SQL Server
SQL Server
HTTP Download in Parallel with Simultaneous Range Requests
See more HTTP Examples
Demonstrates how to download a large file with parallel simultaneous requests, where each request downloads a segment (range) of the remote file.Chilkat SQL Server Downloads
-- 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
-- This requires the Chilkat API to have been previously unlocked.
-- See Global Unlock Sample for sample code.
DECLARE @http int
EXEC @hr = sp_OACreate 'Chilkat.Http', @http OUT
IF @hr <> 0
BEGIN
PRINT 'Failed to create ActiveX component'
RETURN
END
-- First get the size of the file to be downloaded.
DECLARE @url nvarchar(4000)
SELECT @url = 'https://www.chilkatsoft.com/hamlet.xml'
DECLARE @resp int
EXEC @hr = sp_OACreate 'Chilkat.HttpResponse', @resp OUT
EXEC sp_OAMethod @http, 'HttpNoBody', @success OUT, 'HEAD', @url, @resp
IF @success = 0
BEGIN
EXEC sp_OAGetProperty @http, 'LastErrorText', @sTmp0 OUT
PRINT @sTmp0
EXEC @hr = sp_OADestroy @http
EXEC @hr = sp_OADestroy @resp
RETURN
END
DECLARE @remoteFileSize int
EXEC sp_OAGetProperty @resp, 'ContentLength', @remoteFileSize OUT
PRINT 'Downloading ' + @remoteFileSize + ' bytes...'
-- Let's download in 4 chunks.
-- (the last chunk will be whatever remains after the 1st 3 equal sized chunks)
DECLARE @chunkSize int
SELECT @chunkSize = @remoteFileSize / 4
-- The Range header is used to download a range from a resource
-- Range: bytes=<range-start>-<range-end>
-- or
-- Range: bytes=<range-start>-
-- We're writing code this way for clarity..
DECLARE @http1 int
EXEC @hr = sp_OACreate 'Chilkat.Http', @http1 OUT
DECLARE @http2 int
EXEC @hr = sp_OACreate 'Chilkat.Http', @http2 OUT
DECLARE @http3 int
EXEC @hr = sp_OACreate 'Chilkat.Http', @http3 OUT
DECLARE @http4 int
EXEC @hr = sp_OACreate 'Chilkat.Http', @http4 OUT
DECLARE @sbRange int
EXEC @hr = sp_OACreate 'Chilkat.StringBuilder', @sbRange OUT
EXEC sp_OAMethod @sbRange, 'SetString', @success OUT, 'bytes=<range-start>-<range-end>'
DECLARE @numReplaced int
EXEC sp_OAMethod @sbRange, 'ReplaceI', @numReplaced OUT, '<range-start>', 0
EXEC sp_OAMethod @sbRange, 'ReplaceI', @numReplaced OUT, '<range-end>', @chunkSize - 1
EXEC sp_OAMethod @sbRange, 'GetAsString', @sTmp0 OUT
PRINT @sTmp0
EXEC sp_OAMethod @sbRange, 'GetAsString', @sTmp0 OUT
EXEC sp_OAMethod @http1, 'SetRequestHeader', NULL, 'Range', @sTmp0
EXEC sp_OAMethod @sbRange, 'SetString', @success OUT, 'bytes=<range-start>-<range-end>'
EXEC sp_OAMethod @sbRange, 'ReplaceI', @numReplaced OUT, '<range-start>', @chunkSize
EXEC sp_OAMethod @sbRange, 'ReplaceI', @numReplaced OUT, '<range-end>', 2 * @chunkSize - 1
EXEC sp_OAMethod @sbRange, 'GetAsString', @sTmp0 OUT
PRINT @sTmp0
EXEC sp_OAMethod @sbRange, 'GetAsString', @sTmp0 OUT
EXEC sp_OAMethod @http2, 'SetRequestHeader', NULL, 'Range', @sTmp0
EXEC sp_OAMethod @sbRange, 'SetString', @success OUT, 'bytes=<range-start>-<range-end>'
EXEC sp_OAMethod @sbRange, 'ReplaceI', @numReplaced OUT, '<range-start>', 2 * @chunkSize
EXEC sp_OAMethod @sbRange, 'ReplaceI', @numReplaced OUT, '<range-end>', 3 * @chunkSize - 1
EXEC sp_OAMethod @sbRange, 'GetAsString', @sTmp0 OUT
PRINT @sTmp0
EXEC sp_OAMethod @sbRange, 'GetAsString', @sTmp0 OUT
EXEC sp_OAMethod @http3, 'SetRequestHeader', NULL, 'Range', @sTmp0
EXEC sp_OAMethod @sbRange, 'SetString', @success OUT, 'bytes=<range-start>-'
EXEC sp_OAMethod @sbRange, 'ReplaceI', @numReplaced OUT, '<range-start>', 3 * @chunkSize
EXEC sp_OAMethod @sbRange, 'GetAsString', @sTmp0 OUT
PRINT @sTmp0
EXEC sp_OAMethod @sbRange, 'GetAsString', @sTmp0 OUT
EXEC sp_OAMethod @http4, 'SetRequestHeader', NULL, 'Range', @sTmp0
-- Start each range download
DECLARE @task1 int
EXEC sp_OAMethod @http1, 'DownloadAsync', @task1 OUT, @url, 'qa_output/chunk1.dat'
EXEC sp_OAMethod @task1, 'Run', @success OUT
DECLARE @task2 int
EXEC sp_OAMethod @http2, 'DownloadAsync', @task2 OUT, @url, 'qa_output/chunk2.dat'
EXEC sp_OAMethod @task2, 'Run', @success OUT
DECLARE @task3 int
EXEC sp_OAMethod @http3, 'DownloadAsync', @task3 OUT, @url, 'qa_output/chunk3.dat'
EXEC sp_OAMethod @task3, 'Run', @success OUT
DECLARE @task4 int
EXEC sp_OAMethod @http4, 'DownloadAsync', @task4 OUT, @url, 'qa_output/chunk4.dat'
EXEC sp_OAMethod @task4, 'Run', @success OUT
-- Wait for the downloads to complete.
