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gocosmos

Go driver for Azure Cosmos DB SQL API which can be used with the standard database/sql package. A REST client is also included.

database/sql driver

Summary of supported SQL statements:

Statement	Syntax
Create a new database	`CREATE DATABASE [IF NOT EXISTS] <db-name>`
Change database's throughput	`ALTER DATABASE <db-name> WITH RU/MAXRU=<ru>`
Delete an existing database	`DROP DATABASE [IF EXISTS] <db-name>`
List all existing databases	`LIST DATABASES`
Create a new collection	`CREATE COLLECTION [IF NOT EXISTS] [<db-name>.]<collection-name> <WITH PK=partitionKey>`
Change collection's throughput	`ALTER COLLECTION [<db-name>.]<collection-name> WITH RU/MAXRU=<ru>`
Delete an existing collection	`DROP COLLECTION [IF EXISTS] [<db-name>.]<collection-name>`
List all existing collections in a database	`LIST COLLECTIONS [FROM <db-name>]`
Insert a new document into collection	`INSERT INTO [<db-name>.]<collection-name> ...`
Insert or replace a document	`UPSERT INTO [<db-name>.]<collection-name> ...`
Delete an existing document	`DELETE FROM [<db-name>.]<collection-name> WHERE id=<id-value>`
Update an existing document	`UPDATE [<db-name>.]<collection-name> SET ... WHERE id=<id-value>`
Query documents in a collection	`SELECT [CROSS PARTITION] ... FROM <collection-name> ... [WITH database=<db-name>]`

See supported SQL statements for details.

Azure Cosmos DB SQL API currently supports only SELECT statement. gocosmos implements other statements by translating the SQL statement to REST API calls.

Example usage:

package main

import (
	"database/sql"
	_ "github.com/btnguyen2k/gocosmos"
)

func main() {
	driver := "gocosmos"
	dsn := "AccountEndpoint=https://localhost:8081/;AccountKey=<cosmosdb-account-key>"
	db, err := sql.Open(driver, dsn)
	if err != nil {
		panic(err)
	}
	defer db.Close()
	
	_, err = db.Exec("CREATE DATABASE mydb WITH maxru=10000")
	if err != nil {
		panic(err)
	}
	
	// database "mydb" has been created successfuly
}

Data Source Name (DSN) syntax for Cosmos DB

Note: line-break is for readability only!

AccountEndpoint=<cosmosdb-endpoint>
;AccountKey=<cosmosdb-account-key>
[;TimeoutMs=<timeout-in-ms>]
[;Version=<cosmosdb-api-version>]
[;DefaultDb|Db=<db-name>]
[;AutoId=<true/false>]
[;InsecureSkipVerify=<true/false>]

AccountEndpoint: (required) endpoint to access Cosmos DB. For example, the endpoint for Azure Cosmos DB Emulator running on local is https://localhost:8081/.
AccountKey: (required) account key to authenticate.
TimeoutMs: (optional) operation timeout in milliseconds. Default value is 10 seconds if not specified.
Version: (optional) version of Cosmos DB to use. Default value is 2020-07-15 if not specified. See: https://learn.microsoft.com/rest/api/cosmos-db/#supported-rest-api-versions.
DefaultDb: (optional, available since v0.1.1) specify the default database used in Cosmos DB operations. Alias Db can also be used instead of DefaultDb.
AutoId: (optional, available since v0.1.2) see auto id session.
InsecureSkipVerify: (optional, available since v0.1.4) if true, disable CA verification for https endpoint (useful to run against test/dev env with local/docker Cosmos DB emulator).

Auto-id

Azure Cosmos DB requires each document has a unique ID that identifies the document. When creating new document, if value for the unique ID field is not supplied gocosmos is able to generate one automatically. This feature is enabled by specifying setting AutoId=true in the Data Source Name (for database/sql driver) or the connection string (for REST client). If not specified, default value is AutoId=true.

This setting is available since v0.1.2.

Known issues

GROUP BY combined with ORDER BY is not supported

Azure Cosmos DB does not support GROUP BY combined with ORDER BY yet. You will receive the following error message:

'ORDER BY' is not supported in presence of GROUP BY.

Cross-partition paging

Cross-partition paging can be done with the OFFSET...LIMIT clause. However, the query is not stable without ORDER BY. The returned results may not be consistent from query to query.

Queries that may consume a large amount of memory

These queries may consume a large amount of memory if executed against a large table:

OFFSET...LIMIT clause with big offset or limit values.
SELECT DISTINCT and SELECT DISTINCT VALUE queries.
Queries with GROUP BY clause.

REST client

See the REST.md file for details.

License

This project is licensed under the MIT License - see the LICENSE.md file for details.

Support and Contribution

Disclaimer: I am also a core maintainer of microsoft/gocosmos. Features and bug fixes are synchronized between the two projects.

This project uses GitHub Issues to track bugs and feature requests. Please search the existing issues before filing new issues to avoid duplicates. For new issues, file your bug or feature request as a new Issue.

Please create pull requests in the microsoft/gocosmos repository.

If you find this project useful, please start it.