter livetuples, PgStat_Counter deadtuples);
extern void pgstat_report_analyze(Relation rel,
                                  PgStat_Counter livetuples, PgStat_Counter deadtuples,
                                  bool resetcounter);

extern void pgstat_report_recovery_conflict(int reason);
extern void pgstat_report_deadlock(void);
extern void pgstat_report_checksum_failures_in_db(Oid dboid, int failurecount);
extern void pgstat_report_checksum_failure(void);
extern void pgstat_report_replslot(const char *slotname, int spilltxns, int spillcount,
                                   int spillbytes, int streamtxns, int streamcount, int streambytes);
extern void pgstat_report_replslot_drop(const char *slotname);

extern void pgstat_initialize(void);
extern void pgstat_bestart(void);

extern void pgstat_report_activity(BackendState state, const char *cmd_str);
extern void pgstat_report_tempfile(size_t filesize);
extern void pgstat_report_appname(const char *appname);
extern void pgstat_report_xact_timestamp(TimestampTz tstamp);
extern const char *pgstat_get_wait_event(uint32 wait_event_info);
extern const char *pgstat_get_wait_event_type(uint32 wait_event_info);
extern const char *pgstat_get_backend_current_activity(int pid, bool checkUser);
extern const char *pgstat_get_crashed_backend_activity(int pid, char *buffer,
                                                       int buflen);

extern void pgstat_progress_start_command(ProgressCommandType cmdtype,
                                          Oid relid);
extern void pgstat_progress_update_param(int index, int64 val);
extern void pgstat_progress_update_multi_param(int nparam, const int *index,
                                               const int64 *val);
extern void pgstat_progress_end_command(void);

extern PgStat_TableStatus *find_tabstat_entry(Oid rel_id);
extern PgStat_BackendFunctionEntry *find_funcstat_entry(Oid func_id);

extern void pgstat_initstats(Relation rel);

extern char *pgstat_clip_activity(const char *raw_activity);

/* ----------
 * pgstat_report_wait_start() -
 *
 *  Called from places where server process needs to wait.  This is called
 *  to report wait event information.  The wait information is stored
 *  as 4-bytes where first byte represents the wait event class (type of
 *  wait, for different types of wait, refer WaitClass) and the next
 *  3-bytes represent the actual wait event.  Currently 2-bytes are used
 *  for wait event which is sufficient for current usage, 1-byte is
 *  reserved for future usage.
 *
 * NB: this *must* be able to survive being called before MyProc has been
 * initialized.
 * ----------
 */
static inline void
pgstat_report_wait_start(uint32 wait_event_info)
{
    volatile PGPROC *proc = MyProc;

    if (!pgstat_track_activities || !proc)
        return;

    /*
     * Since this is a four-byte field which is always read and written as
     * four-bytes, updates are atomic.
     */
    proc->wait_event_info = wait_event_info;
}

/* ----------
 * pgstat_report_wait_end() -
 *
 *  Called to report end of a wait.
 *
 * NB: this *must* be able to survive being called before MyProc has been
 * initialized.
 * ----------
 */
static inline void
pgstat_report_wait_end(void)
{
    volatile PGPROC *proc = MyProc;

    if (!pgstat_track_activities || !proc)
        return;

    /*
     * Since this is a four-byte field which is always read and written as
     * four-bytes, updates are atomic.
     */
    proc->wait_event_info = 0;
}

