Tables

AzureTableStor provides a table_endpoint function that is the analogue of AzureStor’s blob_endpoint, file_endpoint and adls_endpoint functions. There are methods for retrieving, creating, listing and deleting tables within the endpoint.

library(AzureTableStor)

# storage account endpoint
endp <- table_endpoint(
    "https://mystorageacct.table.core.windows.net",
    key="mykey")
# Cosmos DB w/table API endpoint
endp <- table_endpoint(
    "https://mycosmosdb.table.cosmos.azure.com:443",
    key="mykey")

create_storage_table(endp, "mytable")
list_storage_tables(endp)
tab <- storage_table(endp, "mytable")

Entities

In table storage jargon, an entity is a row in a table. The columns of the table are properties. Note that table storage does not enforce a schema; that is, individual entities in a table can have different properties. An entity is identified by its RowKey and PartitionKey properties, which must be unique for each entity.

AzureTableStor provides the following functions to work with data in a table:

• insert_table_entity: inserts a row into the table.
• update_table_entity: updates a row with new data, or inserts a new row if it doesn’t already exist.
• get_table_entity: retrieves an individual row from the table.
• delete_table_entity: deletes a row from the table.
• import_table_entities: inserts multiple rows of data from a data frame into the table.

insert_table_entity(tab, list(
    RowKey="row1",
    PartitionKey="partition1",
    firstname="Bill",
    lastname="Gates"
))

get_table_entity(tab, "row1", "partition1")

# we can import to the same table as above:
# table storage doesn't enforce a schema
import_table_entities(tab, mtcars,
    row_key=row.names(mtcars),
    partition_key=as.character(mtcars$cyl))

list_table_entities(tab)
list_table_entities(tab, filter="firstname eq 'Satya'")
list_table_entities(tab, filter="RowKey eq 'Toyota Corolla'")

Batch transactions

With the exception of import_table_entities, all of the above entity functions work on a single row of data. Table storage provides a batch execution facility, which lets you bundle up single-row operations into a single transaction that will be executed atomically. In the jargon, this is known as an entity group transaction. import_table_entities is an example of an entity group transaction: it bundles up multiple rows of data into batch jobs, which is much more efficient than sending each row individually to the server.

The create_table_operation, create_batch_transaction and do_batch_transaction functions let you perform entity group transactions. Here is an example of a simple batch insert. The actual import_table_entities function is more complex as it can also handle multiple partition keys and more than 100 rows of data.

ir <- subset(iris, Species == "setosa")

# property names must be valid C# variable names
names(ir) <- sub("\\.", "_", names(ir))

# create the PartitionKey and RowKey properties
ir$PartitionKey <- ir$Species
ir$RowKey <- sprintf("%03d", seq_len(nrow(ir)))

# generate the array of insert operations: 1 per row
ops <- lapply(seq_len(nrow(ir)), function(i)
    create_table_operation(endp, "mytable", body=ir[i, ],
                           http_verb="POST")))

# create a batch transaction and send it to the endpoint
bat <- create_batch_transaction(endp, ops)
do_batch_transaction(bat)

If you have any feedback, or to report bugs with the package, please contact me at [email protected] or open an issue on GitHub.