by Hong Ooi
Last week, I announced AzureCosmosR, an R interface to Azure Cosmos DB, a fully-managed NoSQL database service in Azure. This post gives a short rundown on the main features of AzureCosmosR.
Explaining what Azure Cosmos DB is can be tricky, so here’s an excerpt from the official description:
Azure Cosmos DB is a fully managed NoSQL database for modern app development. Single-digit millisecond response times, and automatic and instant scalability, guarantee speed at any scale. Business continuity is assured with SLA-backed availability and enterprise-grade security. App development is faster and more productive thanks to turnkey multi region data distribution anywhere in the world, open source APIs and SDKs for popular languages. As a fully managed service, Azure Cosmos DB takes database administration off your hands with automatic management, updates and patching. It also handles capacity management with cost-effective serverless and automatic scaling options that respond to application needs to match capacity with demand.
Among other features, Azure Cosmos DB is notable in that it supports multiple data models and APIs. When you create a new Cosmos DB account, you specify which API you want to use: SQL/core API, which lets you use a dialect of T-SQL to query and manage tables and documents; MongoDB; Azure table storage; Cassandra; or Gremlin (graph). AzureCosmosR provides a comprehensive interface to the SQL API, as well as bridges to the MongoDB and table storage APIs. On the Resource Manager side, AzureCosmosR extends the AzureRMR class framework to allow creating and managing Cosmos DB accounts.
AzureCosmosR is now available on CRAN. You can also install the development version from GitHub, with devtools::install_github("Azure/AzureCosmosR").
SQL interface
The meat of AzureCosmosR is a suite of methods to work with databases, containers (tables) and documents (rows) using the SQL API.
library(dplyr)
library(AzureCosmosR)
# endpoint object for this account
endp <- cosmos_endpoint(
"https://myaccount.documents.azure.com:443/",
key="mykey"
)
# all databases in this account
list_cosmos_databases(endp)
# a specific database
db <- get_cosmos_database(endp, "mydatabase")
# create a new container and upload the Star Wars dataset from dplyr
cont <- create_cosmos_container(db, "mycontainer", partition_key="sex")
bulk_import(cont, starwars)
query_documents(cont, "select * from mycontainer")
# an array select: all characters who appear in ANH
query_documents(cont,
"select c.name
from mycontainer c
where array_contains(c.films, 'A New Hope')")You can easily create and execute JavaScript stored procedures and user-defined functions:
proc <- create_stored_procedure(
cont,
"helloworld",
'function () {
var context = getContext();
var response = context.getResponse();
response.setBody("Hello, World");
}'
)
exec_stored_procedure(proc)
create_udf(cont, "times2", "function(x) { return 2*x; }")
query_documents(cont, "select udf.times2(c.height) from cont c")Aggregates take some extra work, as the Cosmos DB REST API currently only has limited support for cross-partition queries. Set by_pkrange=TRUE in the query_documents call, which will run the query on each partition key range (physical partition) and return a list of data frames. You can then process the list to obtain an overall result.
# average height by sex, by pkrange
df_lst <- query_documents(cont,
"select c.gender, count(1) n, avg(c.height) height
from mycontainer c
group by c.gender",
by_pkrange=TRUE
)
# combine pkrange results
df_lst %>%
bind_rows(.id="pkrange") %>%
group_by(gender) %>%
summarise(height=weighted.mean(height, n))Full support for cross-partition queries, including aggregates, may come in a future version of AzureCosmosR.
Other client interfaces
MongoDB
You can query data in a MongoDB-enabled Cosmos DB instance using the mongolite package. AzureCosmosR provides a simple bridge to facilitate this.
endp <- cosmos_mongo_endpoint(
"https://myaccount.mongo.cosmos.azure.com:443/",
key="mykey"
)
# a mongolite::mongo object
conn <- cosmos_mongo_connection(endp, "mycollection", "mydatabase")
conn$find("{}")For more information on working with MongoDB, see the mongolite documentation.
Table storage
You can work with data in a table storage-enabled Cosmos DB instance using the AzureTableStor package.
endp <- AzureTableStor::table_endpoint(
"https://myaccount.table.cosmos.azure.com:443/",
key="mykey"
)
tab <- AzureTableStor::storage_table(endp, "mytable")
AzureTableStor::list_table_entities(tab, filter="firstname eq 'Satya'")Further information
A good introduction to Azure Cosmos DB can be found here, or you can browse the official documentation. If you have any questions or feedback about the AzureCosmosR package, you can open an issue or email me at hongooi73 (@) gmail.com.
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