Multikey Indexes

Overview

多键索引可提高对数组值字段的查询性能。您可以使用与单字段或复合索引相同的语法来定义多键索引。

样本数据

The examples in this guide use the movies collection in the sample_mflix database from the Atlas sample datasets. To learn how to create a free MongoDB Atlas cluster and load the sample datasets, see the MongoDB Get Started guide.

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);

以下示例执行的查询使用了在前面的代码示例中创建的索引：

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、索引绑定计算和排序行为方面的行为与其他索引不同。要了解有关多键索引的更多信息，包括对其行为和限制的讨论，请参阅 MongoDB Server 手册中的多键索引指南。

API 文档

要学习；了解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：