1. MongoDB
id:matsuou1

2. !
!
!
!
!
! Tips
!

3. ! ID matsuou1
!
!
!
!
! Oracle PostgreSQL
! MongoDB Hadoop R

4. 1.
2.
3.
4.

6. !
! RDBMS
!

7. !
!

8. MongoDB
!
! CPU
!
! JOIN
!

9. •
• 100 insert update delete
•
• nscanned 10
•

10. db/queryoptimizer.cpp

12. ! explain
> db.logs.find({uid:"a10Sty5jqqiyxxxx2"}).explain();
{
"cursor" : "BasicCursor",
"nscanned" : 2669511,
"nscannedObjects" : 2669511,
"n" : 3,
"millis" : 6100,
"nYields" : 0,
"nChunkSkips" : 0,
"isMultiKey" : false,
"indexOnly" : false,
"indexBounds" : {
}
}

13. cursor
BasicCursor
BasicCursor or BtreeCursor
nscanned
14
nscannedObjects
14
n
14
millis
9
ms
nYields
0
nChunkSkips
0
Chunk
isMultiKey
false
indexOnly
false
indexBounds
scanAndOrder
allPlans

14. ( )
> db.logs.find({uid:"a10Sty5jqqiyxxxx2"}).explain();
{
"cursor" : "BasicCursor",
"nscanned" : 2669511,
"nscannedObjects" : 2669511,
"n" : 3,
"millis" : 6100,
"nYields" : 0, 6100ms
"nChunkSkips" : 0, 3 266
"isMultiKey" : false,
"indexOnly" : false,
"indexBounds" : {
}
}

15. ( )
> db.logs.find({uid:"b3iVxMGIEc3xxxxY"}).explain();
{
"cursor" : "BtreeCursor uid_1",
"nscanned" : 3,
"nscannedObjects" : 3,
"n" : 3,
"millis" : 6,
”uid_1”
"nYields" : 0, 6ms
"nChunkSkips" : 0,
3 3
"isMultiKey" : false,
"indexOnly" : false,
"indexBounds" : {
"uid" : [
[
"b3iVxMGIEc3xxxxY",
"b3iVxMGIEc3xxxxY"
]
]
}
}

17. !
! slowms
!
! db.setProfilingLevel(level,slowms)
!

18. slowms
! mongod slowms
ms
mongod
mongod --logpath=/var/log/mongodb/mongodb.log --logappend –slowms 500
Sat May 14 02:25:53 [conn16] query logdb.$cmd ntoreturn:1
command: { count: "logs", query: { path: "/index.html" }, fields: {} } reslen:64 3116ms

19. setProfilingLevel
setProfilingLevel
(level,slowms)
> db.setProfilingLevel(1,500);
{ "was" : 1, "slowms" : 100, "ok" : 1 }
100ms

20. setProfilingLevel
system.profile
> db.system.profile.find();
{ "ts" : ISODate("2011-05-01T03:40:04.462Z"), "info" : "query logdb.logs reslen:192
nscanned:2669511 nquery: { uid: "b2kwyYCXn3b5Scpr" } nreturned:1 6686ms",
"millis" : 6686 }
ts
millis
info
query
query
query
nscanned
reslen
nreturned

21. db.currentOp
opid
ID KillOp
op
query update
ns
query
lockType
waitingForLock
client
desc

22. > db.currentOp();
{
"inprog" : [
{
"opid" : 272,
"active" : true,
"lockType" : "read",
"waitingForLock" : false,
"secs_running" : 20,
"op" : "query",
"ns" : "logdb.logs",
"query" : {
"count" : "logs",
"query" : {
"month" : "2010/02"
},
"fields" : {
}
},
"client" : "127.0.0.1:59394",
"desc" : "conn"
}]}

23. slowms
db.setProfilingLevel
collection system.profile capped collection
db.currentOp
MongoDB

24. Tips

25. !
• db.c.find( {x:10,y:20} ), using index {x:1,y:1}
• db.c.find( {x:10,y:20} ), using index {x:1,y:-1}
• db.c.find( {x:{$in:[10,20]},y:20} ), using index {x:1,y:1}
• db.c.find().sort( {x:1,y:1} ), using index {x:1,y:1}
• db.c.find().sort( {x:-1,y:1} ), using index {x:1,y:-1}
• db.c.find( {x:10} ).sort( {y:1} ), using index {x: 1,y:1}

26. hint
! hint
!

27. hint
> db.logs.find({uid:"f2RNwtj34m3xxxxB" , path : "/index.html"}).hint({uid:1}).explain();
{
"cursor" : "BtreeCursor uid_1",
"nscanned" : 95,
"nscannedObjects" : 95,
"n" : 35,
"millis" : 3,
"nYields" : 0,
"nChunkSkips" : 0,
"isMultiKey" : false,
"indexOnly" : false,
"indexBounds" : {
"uid" : [
[
"f2RNwtj34m3xxxxB",
"f2RNwtj34m3xxxxB"
]
]
}
}

28. hint
> db.logs.find({uid:"f2RNwtj34m3xxxxB" , path : "/index.html"}).hint({uid:1 , path:1}).explain();
{
"cursor" : "BtreeCursor uid_1_path_1",
"nscanned" : 35,
"nscannedObjects" : 35,
"n" : 35,
"millis" : 0,
"nYields" : 0,
"nChunkSkips" : 0,
"isMultiKey" : false,
"indexOnly" : false,
"indexBounds" : {
"uid" : [
[
"f2RNwtj34m3xxxxB",
"f2RNwtj34m3xxxxB"
]
],
( )
}
}

29. mongostat
mongostat

30. mongostat
inserts
insert /
query
query /
update
update /
delete
delete /
getmore
getmore /
command
command /
flushes
fsync flush /
mapped
Map MB
visze
MB
res
MB
faults
/
locked
Idx miss
qr|qw
read | write
ar|aw
read | write
netIn
In bits
netOut
Out bits
conn

31. collection
! getIndexKeys()
> db.logs.getIndexKeys();
[ { "_id" : 1 }, { "uid" : 1 }, { "uid" : 1, "path" : 1 } ]

32. ! db.currentOp opid db.killOp(opid)
> db.currentOp();
{
"inprog" : [
{
"opid" : 308,
"active" : true,
"lockType" : "read",
"waitingForLock" : false,
"secs_running" : 11,
"op" : "query",
"ns" : "logdb.logs",
( )
}
]
}
> db.killOp(308);
{ "info" : "attempting to kill op" }

33. !
!
! explain
!
! slowms
! setProfilingLevel
! db.currentOP
! Tips
!
! Hint
! mongostat