SQL Server

Streaming Download Large File to the Local Filesystem

See more Azure Cloud Storage Examples

Downloads a large file in a streaming fashion to the local filesystem. SQL Server

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    DECLARE @success int
    SELECT @success = 0

    -- Azure File Service Example: Downloads a large file to the local filesystem using a Chilkat stream.
    -- See:  https://docs.microsoft.com/en-us/rest/api/storageservices/get-file

    -- This example requires the Chilkat API to have been previously unlocked.
    -- See Global Unlock Sample for sample code.

    DECLARE @rest int
    EXEC @hr = sp_OACreate 'Chilkat.Rest', @rest OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    -- Connect to the Azure Storage Blob Service
    DECLARE @bTls int
    SELECT @bTls = 1
    DECLARE @port int
    SELECT @port = 443
    DECLARE @bAutoReconnect int
    SELECT @bAutoReconnect = 1
    -- In this example, the storage account name is "chilkat".
    EXEC sp_OAMethod @rest, 'Connect', @success OUT, 'chilkat.file.core.windows.net', @port, @bTls, @bAutoReconnect
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @rest
        RETURN
      END

    -- Provide Azure Cloud credentials for the REST calls.
    DECLARE @azAuth int
    EXEC @hr = sp_OACreate 'Chilkat.AuthAzureStorage', @azAuth OUT

    EXEC sp_OASetProperty @azAuth, 'AccessKey', 'AZURE_ACCESS_KEY'
    -- The account name used here should match the 1st part of the domain passed in the call to Connect (above).
    EXEC sp_OASetProperty @azAuth, 'Account', 'chilkat'
    EXEC sp_OASetProperty @azAuth, 'Scheme', 'SharedKey'
    EXEC sp_OASetProperty @azAuth, 'Service', 'File'
    -- This causes the "x-ms-version: 2021-08-06" header to be automatically added.
    EXEC sp_OASetProperty @azAuth, 'XMsVersion', '2021-08-06'
    EXEC sp_OAMethod @rest, 'SetAuthAzureStorage', @success OUT, @azAuth

    -- Note: The application does not need to explicitly set the following
    -- headers: x-ms-date, Authorization.  These headers
    -- are automatically set by Chilkat.

    -- When streaming a download to the local filesystem or directed elsewhere,
    -- the complete HTTP GET operation must be broken into parts.
    -- For example, an HTTP GET consists of sending the request, followed by reading the response header,
    -- and then finally the response body.  We'll want to read the response header, and then based
    -- on the information received (such as success or failure), either read the response body
    -- as an error message, or as the file data.

    -- Send the HTTP GET request to download the file.
    -- The share is named "pip".
    EXEC sp_OAMethod @rest, 'SendReqNoBody', @success OUT, 'GET', '/pip/somethingBig.zip'
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @rest
        EXEC @hr = sp_OADestroy @azAuth
        RETURN
      END

    -- Read the response header.
    DECLARE @responseStatusCode int
    EXEC sp_OAMethod @rest, 'ReadResponseHeader', @responseStatusCode OUT
    IF @responseStatusCode < 0
      BEGIN
        EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @rest
        EXEC @hr = sp_OADestroy @azAuth
        RETURN
      END


    PRINT 'Response status code = ' + @responseStatusCode

    -- We expect a 200 response status if the file data is coming.
    -- Otherwise, we'll get a string response body with an error message(or no response body).
    IF @responseStatusCode = 200
      BEGIN

        DECLARE @bodyStream int
        EXEC @hr = sp_OACreate 'Chilkat.Stream', @bodyStream OUT

        -- The stream's sink will be a file.
        EXEC sp_OASetProperty @bodyStream, 'SinkFile', 'qa_output/somethingBig.zip'

        -- Read the response body to the stream.  Given that we've
        -- set the stream's sink to a file, it will stream directly
        -- to the file.
        EXEC sp_OAMethod @rest, 'ReadRespBodyStream', @success OUT, @bodyStream, 1
        IF @success <> 1
          BEGIN
            EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
            PRINT @sTmp0
            EXEC @hr = sp_OADestroy @rest
            EXEC @hr = sp_OADestroy @azAuth
            EXEC @hr = sp_OADestroy @bodyStream
            RETURN
          END


        PRINT 'Successfully received the large file.'

      END
    ELSE
      BEGIN
        DECLARE @errResponse nvarchar(4000)
        EXEC sp_OAMethod @rest, 'ReadRespBodyString', @errResponse OUT
        EXEC sp_OAGetProperty @rest, 'LastMethodSuccess', @iTmp0 OUT
        IF @iTmp0 <> 1
          BEGIN
            EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
            PRINT @sTmp0
          END
        ELSE
          BEGIN

            PRINT @errResponse
          END
      END

    EXEC @hr = sp_OADestroy @rest
    EXEC @hr = sp_OADestroy @azAuth
    EXEC @hr = sp_OADestroy @bodyStream


END
GO