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04/02/2012

查詢活動收集器型別

查詢活動收集器型別是查詢統計資料收集組 (其中一個預先定義的系統資料收集組) 所使用的自訂收集器型別。

這個收集器型別可用來收集查詢統計資料和查詢活動資訊，以及符合預先定義準則之查詢的查詢計畫和查詢文字。如果您使用這個收集器型別來建立自己的收集組，它將會與查詢統計資料收集組收集相同的資訊。因此，建議您使用預先定義的查詢統計資料收集組。

架構和處理

查詢活動收集器型別包含下列元素：

輸入參數結構描述 (內部)
收集資料的 SSIS 封裝 (QueryActivityCollect.dtsx)
上傳資料的 SSIS 封裝 (QueryActivityUpload.dtsx)

此外，這個收集器型別會利用自訂工作或轉換來分析和選取要儲存在管理資料倉儲中的資料。

查詢活動收集器型別會執行下列作業：

它會收集 dm_exec_requests、dm_exec_sessions 和其他選取之相關動態管理檢視的範例。這項作業會實作成單一聯結的查詢。資料收集會依照針對收集項所指定的頻率進行。
它會依照等於收集組上傳頻率的頻率來收集 dm_exec_query_stats 動態管理檢視的快照集。根據預設，查詢統計資料收集組的上傳頻率為 15 分鐘。

收集階段

下表將顯示收集階段期間所使用的查詢。這項查詢定義於 QueryActivityCollect.dtsx SSIS 封裝中。

收集頻率

10 秒

查詢

SET NOCOUNT ON
-- Get the collection time as UTC time
DECLARE @collection_time datetime
SET @collection_time = GETDATE()
SELECT
CONVERT(int, ROW_NUMBER() OVER (ORDER BY sess.session_id, ISNULL (req.request_id, -1), ISNULL (tasks.exec_context_id, -1)) ) AS row_id,
-- IDs and Blocking IDs
sess.session_id, 
ISNULL (req.request_id, -1) AS request_id, 
ISNULL (tasks.exec_context_id, -1) AS exec_context_id, 
ISNULL (req.blocking_session_id, 0) AS blocking_session_id,
CONVERT (bit, CASE 
                WHEN EXISTS (SELECT TOP 1 session_id FROM sys.dm_exec_requests bl WHERE bl.blocking_session_id = req.session_id) THEN 1
                ELSE 0
              END) AS is_blocking,
ISNULL (waits.blocking_exec_context_id, 0) AS blocking_exec_context_id, 
tasks.scheduler_id, 
DB_NAME(req.database_id) as database_name, 
req.[user_id], 
-- State information
LEFT (tasks.task_state, 10) AS task_state, 
LEFT (req.status, 15) AS request_status, 
LEFT (sess.status, 15) AS session_status,
req.executing_managed_code, 
-- Session information
sess.login_time, 
sess.is_user_process, 
LEFT (ISNULL (sess.[host_name], ''), 20) AS [host_name], 
LEFT (ISNULL (sess.[program_name], ''), 50) AS [program_name], 
LEFT (ISNULL (sess.login_name, ''), 30) AS login_name, 
-- Waits information
LEFT (ISNULL (req.wait_type, ''), 45) AS wait_type, 
LEFT (ISNULL (req.last_wait_type, ''), 45) AS last_wait_type, 
ISNULL (waits.wait_duration_ms, 0) AS wait_duration_ms, 
LEFT (ISNULL (req.wait_resource, ''), 50) AS wait_resource, 
LEFT (ISNULL (waits.resource_description, ''), 140) AS resource_description,
-- Transaction information
req.transaction_id, 
ISNULL(req.open_transaction_count, 0) AS open_transaction_count,
COALESCE(req.transaction_isolation_level, sess.transaction_isolation_level) AS transaction_isolation_level,
-- Request stats
req.cpu_time AS request_cpu_time, 
req.logical_reads AS request_logical_reads, 
req.reads AS request_reads, 
req.writes AS request_writes, 
req.total_elapsed_time AS request_total_elapsed_time, 
req.start_time AS request_start_time, 
-- Session stats
sess.memory_usage, 
sess.cpu_time AS session_cpu_time, 
sess.reads AS session_reads, 
sess.writes AS session_writes, 
sess.logical_reads AS session_logical_reads, 
sess.total_scheduled_time AS session_total_scheduled_time, 
sess.total_elapsed_time AS session_total_elapsed_time, 
sess.last_request_start_time, 
sess.last_request_end_time, 
req.open_resultset_count AS open_resultsets, 
sess.row_count AS session_row_count, 
sess.prev_error, 
tasks.pending_io_count, 
-- Text/Plan handles
ISNULL (req.command, 'AWAITING COMMAND') AS command,  
req.plan_handle, 
req.sql_handle, 
req.statement_start_offset, 
req.statement_end_offset,
@collection_time AS collection_time
FROM sys.dm_exec_sessions sess 
LEFT OUTER MERGE JOIN sys.dm_exec_requests req  ON sess.session_id = req.session_id
LEFT OUTER MERGE JOIN sys.dm_os_tasks tasks ON tasks.session_id = sess.session_id AND tasks.request_id = req.request_id AND tasks.task_address = req.task_address
LEFT OUTER MERGE JOIN sys.dm_os_waiting_tasks waits ON waits.session_id = sess.session_id AND waits.waiting_task_address = req.task_address
WHERE 
    sess.session_id <> @@SPID
    AND
    (
        (req.session_id IS NOT NULL AND (sess.is_user_process = 1 OR req.status COLLATE Latin1_General_BIN NOT IN ('background', 'sleeping')))-- active request
            OR 
        (sess.session_id IN (SELECT DISTINCT blocking_session_id FROM sys.dm_exec_requests WHERE blocking_session_id != 0))            -- not active, but head blocker
    )
OPTION (FORCE ORDER)

