Query Shapes查询形状

Matching Query Shapes匹配查询形状

The following example query shape shows specifications for a find command on the pizzaOrders collection in the default test database:以下示例查询形状显示了默认test数据库中pizzaOrders集合上find命令的规范：

find: "pizzaOrders",
filter: {
   orderDate: { $gt: ISODate( "2023-01-20T00:00:00Z" ) }
},
sort: {
   totalNumber: 1
},
$db: "test"

The example filter limits the documents to those with an order date greater than the specified date. The example has an ascending sort on the total number of pizzas ordered.示例筛选器将文档限制为订单日期大于指定日期的文档。该示例对订购的披萨总数进行升序排序。

To view the MongoDB 8.0 queryShapeHash and planCacheShapeHash hexadecimal strings, you can use the explain command.要查看MongoDB 8.0 queryShapeHash和planCacheShapeHash十六进制字符串，可以使用explain命令。

The following explain examples contain queries with the same query shape:以下explain示例包含具有相同查询形状的查询：

db.pizzaOrders.explain().find(
   { orderDate: { $gt: ISODate( "2024-05-10T05:15:35Z" ) } } ).
   sort( { totalNumber: 1 }
)

db.pizzaOrders.explain().find(
   { orderDate: { $gt: ISODate( "2024-02-05T07:07:16Z" ) } } ).
   sort( { totalNumber: 1 }
)

db.pizzaOrders.explain().find(
   { orderDate: { $gt: ISODate( "2023-03-08T08:12:25Z" ) } } ).
   sort( { totalNumber: 1 }
)

Because the query shapes are the same, the explain output has the same queryShapeHash for each of the examples, and the same planCacheShapeHash for each. For example:因为查询形状相同，所以explain输出对每个示例都有相同的queryShapeHash，对每个示例也有相同的planCacheShapeHash。例如：

queryShapeHash: 'AB8ECADEE8F0EB0F447A30744EB4813AE7E0BFEF523B0870CA10FCBC87F5D8F1'
planCacheShapeHash: '48E51110'

Different Query Shape不同的查询形状

A query has a different shape if the query has different specifications. For example, if a query has a different filter, sort, projection, namespace, or aggregation pipeline stages.如果查询具有不同的规范，则查询的形状也会不同。例如，如果查询具有不同的筛选器、排序、投影、名称空间或聚合管道阶段。

In the example in the previous section, the example sorts by the totalNumber field. If you change the query sort from totalNumber to a different field, the query has a different query shape.在上一节的示例中，该示例按totalNumber字段排序。如果将查询排序从totalNumber更改为其他字段，则查询具有不同的查询形状。

For example, sorting by pizza price changes the query shape:例如，按披萨price排序会改变查询形状：

db.pizzaOrders.explain().find(
   { orderDate: { $gt: ISODate( "2023-01-20T00:00:00Z" ) } } ).
   sort( { price: 1 }
)

Because the query shape is different from the shape in the previous section, the explain output has a different queryShapeHash from the previous example, and a different planCacheShapeHash. For example:因为查询形状与上一节中的形状不同，所以explain输出的queryShapeHash与上一个示例不同，planCacheShapeHash也不同。例如：

queryShapeHash: 'AC1ECADBE8F1EB0F417A30741AB4813BE7E0BFEF523B0870CA11FCBC87F1A8B2'
planCacheShapeHash: '31A52130'