instrument.c

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/*-------------------------------------------------------------------------
 *
 * instrument.c
 *   functions for instrumentation of plan execution
 *
 *
 * Copyright (c) 2001-2013, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/executor/instrument.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <unistd.h>

#include "executor/instrument.h"

BufferUsage pgBufferUsage;

static void BufferUsageAccumDiff(BufferUsage *dst,
                     const BufferUsage *add, const BufferUsage *sub);


/* Allocate new instrumentation structure(s) */
Instrumentation *
InstrAlloc(int n, int instrument_options)
{
    Instrumentation *instr;

    /* initialize all fields to zeroes, then modify as needed */
    instr = palloc0(n * sizeof(Instrumentation));
    if (instrument_options & (INSTRUMENT_BUFFERS | INSTRUMENT_TIMER))
    {
        bool        need_buffers = (instrument_options & INSTRUMENT_BUFFERS) != 0;
        bool        need_timer = (instrument_options & INSTRUMENT_TIMER) != 0;
        int         i;

        for (i = 0; i < n; i++)
        {
            instr[i].need_bufusage = need_buffers;
            instr[i].need_timer = need_timer;
        }
    }

    return instr;
}

/* Entry to a plan node */
void
InstrStartNode(Instrumentation *instr)
{
    if (instr->need_timer)
    {
        if (INSTR_TIME_IS_ZERO(instr->starttime))
            INSTR_TIME_SET_CURRENT(instr->starttime);
        else
            elog(ERROR, "InstrStartNode called twice in a row");
    }

    /* save buffer usage totals at node entry, if needed */
    if (instr->need_bufusage)
        instr->bufusage_start = pgBufferUsage;
}

/* Exit from a plan node */
void
InstrStopNode(Instrumentation *instr, double nTuples)
{
    instr_time  endtime;

    /* count the returned tuples */
    instr->tuplecount += nTuples;

    /* let's update the time only if the timer was requested */
    if (instr->need_timer)
    {
        if (INSTR_TIME_IS_ZERO(instr->starttime))
            elog(ERROR, "InstrStopNode called without start");

        INSTR_TIME_SET_CURRENT(endtime);
        INSTR_TIME_ACCUM_DIFF(instr->counter, endtime, instr->starttime);

        INSTR_TIME_SET_ZERO(instr->starttime);
    }

    /* Add delta of buffer usage since entry to node's totals */
    if (instr->need_bufusage)
        BufferUsageAccumDiff(&instr->bufusage,
                             &pgBufferUsage, &instr->bufusage_start);

    /* Is this the first tuple of this cycle? */
    if (!instr->running)
    {
        instr->running = true;
        instr->firsttuple = INSTR_TIME_GET_DOUBLE(instr->counter);
    }
}

/* Finish a run cycle for a plan node */
void
InstrEndLoop(Instrumentation *instr)
{
    double      totaltime;

    /* Skip if nothing has happened, or already shut down */
    if (!instr->running)
        return;

    if (!INSTR_TIME_IS_ZERO(instr->starttime))
        elog(ERROR, "InstrEndLoop called on running node");

    /* Accumulate per-cycle statistics into totals */
    totaltime = INSTR_TIME_GET_DOUBLE(instr->counter);

    instr->startup += instr->firsttuple;
    instr->total += totaltime;
    instr->ntuples += instr->tuplecount;
    instr->nloops += 1;

    /* Reset for next cycle (if any) */
    instr->running = false;
    INSTR_TIME_SET_ZERO(instr->starttime);
    INSTR_TIME_SET_ZERO(instr->counter);
    instr->firsttuple = 0;
    instr->tuplecount = 0;
}

/* dst += add - sub */
static void
BufferUsageAccumDiff(BufferUsage *dst,
                     const BufferUsage *add,
                     const BufferUsage *sub)
{
    dst->shared_blks_hit += add->shared_blks_hit - sub->shared_blks_hit;
    dst->shared_blks_read += add->shared_blks_read - sub->shared_blks_read;
    dst->shared_blks_dirtied += add->shared_blks_dirtied - sub->shared_blks_dirtied;
    dst->shared_blks_written += add->shared_blks_written - sub->shared_blks_written;
    dst->local_blks_hit += add->local_blks_hit - sub->local_blks_hit;
    dst->local_blks_read += add->local_blks_read - sub->local_blks_read;
    dst->local_blks_dirtied += add->local_blks_dirtied - sub->local_blks_dirtied;
    dst->local_blks_written += add->local_blks_written - sub->local_blks_written;
    dst->temp_blks_read += add->temp_blks_read - sub->temp_blks_read;
    dst->temp_blks_written += add->temp_blks_written - sub->temp_blks_written;
    INSTR_TIME_ACCUM_DIFF(dst->blk_read_time,
                          add->blk_read_time, sub->blk_read_time);
    INSTR_TIME_ACCUM_DIFF(dst->blk_write_time,
                          add->blk_write_time, sub->blk_write_time);
}