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Sabbiolina

Member

Registered: 2014-05-20

Posts: 120

[mongodb] FindONe clarification

I thought that the two lines of code are equivalent, however it seems that the first is not interpreted correctly, the call does not return.

    doc:=Coll.FindDoc('{Name:?}',['{"$regex": "test.*", $options: "i"}']); // infinite loop 

    doc:=Coll.FindDoc('{Name:{"$regex": "test.*", $options: "i"}}',[]); // ok

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,661

Website

Re: [mongodb] FindONe clarification

You are confusing {Name:?}  and {Name:%}
{Name:?} means that ? will be replaced by a value - and here your value is a string, not an object.

FindDoc('{Name:?}',['{"$regex": "test.*", $options: "i"}'])

will search for

{Name:"{\"$regex\": \"test.*\", $options: \"i\"}"}

Which is not the same as

FindDoc('{Name:{"$regex": "test.*", $options: "i"}}',[])

You may write:

FindDoc('{Name:?}',[BSONVariant('{"$regex": "test.*", $options: "i"}')])

to search for an object.

But there is no benefit at all in respect to "pure JSON"

FindDoc('{Name:{"$regex": "test.*", $options: "i"}}',[])

But the fact that there is an infinite loop is not expected.
It should return no match, not loop.
Where in the code does it loop for ever?

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,661

Website

Re: [mongodb] FindONe clarification

AFAIK the easiest is to use directly the MongoDB extended syntax, which is handled by our unit at BSONVariant level:

FindDoc('{Name:/test.*/i}',[]);

Sounds better, no?

Sabbiolina

Member

Registered: 2014-05-20

Posts: 120

Re: [mongodb] FindONe clarification

    doc:=Coll.FindDoc('{Name:%}',['"$regex": "test.*", $options: "i"']); 

function TBSONWriter.BSONWriteDocFromJSON(JSON: PUTF8Char; aEndOfObject: PUTF8Char;
  out Kind: TBSONElementType; DoNotTryExtendedMongoSyntax: boolean): PUTF8Char;

in this point:

 '{': begin
    Kind := betDoc;
    Start := BSONDocumentBegin;
    repeat inc(JSON) until not(JSON^ in [#1..' ']);
    repeat
      // see http://docs.mongodb.org/manual/reference/mongodb-extended-json
      Name := GetJSONPropName(JSON); // BSON/JSON accepts "" as key name
      BSONWriteFromJSON(Name,JSON,@EndOfObject,DoNotTryExtendedMongoSyntax);
      if (JSON=nil) or (EndOfObject=#0) then
        exit; // invalid content
    until EndOfObject='}';
  end;

EndOfObject is always ':'

Last edited by Sabbiolina (2014-05-22 07:55:26)

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 14,661

Website

Re: [mongodb] FindONe clarification

Your expression is not valid JSON at all.

doc:=Coll.FindDoc('{Name:%}',['"$regex": "test.*", $options: "i"']); 

Will try to parse ('{Name:%}'

Sabbiolina

Member

Registered: 2014-05-20

Posts: 120

Re: [mongodb] FindONe clarification

You are absolutely right.

But I'm a little concerned by the queries dynamically created with parts supplied by the user.

there is some function of input validation in this fantastic library?

Sabbiolina

Member

Registered: 2014-05-20

Posts: 120

Re: [mongodb] FindONe clarification

Update. This is the string that blocks the parser:

doc:=Coll.FindDoc('{Name:?}',['{"$regex": "test.*", $options: "i"}']);

Your first

Sabbiolina

Member

Registered: 2014-05-20

Posts: 120

Re: [mongodb] FindONe clarification

after formatUTF8:

'{Name:"{""$regex"": ""test.*"", $options: ""i""}"}'