Details
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Task
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Status: Closed
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Major - P3
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Resolution: Fixed
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None
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None
Description
Description
Description:
Remove section about restrictions on $not and $regex on this page: https://docs.mongodb.com/manual/reference/operator/query/not/index.html
Engineering Ticket Description:
Executing the following queries I was expecting the same result but apparently they are dealt differently:
2 scenarios
- matching
nair(mongod-2.7.0-pre-) test> db.system.namespaces.find({ name:/\$/} )
{
"name": "test.data.$_id_"
}
{
"name": "test.difference.$_id_"
}
{
"name": "test.posts.$_id_"
}
{
"name": "test.kunal.$_id_"
}
{
"name": "test.maha_example.$_id_"
}
has the same result has using $regex operator
nair(mongod-2.7.0-pre-) test> db.system.namespaces.find({ name:{ $regex: "\\$"}} )
{
"name": "test.data.$_id_"
}
{
"name": "test.difference.$_id_"
}
{
"name": "test.posts.$_id_"
}
{
"name": "test.kunal.$_id_"
}
{
"name": "test.maha_example.$_id_"
}
- not matching query
nair(mongod-2.7.0-pre-) test> db.system.namespaces.find({ name: {$not: /\$/}} )
{
"name": "test.system.indexes"
}
{
"name": "test.data"
}
{
"name": "test.difference"
}
{
"name": "test.posts"
}
{
"name": "test.kunal"
}
{
"name": "test.maha_example"
}
{
"name": "test.system.profile",
"options": {
"capped": true,
"size": 1048576
}
}
But using $regex operator fails
nair(mongod-2.7.0-pre-) test> db.system.namespaces.find({ name: {$not: { $regex: "\\$"}}} )
error: {
"$err": "Can't canonicalize query: BadValue $not cannot have a regex",
"code": 17287
}
Is this the expected behaviour ? and if so why ?
Looking deeper in the code I can also see the following comment:
mongo/db/matcher/expression_parser_tree.cpp:103
...
// TODO: this seems arbitrary?
// tested in jstests/not2.js
for ( unsigned i = 0; i < theAnd->numChildren(); i++ )
if ( theAnd->getChild(i)->matchType() == MatchExpression::REGEX )
return StatusWithMatchExpression( ErrorCodes::BadValue, "$not cannot have a regex" );
...
and looking int the jstests it makes even less sense:
jstests/core/not2.js
49 check( {i:{$not:/a/}}, "b" );
50 check( {i:{$not:/(a|b)/}}, "", 0 );
51 check( {i:{$not:/a/,$regex:"a"}}, "", 0 );
52 check( {i:{$not:/aa/}}, "a", 2 );
53 fail( {i:{$not:{$regex:"a"}}} );
54 fail( {i:{$not:{$options:"a"}}} );
Scope of changes
Impact to Other Docs
MVP (Work and Date)
Resources (Scope or Design Docs, Invision, etc.)
Attachments
Issue Links
- documents
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SERVER-13779 Allow $not to be applied to $regex (currently only /regex/ syntax is allowed)
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- Closed
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