|
Reproducer:
var tags = [ 'a','b','c','d'];
|
db.test.ensureIndex( { tags : 1, string : 1} )
|
for(x=0;x<1000000;x++){
|
var tg = [];
|
for(t=0;t<Math.floor(Math.random()*10);t++){tg.push(tags[x%4]+t)}
|
db.test.insert( { tags : tg, string : tags[x%4] })
|
}
|
db.test.find( { tags : "b0", string : "b" } ).explain(verbose="executionStats")
|
When running the above code, the find will take twice as long under WT as it does on MMv1.
Logs from WT
2015-06-04T16:37:36.363+1000 I QUERY [conn3] query test.test query: { query: { tags: "b0", string: "b" }, $explain: true } ntoreturn:0 ntoskip:0 keyUpdates:0 writeConflicts:0 numYields:1934 reslen:1517 locks:{ Global: { acquireCount: { r: 3870 } }, Database: { acquireCount: { r: 1935 } }, Collection: { acquireCount: { r: 1935 } } } 603ms
|
2015-06-04T16:37:36.893+1000 I QUERY [conn3] query test.test query: { query: { tags: "b0", string: "b" }, $explain: true } ntoreturn:0 ntoskip:0 keyUpdates:0 writeConflicts:0 numYields:1934 reslen:1517 locks:{ Global: { acquireCount: { r: 3870 } }, Database: { acquireCount: { r: 1935 } }, Collection: { acquireCount: { r: 1935 } } } 526ms
|
2015-06-04T16:37:38.330+1000 I QUERY [conn3] query test.test query: { query: { tags: "b0", string: "b" }, $explain: true } ntoreturn:0 ntoskip:0 keyUpdates:0 writeConflicts:0 numYields:1934 reslen:1517 locks:{ Global: { acquireCount: { r: 3870 } }, Database: { acquireCount: { r: 1935 } }, Collection: { acquireCount: { r: 1935 } } } 490ms
|
2015-06-04T16:37:39.602+1000 I QUERY [conn3] query test.test query: { query: { tags: "b0", string: "b" }, $explain: true } ntoreturn:0 ntoskip:0 keyUpdates:0 writeConflicts:0 numYields:1934 reslen:1517 locks:{ Global: { acquireCount: { r: 3870 } }, Database: { acquireCount: { r: 1935 } }, Collection: { acquireCount: { r: 1935 } } } 490ms
|
2015-06-04T16:37:40.484+1000 I QUERY [conn3] query test.test query: { query: { tags: "b0", string: "b" }, $explain: true } ntoreturn:0 ntoskip:0 keyUpdates:0 writeConflicts:0 numYields:1934 reslen:1517 locks:{ Global: { acquireCount: { r: 3870 } }, Database: { acquireCount: { r: 1935 } }, Collection: { acquireCount: { r: 1935 } } } 493ms
|
Logs from MMv1
2015-06-04T16:38:53.158+1000 I QUERY [conn1] query test.test query: { query: { tags: "b0", string: "b" }, $explain: true } ntoreturn:0 ntoskip:0 keyUpdates:0 writeConflicts:0 numYields:2159 reslen:1517 locks:{ Global: { acquireCount: { r: 4320 } }, MMAPV1Journal: { acquireCount: { r: 2160 } }, Database: { acquireCount: { r: 2160 } }, Collection: { acquireCount: { R: 2160 } } } 536ms
|
2015-06-04T16:38:53.542+1000 I QUERY [conn1] query test.test query: { query: { tags: "b0", string: "b" }, $explain: true } ntoreturn:0 ntoskip:0 keyUpdates:0 writeConflicts:0 numYields:2110 reslen:1517 locks:{ Global: { acquireCount: { r: 4222 } }, MMAPV1Journal: { acquireCount: { r: 2111 } }, Database: { acquireCount: { r: 2111 } }, Collection: { acquireCount: { R: 2111 } } } 287ms
|
2015-06-04T16:38:54.520+1000 I QUERY [conn1] query test.test query: { query: { tags: "b0", string: "b" }, $explain: true } ntoreturn:0 ntoskip:0 keyUpdates:0 writeConflicts:0 numYields:2110 reslen:1517 locks:{ Global: { acquireCount: { r: 4222 } }, MMAPV1Journal: { acquireCount: { r: 2111 } }, Database: { acquireCount: { r: 2111 } }, Collection: { acquireCount: { R: 2111 } } } 289ms
|
2015-06-04T16:38:55.278+1000 I QUERY [conn1] query test.test query: { query: { tags: "b0", string: "b" }, $explain: true } ntoreturn:0 ntoskip:0 keyUpdates:0 writeConflicts:0 numYields:2110 reslen:1517 locks:{ Global: { acquireCount: { r: 4222 } }, MMAPV1Journal: { acquireCount: { r: 2111 } }, Database: { acquireCount: { r: 2111 } }, Collection: { acquireCount: { R: 2111 } } } 295ms
|
2015-06-04T16:38:56.008+1000 I QUERY [conn1] query test.test query: { query: { tags: "b0", string: "b" }, $explain: true } ntoreturn:0 ntoskip:0 keyUpdates:0 writeConflicts:0 numYields:2110 reslen:1517 locks:{ Global: { acquireCount: { r: 4222 } }, MMAPV1Journal: { acquireCount: { r: 2111 } }, Database: { acquireCount: { r: 2111 } }, Collection: { acquireCount: { R: 2111 } } } 282ms
|
|