/* nontransactional event counts are simple enough to inline */

#define pgstat_count_heap_scan(rel)                                 \
    do {                                                            \
        if ((rel)->pgstat_info != NULL)                             \
            (rel)->pgstat_info->t_counts.t_numscans++;              \
    } while (0)
#define pgstat_count_heap_getnext(rel)                              \
    do {                                                            \
        if ((rel)->pgstat_info != NULL)                             \
            (rel)->pgstat_info->t_counts.t_tuples_returned++;       \
    } while (0)
#define pgstat_count_heap_fetch(rel)                                \
    do {                                                            \
        if ((rel)->pgstat_info != NULL)                             \
            (rel)->pgstat_info->t_counts.t_tuples_fetched++;        \
    } while (0)
#define pgstat_count_index_scan(rel)                                \
    do {                                                            \
        if ((rel)->pgstat_info != NULL)                             \
            (rel)->pgstat_info->t_counts.t_numscans++;              \
    } while (0)
#define pgstat_count_index_tuples(rel, n)                           \
    do {                                                            \
        if ((rel)->pgstat_info != NULL)                             \
            (rel)->pgstat_info->t_counts.t_tuples_returned += (n);  \
    } while (0)
#define pgstat_count_buffer_read(rel)                               \
    do {                                                            \
        if ((rel)->pgstat_info != NULL)                             \
            (rel)->pgstat_info->t_counts.t_blocks_fetched++;        \
    } while (0)
#define pgstat_count_buffer_hit(rel)                                \
    do {                                                            \
        if ((rel)->pgstat_info != NULL)                             \
            (rel)->pgstat_info->t_counts.t_blocks_hit++;            \
    } while (0)
#define pgstat_count_buffer_read_time(n)                            \
    (pgStatBlockReadTime += (n))
#define pgstat_count_buffer_write_time(n)                           \
    (pgStatBlockWriteTime += (n))

extern void pgstat_count_heap_insert(Relation rel, PgStat_Counter n);
extern void pgstat_count_heap_update(Relation rel, bool hot);
extern void pgstat_count_heap_delete(Relation rel);
extern void pgstat_count_truncate(Relation rel);
extern void pgstat_update_heap_dead_tuples(Relation rel, int delta);

struct FunctionCallInfoBaseData;
extern void pgstat_init_function_usage(struct FunctionCallInfoBaseData *fcinfo,
                                       PgStat_FunctionCallUsage *fcu);
extern void pgstat_end_function_usage(PgStat_FunctionCallUsage *fcu,
                                      bool finalize);

extern void AtEOXact_PgStat(bool isCommit, bool parallel);
extern void AtEOSubXact_PgStat(bool isCommit, int nestDepth);

extern void AtPrepare_PgStat(void);
extern void PostPrepare_PgStat(void);

extern void pgstat_twophase_postcommit(TransactionId xid, uint16 info,
                                       void *recdata, uint32 len);
extern void pgstat_twophase_postabort(TransactionId xid, uint16 info,
                                      void *recdata, uint32 len);

extern void pgstat_send_archiver(const char *xlog, bool failed);
extern void pgstat_send_bgwriter(void);
extern void pgstat_send_wal(void);

/* ----------
 * Support functions for the SQL-callable functions to
 * generate the pgstat* views.
 * ----------
 */
extern PgStat_StatDBEntry *pgstat_fetch_stat_dbentry(Oid dbid);
extern PgStat_StatTabEntry *pgstat_fetch_stat_tabentry(Oid relid);
extern PgBackendStatus *pgstat_fetch_stat_beentry(int beid);
extern LocalPgBackendStatus *pgstat_fetch_stat_local_beentry(int beid);
extern PgStat_StatFuncEntry *pgstat_fetch_stat_funcentry(Oid funcid);
extern int  pgstat_fetch_stat_numbackends(void);
extern PgStat_ArchiverStats *pgstat_fetch_stat_archiver(void);
extern PgStat_GlobalStats *pgstat_fetch_global(void);
extern PgStat_WalStats *pgstat_fetch_stat_wal(void);
extern PgStat_SLRUStats *pgstat_fetch_slru(void);
extern PgStat_ReplSlotStats *pgstat_fetch_replslot(int *nslots_p);

extern void pgstat_count_slru_page_zeroed(int slru_idx);
extern void pgstat_count_slru_page_hit(int slru_idx);
extern void pgstat_count_slru_page_read(int slru_idx);
extern void pgstat_count_slru_page_written(int slru_idx);
extern void pgstat_count_slru_page_exists(int slru_idx);
extern void pgstat_count_slru_flush(int slru_idx);
extern void pgstat_count_slru_truncate(int slru_idx);
extern const char *pgstat_slru_name(int slru_idx);
extern int  pgstat_slru_index(const char *name);

#endif                          /* PGSTAT_H */