#!/bin/bash

trap "rm -f /tmp/$$" 0 1 2 3 15

BLCKSZ=8192

if [ "$RANDOM" = "$RANDOM" ]
then	echo "Your shell does not support \$RANDOM.  Try using bash." 1>&2
	exit 1
fi

# XXX We assume 0 <= random <= 32767

echo "Collecting sizing information ..."

TEMPLATE1=`du -s "$PGDATA/base/1" | awk '{print $1}'`
FULL=`du -s "$PGDATA/base" | awk '{print $1}'`
if [ "$FULL" -lt `expr "$TEMPLATE1" \* 4` ]
then	echo "Your installation should have at least four times the data stored in template1 to yield meaningful results" 1>&2
	exit 1 
fi

find "$PGDATA/base" -type f -exec ls -ld {} \; |
awk '$5 % '"$BLCKSZ"' == 0 {print $5 / '"$BLCKSZ"', $9}' |
grep -v '^0 ' > /tmp/$$

TOTAL=`awk 'BEGIN	{sum=0}
			{sum += $1}
	    END		{print sum}' /tmp/$$`

echo "Running random access timing test ..."

START=`date '+%s'`
PAGES=1000

while [ "$PAGES" -ne 0 ]
do
	BIGRAND=`expr "$RANDOM" \* 32768 + "$RANDOM"`
	
	OFFSET=`awk 'BEGIN{printf "%d\n", ('"$BIGRAND"' / 2^30) * '"$TOTAL"'}'`
	
	RESULT=`awk '	BEGIN	{offset = 0}
		offset + $1 > '"$OFFSET"' \
			{print $2, '"$OFFSET"' - offset ; exit}
			{offset += $1}' /tmp/$$`
	FILE=`echo "$RESULT" | awk '{print $1}'`
	OFFSET=`echo "$RESULT" | awk '{print $2}'`
	
	dd bs="$BLCKSZ" seek="$OFFSET" count=1 if="$FILE" of="/dev/null" >/dev/null 2>&1
	PAGES=`expr "$PAGES" - 1`
done

STOP=`date '+%s'`
RANDTIME=`expr "$STOP" - "$START"`

echo "Running sequential access timing test ..."

START=`date '+%s'`
# We run the random test 10 times more because it is quicker and
# we need it to run for a while to get accurate results.
PAGES=10000

while [ "$PAGES" -ne 0 ]
do
	BIGRAND=`expr "$RANDOM" \* 32768 + "$RANDOM"`
	
	OFFSET=`awk 'BEGIN{printf "%d\n", ('"$BIGRAND"' / 2^30) * '"$TOTAL"'}'`
	
	RESULT=`awk '	BEGIN	{offset = 0}
		offset + $1 > '"$OFFSET"' \
			{print $2, $1; exit}
			{offset += $1}' /tmp/$$`
	FILE=`echo "$RESULT" | awk '{print $1}'`
	FILEPAGES=`echo "$RESULT" | awk '{print $2}'`

	if [ "$FILEPAGES" -gt "$PAGES" ]
	then	FILEPAGES="$PAGES"
	fi
	
	dd bs="$BLCKSZ" count="$FILEPAGES" if="$FILE" of="/dev/null" >/dev/null 2>&1
	PAGES=`expr "$PAGES" - "$FILEPAGES"`
done

STOP=`date '+%s'`
SEQTIME=`expr "$STOP" - "$START"`

echo
awk 'BEGIN	{printf "random_page_cost = %f\n", ('"$RANDTIME"' / '"$SEQTIME"') * 10}'