DECLARE @numLive int
SELECT @numLive = 4
WHILE @numLive > 0
BEGIN
SELECT @numLive = 0
EXEC sp_OAGetProperty @task1, 'Live', @iTmp0 OUT
IF @iTmp0 = 1
BEGIN
SELECT @numLive = @numLive + 1
END
EXEC sp_OAGetProperty @task2, 'Live', @iTmp0 OUT
IF @iTmp0 = 1
BEGIN
SELECT @numLive = @numLive + 1
END
EXEC sp_OAGetProperty @task3, 'Live', @iTmp0 OUT
IF @iTmp0 = 1
BEGIN
SELECT @numLive = @numLive + 1
END
EXEC sp_OAGetProperty @task4, 'Live', @iTmp0 OUT
IF @iTmp0 = 1
BEGIN
SELECT @numLive = @numLive + 1
END
IF @numLive > 0
BEGIN
-- SleepMs is a convenience method to cause the caller to sleep for N millisec.
-- It does not cause the given task to sleep..
EXEC sp_OAMethod @task1, 'SleepMs', NULL, 10
END
END
-- All should be downloaded now..
-- Examine the result of each Download.
DECLARE @numErrors int
SELECT @numErrors = 0
EXEC sp_OAMethod @task1, 'GetResultBool', @iTmp0 OUT
IF @iTmp0 = 0
BEGIN
EXEC sp_OAGetProperty @task1, 'ResultErrorText', @sTmp0 OUT
PRINT @sTmp0
SELECT @numErrors = @numErrors + 1
END
EXEC sp_OAMethod @task2, 'GetResultBool', @iTmp0 OUT
IF @iTmp0 = 0
BEGIN
EXEC sp_OAGetProperty @task2, 'ResultErrorText', @sTmp0 OUT
PRINT @sTmp0
SELECT @numErrors = @numErrors + 1
END
EXEC sp_OAMethod @task3, 'GetResultBool', @iTmp0 OUT
IF @iTmp0 = 0
BEGIN
EXEC sp_OAGetProperty @task3, 'ResultErrorText', @sTmp0 OUT
PRINT @sTmp0
SELECT @numErrors = @numErrors + 1
END
EXEC sp_OAMethod @task4, 'GetResultBool', @iTmp0 OUT
IF @iTmp0 = 0
BEGIN
EXEC sp_OAGetProperty @task4, 'ResultErrorText', @sTmp0 OUT
PRINT @sTmp0
SELECT @numErrors = @numErrors + 1
END
IF @numErrors > 0
BEGIN
EXEC @hr = sp_OADestroy @task1
EXEC @hr = sp_OADestroy @task2
EXEC @hr = sp_OADestroy @task3
EXEC @hr = sp_OADestroy @task4
EXEC @hr = sp_OADestroy @http
EXEC @hr = sp_OADestroy @resp
EXEC @hr = sp_OADestroy @http1
EXEC @hr = sp_OADestroy @http2
EXEC @hr = sp_OADestroy @http3
EXEC @hr = sp_OADestroy @http4
EXEC @hr = sp_OADestroy @sbRange
RETURN
END
-- All downloads were successful.
-- Compose the file from the parts.
DECLARE @fac int
EXEC @hr = sp_OACreate 'Chilkat.FileAccess', @fac OUT
EXEC sp_OAMethod @fac, 'ReassembleFile', @success OUT, 'qa_output', 'chunk', 'dat', 'qa_output/hamlet.xml'
IF @success = 0
BEGIN
EXEC sp_OAGetProperty @fac, 'LastErrorText', @sTmp0 OUT
PRINT @sTmp0
END
ELSE
BEGIN
PRINT 'Success.'
END
EXEC @hr = sp_OADestroy @task1
EXEC @hr = sp_OADestroy @task2
EXEC @hr = sp_OADestroy @task3
EXEC @hr = sp_OADestroy @task4
-- Let's download in the regular way, and then compare files..
EXEC sp_OAMethod @http, 'Download', @success OUT, @url, 'qa_output/hamletRegular.xml'
-- Compare files.
DECLARE @bSame int
EXEC sp_OAMethod @fac, 'FileContentsEqual', @bSame OUT, 'qa_output/hamlet.xml', 'qa_output/hamletRegular.xml'
PRINT 'bSame = ' + @bSame
EXEC @hr = sp_OADestroy @http
EXEC @hr = sp_OADestroy @resp
EXEC @hr = sp_OADestroy @http1
EXEC @hr = sp_OADestroy @http2
EXEC @hr = sp_OADestroy @http3
EXEC @hr = sp_OADestroy @http4
EXEC @hr = sp_OADestroy @sbRange
EXEC @hr = sp_OADestroy @fac
END
GO