/*-------------------------------------------------------------------------
 *
 * instrument.c
 *	 functions for instrumentation of plan execution
 *
 *
 * Copyright (c) 2001-2010, 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;

	/* timer is always required for now */
	Assert(instrument_options & INSTRUMENT_TIMER);

	instr = palloc0(n * sizeof(Instrumentation));
	if (instrument_options & INSTRUMENT_BUFFERS)
	{
		int			i;

		for (i = 0; i < n; i++)
			instr[i].needs_bufusage = true;
	}

	return instr;
}

/* Entry to a plan node */
void
InstrStartNode(Instrumentation *instr)
{
	if (INSTR_TIME_IS_ZERO(instr->starttime))
		INSTR_TIME_SET_CURRENT(instr->starttime);
	else
		elog(DEBUG2, "InstrStartNode called twice in a row");

	/* initialize buffer usage per plan node */
	if (instr->needs_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;

	if (INSTR_TIME_IS_ZERO(instr->starttime))
	{
		elog(DEBUG2, "InstrStopNode called without start");
		return;
	}

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

	INSTR_TIME_SET_ZERO(instr->starttime);

	/* Adds delta of buffer usage to node's count. */
	if (instr->needs_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(DEBUG2, "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;
}

static void
BufferUsageAccumDiff(BufferUsage *dst,
					 const BufferUsage *add,
					 const BufferUsage *sub)
{
	/* dst += add - 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_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_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;
}
