我收集了104444219条记录，当我执行完全扫描收集时，查询需要大约38038毫秒
db.ORDER_MASTER.find()
但在使用$where子句
db.ORDER_DETALS.find({ "$where" : "this.GLB_ROOT_ORDER_ID == this.SYS_ORDER_ID"})
此外，我们在GLB_ROOT_ORDER_ID和SYS_ORDER_ID上有索引，在同一个集合上，在检查完全扫描的两个查询的解释计划时需要2064391毫秒，但为什么执行时间有差异？
$where条款是否有其他选择？
对于
db.ORDER_MASTER.find({ "$where" : "obj.GLB_ROOT_ORDER_ID == obj.SYS_ORDER_ID"})
解释结果
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "uat_test.ORDER_MASTER",
"indexFilterSet" : false,
"parsedQuery" : {
"$where" : "obj.GLB_ROOT_ORDER_ID == obj.SYS_ORDER_ID"
},
"winningPlan" : {
"stage" : "COLLSCAN",
"filter" : {
"$where" : "obj.GLB_ROOT_ORDER_ID == obj.SYS_ORDER_ID"
},
"direction" : "forward"
},
"rejectedPlans" : [ ]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 93366348,
"executionTimeMillis" : 2064391,
"totalKeysExamined" : 0,
"totalDocsExamined" : 104444219,
"executionStages" : {
"stage" : "COLLSCAN",
"filter" : {
"$where" : "obj.GLB_ROOT_ORDER_ID == obj.SYS_ORDER_ID"
},
"nReturned" : 93366348,
"executionTimeMillisEstimate" : 2007680,
"works" : 104444221,
"advanced" : 93366348,
"needTime" : 11077872,
"needFetch" : 0,
"saveState" : 816961,
"restoreState" : 816961,
"isEOF" : 1,
"invalidates" : 0,
"direction" : "forward",
"docsExamined" : 104444219
}
},
"ok" : 1
}
对于
db.ORDER_MASTER.find()
解释结果
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "uat_test.ORDER_MASTER",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [ ]
},
"winningPlan" : {
"stage" : "COLLSCAN",
"filter" : {
"$and" : [ ]
},
"direction" : "forward"
},
"rejectedPlans" : [ ]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 104444219,
"executionTimeMillis" : 38038,
"totalKeysExamined" : 0,
"totalDocsExamined" : 104444219,
"executionStages" : {
"stage" : "COLLSCAN",
"filter" : {
"$and" : [ ]
},
"nReturned" : 104444219,
"executionTimeMillisEstimate" : 26520,
"works" : 104444221,
"advanced" : 104444219,
"needTime" : 1,
"needFetch" : 0,
"saveState" : 815970,
"restoreState" : 815970,
"isEOF" : 1,
"invalidates" : 0,
"direction" : "forward",
"docsExamined" : 104444219
}
},
"ok" : 1
}