上傳階段

在上傳階段期間，系統會分析收集的資料以便判斷哪些資料將儲存在管理資料倉儲中。這項分析會判斷必須儲存的一組查詢統計資料、查詢計畫和查詢文字。

其中的重要元素是一個演算法，它可選取要將哪些查詢和查詢計畫儲存到資料倉儲內。此演算法的運作方式如下：

收集 sys.dm_exec_query_stats 的快照集。它會依照等於收集組上傳頻率的頻率來收集這個快照集 (根據預設，這個頻率是 15 分鐘)。
擷取最近的快照集 (從先前 15 分鐘)，以便與新的快照集比較。最近的快照集會在本機快取，而且不需要從管理資料倉儲加以擷取。
使用下列數據從每個快照集中選取前三個查詢：
- 經過時間
- 工作者時間
- 邏輯讀取次數
- 邏輯寫入次數
- 實體讀取
- 執行計數
此程序會提供 6 x 3 個 sql_handles 和 plan_handles。
識別唯一的 sql_handles 和 plan_handles。
讓這個結果與儲存在資料倉儲內的 sql_handles 和 plan_handles 相交。

如果是新的 sql_handles 和 plan_handles，請從伺服器取得計畫和文字。如果找不到此計畫或文字 (可能已經從本機快取中將它移除)，請將此控制代碼儲存在管理資料倉儲中。
如果是蒐集而來的每一個 sql_handle 文字，請將此文字正規化 (例如，移除參數和常值)，並針對正規化的文字計算唯一的雜湊值。請將正規化的文字、雜湊值及原始 sql_handle 的對應儲存到管理資料倉儲中。

