MongoDB:The Definitive Guide 2nd笔记之查看数据库大小

查看大小
Documents

Collections

Databases

mongo状态检测

查看大小

Documents

利用

Object.bsonsize()

计算一个文档的大小

通过例子我们可以看到_ids作为ObjectIds来存储比作为strings来存储更有效。

> Object.bsonsize({_id:ObjectId()})
22
> // ""+ObjectId() converts the ObjectId to a string
> Object.bsonsize({_id:""+ObjectId()})
39

获取数据库中某个文档的大小

> Object.bsonsize(db.users.findOne())

这个大小不包括

padding

或

indexes

的大小。

Collections

> db.books.stats()
{
"ns" : "test.books",
"count" : 6,
"size" : 368,
"avgObjSize" : 61,
"storageSize" : 36864,
"capped" : false,
"wiredTiger" : {
"metadata" : {
"formatVersion" : 1
},
"creationString" : "allocation_size=4KB,app_metadata=(formatVersion=1),block_allocation=best,block_compressor=snappy,cache_resident=0,checksum=on,colgroups=,collator=,columns=,dictionary=0,encryption=(keyid=,name=),exclusive=0,extractor=,format=btree,huffman_key=,huffman_value=,immutable=0,internal_item_max=0,internal_key_max=0,internal_key_truncate=,internal_page_max=4KB,key_format=q,key_gap=10,leaf_item_max=0,leaf_key_max=0,leaf_page_max=32KB,leaf_value_max=64MB,log=(enabled=),lsm=(auto_throttle=,bloom=,bloom_bit_count=16,bloom_config=,bloom_hash_count=8,bloom_oldest=0,chunk_count_limit=0,chunk_max=5GB,chunk_size=10MB,merge_max=15,merge_min=0),memory_page_max=10m,os_cache_dirty_max=0,os_cache_max=0,prefix_compression=0,prefix_compression_min=4,source=,split_deepen_min_child=0,split_deepen_per_child=0,split_pct=90,type=file,value_format=u",
"type" : "file",
"uri" : "statistics:table:collection-24--434149781242754711",
"LSM" : {
"bloom filter false positives" : 0,
"bloom filter hits" : 0,
"bloom filter misses" : 0,
"bloom filter pages evicted from cache" : 0,
"bloom filter pages read into cache" : 0,
"bloom filters in the LSM tree" : 0,
"chunks in the LSM tree" : 0,
"highest merge generation in the LSM tree" : 0,
"queries that could have benefited from a Bloom filter that did not exist" : 0,
"sleep for LSM checkpoint throttle" : 0,
"sleep for LSM merge throttle" : 0,
"total size of bloom filters" : 0
},
"block-manager" : {
"allocations requiring file extension" : 0,
"blocks allocated" : 8,
"blocks freed" : 2,
"checkpoint size" : 24576,
"file allocation unit size" : 4096,
"file bytes available for reuse" : 16384,
"file magic number" : 120897,
"file major version number" : 1,
"file size in bytes" : 36864,
"minor version number" : 0
},
"btree" : {
"btree checkpoint generation" : 23041,
"column-store fixed-size leaf pages" : 0,
"column-store internal pages" : 0,
"column-store variable-size RLE encoded values" : 0,
"column-store variable-size deleted values" : 0,
"column-store variable-size leaf pages" : 0,
"fixed-record size" : 0,
"maximum internal page key size" : 368,
"maximum internal page size" : 4096,
"maximum leaf page key size" : 2867,
"maximum leaf page size" : 32768,
"maximum leaf page value size" : 67108864,
"maximum tree depth" : 3,
"number of key/value pairs" : 0,
"overflow pages" : 0,
"pages rewritten by compaction" : 0,
"row-store internal pages" : 0,
"row-store leaf pages" : 0
},
"cache" : {
"bytes read into cache" : 400,
"bytes written from cache" : 921,
"checkpoint blocked page eviction" : 0,
"data source pages selected for eviction unable to be evicted" : 0,
"hazard pointer blocked page eviction" : 0,
"in-memory page passed criteria to be split" : 0,
"in-memory page splits" : 0,
"internal pages evicted" : 0,
"internal pages split during eviction" : 0,
"leaf pages split during eviction" : 0,
"modified pages evicted" : 0,
"overflow pages read into cache" : 0,
"overflow values cached in memory" : 0,
"page split during eviction deepened the tree" : 0,
"page written requiring lookaside records" : 0,
"pages read into cache" : 2,
"pages read into cache requiring lookaside entries" : 0,
"pages requested from the cache" : 20,
"pages written from cache" : 4,
"pages written requiring in-memory restoration" : 0,
"unmodified pages evicted" : 0
},
"compression" : {
"compressed pages read" : 0,
"compressed pages written" : 0,
"page written failed to compress" : 0,
"page written was too small to compress" : 4,
"raw compression call failed, additional data available" : 0,
"raw compression call failed, no additional data available" : 0,
"raw compression call succeeded" : 0
},
"cursor" : {
"bulk-loaded cursor-insert calls" : 0,
"create calls" : 5,
"cursor-insert key and value bytes inserted" : 77,
"cursor-remove key bytes removed" : 0,
"cursor-update value bytes updated" : 0,
"insert calls" : 2,
"next calls" : 39,
"prev calls" : 1,
"remove calls" : 0,
"reset calls" : 14,
"restarted searches" : 0,
"search calls" : 1,
"search near calls" : 1,
"truncate calls" : 0,
"update calls" : 0
},
"reconciliation" : {
"dictionary matches" : 0,
"fast-path pages deleted" : 0,
"internal page key bytes discarded using suffix compression" : 0,
"internal page multi-block writes" : 0,
"internal-page overflow keys" : 0,
"leaf page key bytes discarded using prefix compression" : 0,
"leaf page multi-block writes" : 0,
"leaf-page overflow keys" : 0,
"maximum blocks required for a page" : 0,
"overflow values written" : 0,
"page checksum matches" : 0,
"page reconciliation calls" : 4,
"page reconciliation calls for eviction" : 0,
"pages deleted" : 0
},
"session" : {
"object compaction" : 0,
"open cursor count" : 1
},
"transaction" : {
"update conflicts" : 0
}
},
"nindexes" : 1,
"totalIndexSize" : 36864,
"indexSizes" : {
"_id_" : 36864
},
"ok" : 1
}

