injection_stats.c

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/*--------------------------------------------------------------------------
 *
 * injection_stats.c
 *      Code for statistics of injection points.
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *      src/test/modules/injection_points/injection_stats.c
 *
 * -------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "fmgr.h"
 
#include "common/hashfn.h"
#include "injection_stats.h"
#include "pgstat.h"
#include "utils/builtins.h"
#include "utils/pgstat_internal.h"
 
/* Structures for statistics of injection points */
typedef struct PgStat_StatInjEntry
{
    PgStat_Counter numcalls;    /* number of times point has been run */
} PgStat_StatInjEntry;
 
typedef struct PgStatShared_InjectionPoint
{
    PgStatShared_Common header;
    PgStat_StatInjEntry stats;
} PgStatShared_InjectionPoint;
 
static bool injection_stats_flush_cb(PgStat_EntryRef *entry_ref, bool nowait);
 
static const PgStat_KindInfo injection_stats = {
    .name = "injection_points",
    .fixed_amount = false,      /* Bounded by the number of points */
 
    /* Injection points are system-wide */
    .accessed_across_databases = true,
 
    .shared_size = sizeof(PgStatShared_InjectionPoint),
    .shared_data_off = offsetof(PgStatShared_InjectionPoint, stats),
    .shared_data_len = sizeof(((PgStatShared_InjectionPoint *) 0)->stats),
    .pending_size = sizeof(PgStat_StatInjEntry),
    .flush_pending_cb = injection_stats_flush_cb,
};
 
/*
 * Compute stats entry idx from point name with an 8-byte hash.
 */
#define PGSTAT_INJ_IDX(name) hash_bytes_extended((const unsigned char *) name, strlen(name), 0)
 
/*
 * Kind ID reserved for statistics of injection points.
 */
#define PGSTAT_KIND_INJECTION   129
 
/* Track if stats are loaded */
static bool inj_stats_loaded = false;
 
/*
 * Callback for stats handling
 */
static bool
injection_stats_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
{
    PgStat_StatInjEntry *localent;
    PgStatShared_InjectionPoint *shfuncent;
 
    localent = (PgStat_StatInjEntry *) entry_ref->pending;
    shfuncent = (PgStatShared_InjectionPoint *) entry_ref->shared_stats;
 
    if (!pgstat_lock_entry(entry_ref, nowait))
        return false;
 
    shfuncent->stats.numcalls += localent->numcalls;
    return true;
}
 
/*
 * Support function for the SQL-callable pgstat* functions.  Returns
 * a pointer to the injection point statistics struct.
 */
static PgStat_StatInjEntry *
pgstat_fetch_stat_injentry(const char *name)
{
    PgStat_StatInjEntry *entry = NULL;
 
    if (!inj_stats_loaded || !inj_stats_enabled)
        return NULL;
 
    /* Compile the lookup key as a hash of the point name */
    entry = (PgStat_StatInjEntry *) pgstat_fetch_entry(PGSTAT_KIND_INJECTION,
                                                       InvalidOid,
                                                       PGSTAT_INJ_IDX(name));
    return entry;
}
 
/*
 * Workhorse to do the registration work, called in _PG_init().
 */
void
pgstat_register_inj(void)
{
    pgstat_register_kind(PGSTAT_KIND_INJECTION, &injection_stats);
 
    /* mark stats as loaded */
    inj_stats_loaded = true;
}
 
/*
 * Report injection point creation.
 */
void
pgstat_create_inj(const char *name)
{
    PgStat_EntryRef *entry_ref;
    PgStatShared_InjectionPoint *shstatent;
 
    /* leave if disabled */
    if (!inj_stats_loaded || !inj_stats_enabled)
        return;
 
    entry_ref = pgstat_get_entry_ref_locked(PGSTAT_KIND_INJECTION, InvalidOid,
                                            PGSTAT_INJ_IDX(name), false);
    shstatent = (PgStatShared_InjectionPoint *) entry_ref->shared_stats;
 
    /* initialize shared memory data */
    memset(&shstatent->stats, 0, sizeof(shstatent->stats));
    pgstat_unlock_entry(entry_ref);
}
 
/*
 * Report injection point drop.
 */
void
pgstat_drop_inj(const char *name)
{
    /* leave if disabled */
    if (!inj_stats_loaded || !inj_stats_enabled)
        return;
 
    if (!pgstat_drop_entry(PGSTAT_KIND_INJECTION, InvalidOid,
                           PGSTAT_INJ_IDX(name)))
        pgstat_request_entry_refs_gc();
}
 
/*
 * Report statistics for injection point.
 *
 * This is simple because the set of stats to report currently is simple:
 * track the number of times a point has been run.
 */
void
pgstat_report_inj(const char *name)
{
    PgStat_EntryRef *entry_ref;
    PgStatShared_InjectionPoint *shstatent;
    PgStat_StatInjEntry *statent;
 
    /* leave if disabled */
    if (!inj_stats_loaded || !inj_stats_enabled)
        return;
 
    entry_ref = pgstat_get_entry_ref_locked(PGSTAT_KIND_INJECTION, InvalidOid,
                                            PGSTAT_INJ_IDX(name), false);
 
    shstatent = (PgStatShared_InjectionPoint *) entry_ref->shared_stats;
    statent = &shstatent->stats;
 
    /* Update the injection point statistics */
    statent->numcalls++;
 
    pgstat_unlock_entry(entry_ref);
}
 
/*
 * SQL function returning the number of times an injection point
 * has been called.
 */
PG_FUNCTION_INFO_V1(injection_points_stats_numcalls);
Datum
injection_points_stats_numcalls(PG_FUNCTION_ARGS)
{
    char       *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
    PgStat_StatInjEntry *entry = pgstat_fetch_stat_injentry(name);
 
    if (entry == NULL)
        PG_RETURN_NULL();
 
    PG_RETURN_INT64(entry->numcalls);
}