下表將顯示用來取得快照集以及分析和上傳資料至管理資料倉儲的查詢。這項查詢定義於 QueryActivityUpload.dtsx SSIS 封裝中。

查詢

SET NOCOUNT ON
DECLARE @p1 datetime
SET @p1 = GETDATE()
SELECT 
    [sql_handle],
    statement_start_offset,
    statement_end_offset,
    -- Use ISNULL here and in other columns to handle in-progress queries that are not yet in sys.dm_exec_query_stats.  
    -- These values only come from sys.dm_exec_query_stats. If the plan does not show up in sys.dm_exec_query_stats 
    -- (first execution of a still-in-progress query, visible in sys.dm_exec_requests), these values will be NULL. 
    MAX (plan_generation_num) AS plan_generation_num,
    plan_handle,
    MIN (creation_time) AS creation_time, 
    MAX (last_execution_time) AS last_execution_time,
    SUM (execution_count) AS execution_count,
    SUM (total_worker_time) AS total_worker_time,
    MIN (min_worker_time) AS min_worker_time,           -- NULLable
    MAX (max_worker_time) AS max_worker_time,
    SUM (total_physical_reads) AS total_physical_reads,
    MIN (min_physical_reads) AS min_physical_reads,     -- NULLable
    MAX (max_physical_reads) AS max_physical_reads,
    SUM (total_logical_writes) AS total_logical_writes,
    MIN (min_logical_writes) AS min_logical_writes,     -- NULLable
    MAX (max_logical_writes) AS max_logical_writes,
    SUM (total_logical_reads) AS total_logical_reads,
    MIN (min_logical_reads) AS min_logical_reads,       -- NULLable
    MAX (max_logical_reads) AS max_logical_reads,
    SUM (total_clr_time) AS total_clr_time,
    MIN (min_clr_time) AS min_clr_time,                 -- NULLable
    MAX (max_clr_time) AS max_clr_time,
    SUM (total_elapsed_time) AS total_elapsed_time,
    MIN (min_elapsed_time) AS min_elapsed_time,         -- NULLable
    MAX (max_elapsed_time) AS max_elapsed_time,
    @p1 AS collection_time
FROM
(
    SELECT  
        [sql_handle],
        statement_start_offset,
        statement_end_offset,
        plan_generation_num,
        plan_handle,
        creation_time,
        last_execution_time,
        execution_count,
        total_worker_time,
        min_worker_time,
        max_worker_time,
        total_physical_reads,
        min_physical_reads,
        max_physical_reads,
        total_logical_writes,
        min_logical_writes,
        max_logical_writes,
        total_logical_reads,
        min_logical_reads,
        max_logical_reads,
        total_clr_time,
        min_clr_time,
        max_clr_time,
        total_elapsed_time,
        min_elapsed_time,
        max_elapsed_time 
    FROM sys.dm_exec_query_stats AS q
    UNION ALL 
    SELECT 
        r.[sql_handle],
        r.statement_start_offset,
        r.statement_end_offset,
        ISNULL (qs.plan_generation_num, 0) AS plan_generation_num,
        r.plan_handle,
        ISNULL (qs.creation_time, r.start_time) AS creation_time,
        r.start_time AS last_execution_time,
        1 AS execution_count,
        r.cpu_time AS total_worker_time,
        qs.min_worker_time,     -- min should not be influenced by in-progress queries
        r.cpu_time AS max_worker_time,
        r.reads AS total_physical_reads,
        qs.min_physical_reads,  -- min should not be influenced by in-progress queries
        r.reads AS max_physical_reads,
        r.writes AS total_logical_writes,
        qs.min_logical_writes,  -- min should not be influenced by in-progress queries
        r.writes AS max_logical_writes,
        r.logical_reads AS total_logical_reads,
        qs.min_logical_reads,   -- min should not be influenced by in-progress queries
        r.logical_reads AS max_logical_reads,
        qs.total_clr_time,      -- CLR time is not available in dm_exec_requests
        qs.min_clr_time,        -- CLR time is not available in dm_exec_requests
        qs.max_clr_time,        -- CLR time is not available in dm_exec_requests
        r.total_elapsed_time AS total_elapsed_time,
        qs.min_elapsed_time,    -- min should not be influenced by in-progress queries
        r.total_elapsed_time AS max_elapsed_time
    FROM sys.dm_exec_requests AS r 
    LEFT OUTER JOIN sys.dm_exec_query_stats AS qs ON r.plan_handle = qs.plan_handle AND r.statement_start_offset = qs.statement_start_offset 
        AND r.statement_end_offset = qs.statement_end_offset 
    WHERE r.sql_handle IS NOT NULL 
) AS query_stats 
OUTER APPLY sys.dm_exec_sql_text (sql_handle) AS sql
GROUP BY [sql_handle], plan_handle, statement_start_offset, statement_end_offset 
ORDER BY [sql_handle], plan_handle, statement_start_offset, statement_end_offset

查詢輸出

snapshots.query_stats、snapshots.notable_query_text 和 snapshots.notable_query_plan