Details
Minor - P4 Description
Setup: create a toy collection that has no indices:
> t = db.t
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> t.drop()
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> t.save({a: 1})
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Then, start a 2.4.x mongod with the --notablescan option:
> db.version()
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2.4.9
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> t.find({a: {$exists: true}}).explain()
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{
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"cursor" : "BasicCursor",
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...
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}
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Even though --notablescan was set, 2.4 is using a collection scan. This behavior has changed in 2.6:
> db.version()
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2.6.0
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> t.find({a: {$exists: true}}).explain()
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Wed Apr 9 10:39:16.316 error: {
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"$err" : "Unable to execute query: error processing query: ns=test.t limit=0 skip=0\nTree: a exists\nSort: {}\nProj: {}\n No query solutions",
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"code" : 17007
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} at src/mongo/shell/query.js:128
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Although the 2.6 is definitely more logical, this is a backwards breaking change that surprised at least one user (see SERVER-13520). We should doc this so it doesn't bite more users!
Attachments
Issue Links
- is related to
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SERVER-13520 The $exists operator fails if the field is not indexed when using --notablescan
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- Closed
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