我正在使用带有WiredTiger引擎的MongoDB 3.0.6。每天我都会在日志中看到很多慢查询。像这样：
2015-09-08T11:55:32.767+0200 I QUERY [conn157653] query assets.items query: { path: "/7ee6cceab7274515eb4b5d1de35639e6" } planSummary: IXSCAN { path: 1.0 } ntoskip:0 nscanned:1 nscannedObjects:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:84181 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 125ms
我看到此查询使用索引并执行 IXSCAN 。但它太长了。有没有可能加快这个查询？
这是我的索引统计信息：
{
"ns" : "assets.items",
"count" : 16470344,
"size" : NumberLong("1608392512147"),
"avgObjSize" : 97653,
"storageSize" : NumberLong("1564940533760"),
"capped" : false,
"wiredTiger" : {
"metadata" : {
"formatVersion" : 1
},
"creationString" : "allocation_size=4KB,app_metadata=(formatVersion=1),block_allocation=best,block_compressor=snappy,cache_resident=0,checkpoint=(WiredTigerCheckpoint.3642=(addr=\"01e31baf1b81e48318bd5ce4034d250ec09ae4db5515d1e402dbc1a4c07ee4850f23a4808080e6016c5db95fc0e601698e5abfc0\",order=3642,time=1441706190,size=1552871514112,write_gen=13958214)),checkpoint_lsn=(35558,53880320),checksum=on,collator=,columns=,dictionary=0,format=btree,huffman_key=,huffman_value=,id=2585,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,memory_page_max=10m,os_cache_dirty_max=0,os_cache_max=0,prefix_compression=0,prefix_compression_min=4,split_deepen_min_child=0,split_deepen_per_child=0,split_pct=90,value_format=u,version=(major=1,minor=1)",
"type" : "file",
"uri" : "statistics:table:assets/collection-1286-6367141254744722582",
"LSM" : {
// ...
}},
"block-manager" : {
"file allocation unit size" : 4096,
"blocks allocated" : 515519,
"checkpoint size" : NumberLong("1552871514112"),
"allocations requiring file extension" : 0,
"blocks freed" : 496562,
"file magic number" : 120897,
"file major version number" : 1,
"minor version number" : 0,
"file bytes available for reuse" : 12082257920,
"file size in bytes" : NumberLong("1564940533760")
},
"btree" : {
"btree checkpoint generation" : 1568,
"column-store variable-size deleted values" : 0,
"column-store fixed-size leaf pages" : 0,
"column-store internal pages" : 0,
"column-store variable-size leaf pages" : 0,
"pages rewritten by compaction" : 0,
"number of key/value pairs" : 0,
"fixed-record size" : 0,
"maximum tree depth" : 75,
"maximum internal page key size" : 368,
"maximum internal page size" : 4096,
"maximum leaf page key size" : 3276,
"maximum leaf page size" : 32768,
"maximum leaf page value size" : 67108864,
"overflow pages" : 0,
"row-store internal pages" : 0,
"row-store leaf pages" : 0
},
"cache" : {
"bytes read into cache" : 54305601257,
"bytes written from cache" : 28288529220,
"checkpoint blocked page eviction" : 191,
"unmodified pages evicted" : 286870,
"page split during eviction deepened the tree" : 0,
"modified pages evicted" : 275984,
"data source pages selected for eviction unable to be evicted" : 26647,
"hazard pointer blocked page eviction" : 4310,
"internal pages evicted" : 208571,
"pages split during eviction" : 891,
"in-memory page splits" : 0,
"overflow values cached in memory" : 0,
"pages read into cache" : 632202,
"overflow pages read into cache" : 0,
"pages written from cache" : 513631
},
"compression" : {
"raw compression call failed, no additional data available" : 0,
"raw compression call failed, additional data available" : 0,
"raw compression call succeeded" : 0,
"compressed pages read" : 229002,
"compressed pages written" : 149994,
"page written failed to compress" : 132842,
"page written was too small to compress" : 230793
},
"cursor" : {
"create calls" : 67,
"insert calls" : 555941,
"bulk-loaded cursor-insert calls" : 0,
"cursor-insert key and value bytes inserted" : 42986335470,
"next calls" : 0,
"prev calls" : 1,
"remove calls" : 0,
"cursor-remove key bytes removed" : 0,
"reset calls" : 2630310,
"search calls" : 2610311,
"search near calls" : 0,
"update calls" : 0,
"cursor-update value bytes updated" : 0
},
"reconciliation" : {
"dictionary matches" : 0,
"internal page multi-block writes" : 239,
"leaf page multi-block writes" : 1174,
"maximum blocks required for a page" : 68,
"internal-page overflow keys" : 0,
"leaf-page overflow keys" : 0,
"overflow values written" : 0,
"pages deleted" : 0,
"page checksum matches" : 5423,
"page reconciliation calls" : 496234,
"page reconciliation calls for eviction" : 60217,
"leaf page key bytes discarded using prefix compression" : 0,
"internal page key bytes discarded using suffix compression" : 20966
},
"session" : {
"object compaction" : 0,
"open cursor count" : 67
},
"transaction" : {
"update conflicts" : 6814
}
},
"nindexes" : 2,
"totalIndexSize" : 1008476160,
"indexSizes" : {
"_id_" : 216711168,
"path_1" : 791764992
},
"ok" : 1
}
服务器有30Gb的内存，其中一半用于我的WiredTiger缓存。似乎还不够？