mirror of https://gitee.com/bigwinds/arangodb
75 lines
1.9 KiB
Markdown
75 lines
1.9 KiB
Markdown
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@brief constructs a query-by-example for a collection
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`collection.byExample(example)`
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Fetches all documents from a collection that match the specified
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example and returns a cursor.
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You can use *toArray*, *next*, or *hasNext* to access the
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result. The result can be limited using the *skip* and *limit*
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operator.
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An attribute name of the form *a.b* is interpreted as attribute path,
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not as attribute. If you use
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*{ a : { c : 1 } }*
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as example, then you will find all documents, such that the attribute
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*a* contains a document of the form *{c : 1 }*. For example the document
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*{ a : { c : 1 }, b : 1 }*
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will match, but the document
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*{ a : { c : 1, b : 1 } }*
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will not.
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However, if you use
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*{ a.c : 1 }*,
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then you will find all documents, which contain a sub-document in *a*
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that has an attribute *c* of value *1*. Both the following documents
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*{ a : { c : 1 }, b : 1 }* and
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*{ a : { c : 1, b : 1 } }*
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will match.
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`collection.byExample(path1, value1, ...)`
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As alternative you can supply an array of paths and values.
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@EXAMPLES
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Use *toArray* to get all documents at once:
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@EXAMPLE_ARANGOSH_OUTPUT{003_collectionByExample}
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~ db._create("users");
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db.users.save({ name: "Gerhard" });
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db.users.save({ name: "Helmut" });
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db.users.save({ name: "Angela" });
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db.users.all().toArray();
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db.users.byExample({ "_id" : "users/20" }).toArray();
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db.users.byExample({ "name" : "Gerhard" }).toArray();
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db.users.byExample({ "name" : "Helmut", "_id" : "users/15" }).toArray();
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~ db._drop("users");
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@END_EXAMPLE_ARANGOSH_OUTPUT
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Use *next* to loop over all documents:
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@EXAMPLE_ARANGOSH_OUTPUT{004_collectionByExampleNext}
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~ db._create("users");
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db.users.save({ name: "Gerhard" });
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db.users.save({ name: "Helmut" });
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db.users.save({ name: "Angela" });
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var a = db.users.byExample( {"name" : "Angela" } );
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while (a.hasNext()) print(a.next());
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~ db._drop("users");
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@END_EXAMPLE_ARANGOSH_OUTPUT
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