Databases

> db.stats()
{
"db" : "test",
"collections" : 12,//所有collection的数目
"objects" : 25701,//所有collection的所有document的数目
"avgObjSize" : 414.88930391813545,
"dataSize" : 10663070,//数据库占用空间，不包括free list,包括padding
"storageSize" : 5005312,//数据库占用的空间
"numExtents" : 0,
"indexes" : 14,
"indexSize" : 585728,
"ok" : 1
}

在一个大型的数据库中调用这个函数会非常慢，阻塞其他操作，尽量少用。

mongo状态检测

在终端命令行下运行mongostat

~$ mongostat
insert query update delete getmore command % dirty % used flushes vsize   res qr|qw ar|aw netIn netOut conn                      time
*0    *0     *0     *0       0     1|0     0.0    0.0       0  264M 29.0M   0|0   0|0   79b  19.2k    1 2016-09-25T09:46:57+08:00
*0    *0     *0     *0       0     1|0     0.0    0.0       0  264M 29.0M   0|0   0|0   79b  19.2k    1 2016-09-25T09:46:58+08:00
*0    *0     *0     *0       0     1|0     0.0    0.0       0  264M 29.0M   0|0   0|0   79b  19.2k    1 2016-09-25T09:46:59+08:00
*0    *0     *0     *0       0     1|0     0.0    0.0       0  264M 29.0M   0|0   0|0   79b  19.2k    1 2016-09-25T09:47:00+08:00
*0    *0     *0     *0       0     1|0     0.0    0.0       0  264M 29.0M   0|0   0|0   79b  19.2k    1 2016-09-25T09:47:01+08:00

在终端命令行下运行mongotop

:~$ mongotop
2016-09-25T09:47:05.209+0800    connected to: 127.0.0.1

ns    total    read    write    2016-09-25T09:47:06+08:00
admin.system.roles      0ms     0ms      0ms
admin.system.users      0ms     0ms      0ms
admin.system.version      0ms     0ms      0ms
config.version      0ms     0ms      0ms
local.startup_log      0ms     0ms      0ms
local.system.replset      0ms     0ms      0ms
tables.books      0ms     0ms      0ms
test.articles      0ms     0ms      0ms
test.books      0ms     0ms      0ms
test.characters      0ms     0ms      0ms