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Sybil
Asked: 2017-05-24 07:36:30 +0800 CST

什么是“planSummary：IDHACK”？

  • 772

此查询仅扫描一份文档并仅返回一份文档。但这很慢：

2017-05-22T07:13:24.548+0000 I COMMAND [conn40] query databasename.collectionname query: { _id: ObjectId('576d4ce3f2d62a001e84a9b8') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8009ms
2017-05-22T07:13:24.549+0000 I COMMAND [conn10] query databasename.collectionname query: { _id: ObjectId('576d4db35de5fa001ebdd77a') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8010ms
2017-05-22T07:13:24.553+0000 I COMMAND [conn47] query databasename.collectionname query: { _id: ObjectId('576d44b7ea8351001ea5fb22') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8014ms
2017-05-22T07:13:24.555+0000 I COMMAND [conn52] query databasename.collectionname query: { _id: ObjectId('576d457ceb82a0001e205bfa') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8015ms
2017-05-22T07:13:24.555+0000 I COMMAND [conn41] query databasename.collectionname query: { _id: ObjectId('576d457ec0697c001e1e1779') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8015ms
2017-05-22T07:13:24.555+0000 I COMMAND [conn39] query databasename.collectionname query: { _id: ObjectId('576d44b8ea8351001ea5fb27') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8015ms
2017-05-22T07:13:24.561+0000 I COMMAND [conn34] query databasename.collectionname query: { _id: ObjectId('576d44b55de5fa001ebdd31e') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8022ms
2017-05-22T07:13:24.564+0000 I COMMAND [conn32] query databasename.collectionname query: { _id: ObjectId('576d4df6d738a7001ef2a235') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8025ms
2017-05-22T07:13:24.564+0000 I COMMAND [conn51] query databasename.collectionname query: { _id: ObjectId('576d48165de5fa001ebdd55a') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8024ms
2017-05-22T07:13:24.564+0000 I COMMAND [conn17] query databasename.collectionname query: { _id: ObjectId('576d44c19f2382001e953717') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8025ms
2017-05-22T07:13:24.564+0000 I COMMAND [conn8] query databasename.collectionname query: { _id: ObjectId('576d45d256c22e001efdb382') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8025ms
2017-05-22T07:13:24.564+0000 I COMMAND [conn42] query databasename.collectionname query: { _id: ObjectId('576d44bd57c75e001e6e2302') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8025ms
2017-05-22T07:13:24.564+0000 I COMMAND [conn6] query databasename.collectionname query: { _id: ObjectId('576d44b394e731001e7cd530') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8025ms
2017-05-22T07:13:24.571+0000 I COMMAND [conn31] query databasename.collectionname query: { _id: ObjectId('576d4dbcb7289f001e64e32b') } planSummary: IDHACK ntoskip:0 keysExamined:1 docsExamined:1 idhack:1 cursorExhausted:1 keyUpdates:0 writeConflicts:0 numYields:0 nreturned:1 reslen:42 locks:{ Global: { acquireCount: { r: 2 } }, Database: { acquireCount: { r: 1 } }, Collection: { acquireCount: { r: 1 } } } 8032ms

这看起来像非常慢的磁盘 I/O。是什么planSummary: IDHACK意思？还有更多信息IDHACK吗？

explain mongodb

1 个回答

  1. Best Answer

    它只是通知 mongod 已选择使用_id索引。

    更具体地说：IDHACK意味着对于所需索引支持的查询形状，绕过了正常的查询计划路径（评估、缓存、重新评估） 。这是针对按主键获取文档的常见用例的性能优化。{_id: <value>}_id

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