多键索引

本页内容

概述

示例数据
创建多键索引
API 文档

概述

多键索引是针对数组值字段查询性能的改进索引。您可以使用与单个字段或复合索引相同的语法定义多键索引。

示例数据

本指南中的示例使用来自movies 集合的 sample_mflix 数据库，该数据库来自Atlas示例数据集。有关创建免费MongoDB Atlas集群和加载数据集的说明，请参阅Atlas入门指南。

创建多键索引

以下示例在cast字段上创建多键索引

bson_error_t error;
bson_t *keys = BCON_NEW ("cast", BCON_INT32 (1));
mongoc_index_model_t *index_model = mongoc_index_model_new (keys, NULL);
if (mongoc_collection_create_indexes_with_opts (collection, &index_model, 1, NULL, NULL, &error)) {
    printf ("Successfully created index\n");
} else {
    fprintf (stderr, "Failed to create index: %s", error.message);
}
bson_destroy (keys);
mongoc_index_model_destroy (index_model);

以下示例执行使用前面代码示例中创建的索引的查询

const bson_t *doc;
bson_t *filter = BCON_NEW ("cast", BCON_UTF8 ("Viola Davis"));
mongoc_cursor_t *results =
    mongoc_collection_find_with_opts (collection, filter, NULL, NULL);
while (mongoc_cursor_next (results, &doc)) {
    char *str = bson_as_canonical_extended_json (doc, NULL);
    printf ("%s\n", str);
    bson_free (str);
}
mongoc_cursor_destroy (results);
bson_destroy (filter);

{ "_id" : ..., "cast" : [ "Kelsey Grammer", "Cary Elwes", "Viola Davis", "John C. McGinley" ], "title" : "The Pentagon Wars", ... }
{ "_id" : ..., "cast" : [ "George Clooney", "Natascha McElhone", "Viola Davis", "Jeremy Davies" ], "title" : "Solaris", ... }
{ "_id" : ..., "cast" : [ "Meryl Streep", "Philip Seymour Hoffman", "Amy Adams", "Viola Davis" ], "title" : "Doubt", ... }
{ "_id" : ..., "cast" : [ "Hugh Jackman", "Jake Gyllenhaal", "Viola Davis", "Maria Bello" ], "title" : "Prisoners", ... }
{ "_id" : ..., "cast" : [ "Emma Stone", "Viola Davis", "Bryce Dallas Howard", "Octavia Spencer" ], "title" : "The Help", ... }
...

多键索引在查询覆盖、索引边界计算和排序行为方面与其他索引表现不同。有关多键索引的更多信息，包括其行为和限制的讨论，请参阅MongoDB服务器手册中的多键索引指南。

API文档

有关本指南中讨论的任何函数的更多信息，请参阅以下API文档

复合索引

Atlas 搜索索引