pgstat_function.c

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/* -------------------------------------------------------------------------
 *
 * pgstat_function.c
 *    Implementation of function statistics.
 *
 * This file contains the implementation of function 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_function.c
 * -------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "fmgr.h"
#include "utils/inval.h"
#include "utils/pgstat_internal.h"
#include "utils/syscache.h"
 
 
/* ----------
 * GUC parameters
 * ----------
 */
int         pgstat_track_functions = TRACK_FUNC_OFF;
 
 
/*
 * Total time charged to functions so far in the current backend.
 * We use this to help separate "self" and "other" time charges.
 * (We assume this initializes to zero.)
 */
static instr_time total_func_time;
 
 
/*
 * Ensure that stats are dropped if transaction aborts.
 */
void
pgstat_create_function(Oid proid)
{
    pgstat_create_transactional(PGSTAT_KIND_FUNCTION,
                                MyDatabaseId,
                                proid);
}
 
/*
 * Ensure that stats are dropped if transaction commits.
 *
 * NB: This is only reliable because pgstat_init_function_usage() does some
 * extra work. If other places start emitting function stats they likely need
 * similar logic.
 */
void
pgstat_drop_function(Oid proid)
{
    pgstat_drop_transactional(PGSTAT_KIND_FUNCTION,
                              MyDatabaseId,
                              proid);
}
 
/*
 * Initialize function call usage data.
 * Called by the executor before invoking a function.
 */
void
pgstat_init_function_usage(FunctionCallInfo fcinfo,
                           PgStat_FunctionCallUsage *fcu)
{
    PgStat_EntryRef *entry_ref;
    PgStat_FunctionCounts *pending;
    bool        created_entry;
 
    if (pgstat_track_functions <= fcinfo->flinfo->fn_stats)
    {
        /* stats not wanted */
        fcu->fs = NULL;
        return;
    }
 
    entry_ref = pgstat_prep_pending_entry(PGSTAT_KIND_FUNCTION,
                                          MyDatabaseId,
                                          fcinfo->flinfo->fn_oid,
                                          &created_entry);
 
    /*
     * If no shared entry already exists, check if the function has been
     * deleted concurrently. This can go unnoticed until here because
     * executing a statement that just calls a function, does not trigger
     * cache invalidation processing. The reason we care about this case is
     * that otherwise we could create a new stats entry for an already dropped
     * function (for relations etc this is not possible because emitting stats
     * requires a lock for the relation to already have been acquired).
     *
     * It's somewhat ugly to have a behavioral difference based on
     * track_functions being enabled/disabled. But it seems acceptable, given
     * that there's already behavioral differences depending on whether the
     * function is the caches etc.
     *
     * For correctness it'd be sufficient to set ->dropped to true. However,
     * the accepted invalidation will commonly cause "low level" failures in
     * PL code, with an OID in the error message. Making this harder to
     * test...
     */
    if (created_entry)
    {
        AcceptInvalidationMessages();
        if (!SearchSysCacheExists1(PROCOID, ObjectIdGetDatum(fcinfo->flinfo->fn_oid)))
        {
            pgstat_drop_entry(PGSTAT_KIND_FUNCTION, MyDatabaseId,
                              fcinfo->flinfo->fn_oid);
            ereport(ERROR, errcode(ERRCODE_UNDEFINED_FUNCTION),
                    errmsg("function call to dropped function"));
        }
    }
 
    pending = entry_ref->pending;
 
    fcu->fs = pending;
 
    /* save stats for this function, later used to compensate for recursion */
    fcu->save_f_total_time = pending->total_time;
 
    /* save current backend-wide total time */
    fcu->save_total = total_func_time;
 
    /* get clock time as of function start */
    INSTR_TIME_SET_CURRENT(fcu->start);
}
 
/*
 * Calculate function call usage and update stat counters.
 * Called by the executor after invoking a function.
 *
 * In the case of a set-returning function that runs in value-per-call mode,
 * we will see multiple pgstat_init_function_usage/pgstat_end_function_usage
 * calls for what the user considers a single call of the function.  The
 * finalize flag should be TRUE on the last call.
 */
void
pgstat_end_function_usage(PgStat_FunctionCallUsage *fcu, bool finalize)
{
    PgStat_FunctionCounts *fs = fcu->fs;
    instr_time  total;
    instr_time  others;
    instr_time  self;
 
    /* stats not wanted? */
    if (fs == NULL)
        return;
 
    /* total elapsed time in this function call */
    INSTR_TIME_SET_CURRENT(total);
    INSTR_TIME_SUBTRACT(total, fcu->start);
 
    /* self usage: elapsed minus anything already charged to other calls */
    others = total_func_time;
    INSTR_TIME_SUBTRACT(others, fcu->save_total);
    self = total;
    INSTR_TIME_SUBTRACT(self, others);
 
    /* update backend-wide total time */
    INSTR_TIME_ADD(total_func_time, self);
 
    /*
     * Compute the new total_time as the total elapsed time added to the
     * pre-call value of total_time.  This is necessary to avoid
     * double-counting any time taken by recursive calls of myself.  (We do
     * not need any similar kluge for self time, since that already excludes
     * any recursive calls.)
     */
    INSTR_TIME_ADD(total, fcu->save_f_total_time);
 
    /* update counters in function stats table */
    if (finalize)
        fs->numcalls++;
    fs->total_time = total;
    INSTR_TIME_ADD(fs->self_time, self);
}
 
/*
 * Flush out pending stats for the entry
 *
 * If nowait is true, this function returns false if lock could not
 * immediately acquired, otherwise true is returned.
 */
bool
pgstat_function_flush_cb(PgStat_EntryRef *entry_ref, bool nowait)
{
    PgStat_FunctionCounts *localent;
    PgStatShared_Function *shfuncent;
 
    localent = (PgStat_FunctionCounts *) entry_ref->pending;
    shfuncent = (PgStatShared_Function *) entry_ref->shared_stats;
 
    /* localent always has non-zero content */
 
    if (!pgstat_lock_entry(entry_ref, nowait))
        return false;
 
    shfuncent->stats.numcalls += localent->numcalls;
    shfuncent->stats.total_time +=
        INSTR_TIME_GET_MICROSEC(localent->total_time);
    shfuncent->stats.self_time +=
        INSTR_TIME_GET_MICROSEC(localent->self_time);
 
    pgstat_unlock_entry(entry_ref);
 
    return true;
}
 
/*
 * find any existing PgStat_FunctionCounts entry for specified function
 *
 * If no entry, return NULL, don't create a new one
 */
PgStat_FunctionCounts *
find_funcstat_entry(Oid func_id)
{
    PgStat_EntryRef *entry_ref;
 
    entry_ref = pgstat_fetch_pending_entry(PGSTAT_KIND_FUNCTION, MyDatabaseId, func_id);
 
    if (entry_ref)
        return entry_ref->pending;
    return NULL;
}
 
/*
 * Support function for the SQL-callable pgstat* functions. Returns
 * the collected statistics for one function or NULL.
 */
PgStat_StatFuncEntry *
pgstat_fetch_stat_funcentry(Oid func_id)
{
    return (PgStat_StatFuncEntry *)
        pgstat_fetch_entry(PGSTAT_KIND_FUNCTION, MyDatabaseId, func_id);
}